[libcamera-devel,v7,10/11] libcamera: stream: Remove bufferCount

13084 diff mbox series

Now that the number of buffers allocated by the FrameBufferAllocator
helper is passed through FrameBufferAllocator::allocate() and the
pipelines no longer use bufferCount for internal buffer or V4L2 buffer
slots allocation, we no longer need to have bufferCount in the
StreamConfiguration, so remove it.

Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
---

No changes in v7

Changes in v6:
- Removed IPU3_BUFFER_COUNT as it was unused

 include/libcamera/stream.h                         |  2 --
 src/android/camera_stream.cpp                      |  2 +-
 src/libcamera/pipeline/ipu3/cio2.cpp               |  1 -
 src/libcamera/pipeline/ipu3/ipu3.cpp               |  8 --------
 src/libcamera/pipeline/raspberrypi/raspberrypi.cpp |  6 ------
 src/libcamera/pipeline/rkisp1/rkisp1_path.cpp      |  2 --
 src/libcamera/pipeline/simple/converter.cpp        |  3 ---
 src/libcamera/pipeline/simple/converter.h          |  3 ---
 src/libcamera/pipeline/simple/simple.cpp           |  5 +----
 src/libcamera/pipeline/uvcvideo/uvcvideo.cpp       |  3 ---
 src/libcamera/pipeline/vimc/vimc.cpp               |  3 ---
 src/libcamera/stream.cpp                           |  9 ++-------
 src/v4l2/v4l2_camera.cpp                           | 14 ++++++++++----
 src/v4l2/v4l2_camera.h                             |  5 +++--
 src/v4l2/v4l2_camera_proxy.cpp                     |  8 +++-----
 test/camera/buffer_import.cpp                      | 10 +++++++---
 test/libtest/buffer_source.cpp                     |  4 ++--
 test/libtest/buffer_source.h                       |  2 +-
 test/v4l2_videodevice/buffer_cache.cpp             |  4 ++--
 19 files changed, 32 insertions(+), 62 deletions(-)

Hi Nicolas

Thanks very much for all this work! I was wondering if I could ask a
little more about this patch. In our applications, for example, we set
the bufferCount according to the use-case that the application is
implementing. For example:

* For preview windows we set bufferCount to 4.
* For video capture we drop fewer frames with a deeper queue so we set it to 6.
* For stills capture we can get by with one frame, though use cases
that capture several stills images for fusion work better if we set
bufferCount to 2 or 3.

I was wondering how our applications can achieve this behaviour if the
bufferCount field is no longer available.

Thanks!
David

On Fri, 23 Jul 2021 at 00:29, Nícolas F. R. A. Prado
<nfraprado@collabora.com> wrote:
>
> Now that the number of buffers allocated by the FrameBufferAllocator
> helper is passed through FrameBufferAllocator::allocate() and the
> pipelines no longer use bufferCount for internal buffer or V4L2 buffer
> slots allocation, we no longer need to have bufferCount in the
> StreamConfiguration, so remove it.
>
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> ---
>
> No changes in v7
>
> Changes in v6:
> - Removed IPU3_BUFFER_COUNT as it was unused
>
>  include/libcamera/stream.h                         |  2 --
>  src/android/camera_stream.cpp                      |  2 +-
>  src/libcamera/pipeline/ipu3/cio2.cpp               |  1 -
>  src/libcamera/pipeline/ipu3/ipu3.cpp               |  8 --------
>  src/libcamera/pipeline/raspberrypi/raspberrypi.cpp |  6 ------
>  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp      |  2 --
>  src/libcamera/pipeline/simple/converter.cpp        |  3 ---
>  src/libcamera/pipeline/simple/converter.h          |  3 ---
>  src/libcamera/pipeline/simple/simple.cpp           |  5 +----
>  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp       |  3 ---
>  src/libcamera/pipeline/vimc/vimc.cpp               |  3 ---
>  src/libcamera/stream.cpp                           |  9 ++-------
>  src/v4l2/v4l2_camera.cpp                           | 14 ++++++++++----
>  src/v4l2/v4l2_camera.h                             |  5 +++--
>  src/v4l2/v4l2_camera_proxy.cpp                     |  8 +++-----
>  test/camera/buffer_import.cpp                      | 10 +++++++---
>  test/libtest/buffer_source.cpp                     |  4 ++--
>  test/libtest/buffer_source.h                       |  2 +-
>  test/v4l2_videodevice/buffer_cache.cpp             |  4 ++--
>  19 files changed, 32 insertions(+), 62 deletions(-)
>
> diff --git a/include/libcamera/stream.h b/include/libcamera/stream.h
> index 0c55e7164592..b25f0059f2f1 100644
> --- a/include/libcamera/stream.h
> +++ b/include/libcamera/stream.h
> @@ -45,8 +45,6 @@ struct StreamConfiguration {
>         unsigned int stride;
>         unsigned int frameSize;
>
> -       unsigned int bufferCount;
> -
>         Stream *stream() const { return stream_; }
>         void setStream(Stream *stream) { stream_ = stream; }
>         const StreamFormats &formats() const { return formats_; }
> diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
> index b168e3c0c288..0794be409f82 100644
> --- a/src/android/camera_stream.cpp
> +++ b/src/android/camera_stream.cpp
> @@ -94,7 +94,7 @@ int CameraStream::configure()
>                         buffers_.push_back(frameBuffer.get());
>         }
>
> -       camera3Stream_->max_buffers = configuration().bufferCount;
> +       camera3Stream_->max_buffers = bufferCount;
>
>         return 0;
>  }
> diff --git a/src/libcamera/pipeline/ipu3/cio2.cpp b/src/libcamera/pipeline/ipu3/cio2.cpp
> index 1bcd580e251c..0e04e7214489 100644
> --- a/src/libcamera/pipeline/ipu3/cio2.cpp
> +++ b/src/libcamera/pipeline/ipu3/cio2.cpp
> @@ -214,7 +214,6 @@ StreamConfiguration CIO2Device::generateConfiguration(Size size) const
>
>         cfg.size = sensorFormat.size;
>         cfg.pixelFormat = mbusCodesToPixelFormat.at(sensorFormat.mbus_code);
> -       cfg.bufferCount = CIO2_BUFFER_COUNT;
>
>         return cfg;
>  }
> diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> index 4efd201c05e5..b223b3f33cd0 100644
> --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> @@ -38,7 +38,6 @@ namespace libcamera {
>
>  LOG_DEFINE_CATEGORY(IPU3)
>
> -static constexpr unsigned int IPU3_BUFFER_COUNT = 4;
>  static constexpr unsigned int IPU3_MAX_STREAMS = 3;
>  static const Size IMGU_OUTPUT_MIN_SIZE = { 2, 2 };
>  static const Size IMGU_OUTPUT_MAX_SIZE = { 4480, 34004 };
> @@ -295,7 +294,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
>                         /* Initialize the RAW stream with the CIO2 configuration. */
>                         cfg->size = cio2Configuration_.size;
>                         cfg->pixelFormat = cio2Configuration_.pixelFormat;
> -                       cfg->bufferCount = cio2Configuration_.bufferCount;
>                         cfg->stride = info.stride(cfg->size.width, 0, 64);
>                         cfg->frameSize = info.frameSize(cfg->size, 64);
>                         cfg->setStream(const_cast<Stream *>(&data_->rawStream_));
> @@ -339,7 +337,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
>                                               IMGU_OUTPUT_HEIGHT_ALIGN);
>
>                         cfg->pixelFormat = formats::NV12;
> -                       cfg->bufferCount = IPU3_BUFFER_COUNT;
>                         cfg->stride = info.stride(cfg->size.width, 0, 1);
>                         cfg->frameSize = info.frameSize(cfg->size, 1);
>
> @@ -407,7 +404,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
>         Size sensorResolution = data->cio2_.sensor()->resolution();
>         for (const StreamRole role : roles) {
>                 std::map<PixelFormat, std::vector<SizeRange>> streamFormats;
> -               unsigned int bufferCount;
>                 PixelFormat pixelFormat;
>                 Size size;
>
> @@ -428,7 +424,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
>                         size.height = utils::alignDown(size.height - 1,
>                                                        IMGU_OUTPUT_HEIGHT_MARGIN);
>                         pixelFormat = formats::NV12;
> -                       bufferCount = IPU3_BUFFER_COUNT;
>                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
>
>                         break;
> @@ -438,7 +433,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
>                                 data->cio2_.generateConfiguration(sensorResolution);
>                         pixelFormat = cio2Config.pixelFormat;
>                         size = cio2Config.size;
> -                       bufferCount = cio2Config.bufferCount;
>
>                         for (const PixelFormat &format : data->cio2_.formats())
>                                 streamFormats[format] = data->cio2_.sizes();
> @@ -457,7 +451,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
>                                                .alignedDownTo(IMGU_OUTPUT_WIDTH_ALIGN,
>                                                               IMGU_OUTPUT_HEIGHT_ALIGN);
>                         pixelFormat = formats::NV12;
> -                       bufferCount = IPU3_BUFFER_COUNT;
>                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
>
>                         break;
> @@ -474,7 +467,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
>                 StreamConfiguration cfg(formats);
>                 cfg.size = size;
>                 cfg.pixelFormat = pixelFormat;
> -               cfg.bufferCount = bufferCount;
>                 config->addConfiguration(cfg);
>         }
>
> diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> index 776e0f92aed1..e6fc0425c3ef 100644
> --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> @@ -473,7 +473,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
>         RPiCameraData *data = cameraData(camera);
>         CameraConfiguration *config = new RPiCameraConfiguration(data);
>         V4L2DeviceFormat sensorFormat;
> -       unsigned int bufferCount;
>         PixelFormat pixelFormat;
>         V4L2VideoDevice::Formats fmts;
>         Size size;
> @@ -491,7 +490,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
>                         sensorFormat = findBestMode(fmts, size);
>                         pixelFormat = sensorFormat.fourcc.toPixelFormat();
>                         ASSERT(pixelFormat.isValid());
> -                       bufferCount = 2;
>                         rawCount++;
>                         break;
>
> @@ -500,7 +498,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
>                         pixelFormat = formats::NV12;
>                         /* Return the largest sensor resolution. */
>                         size = data->sensor_->resolution();
> -                       bufferCount = 1;
>                         outCount++;
>                         break;
>
> @@ -516,7 +513,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
>                         fmts = data->isp_[Isp::Output0].dev()->formats();
>                         pixelFormat = formats::YUV420;
>                         size = { 1920, 1080 };
> -                       bufferCount = 4;
>                         outCount++;
>                         break;
>
> @@ -524,7 +520,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
>                         fmts = data->isp_[Isp::Output0].dev()->formats();
>                         pixelFormat = formats::ARGB8888;
>                         size = { 800, 600 };
> -                       bufferCount = 4;
>                         outCount++;
>                         break;
>
> @@ -554,7 +549,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
>                 StreamConfiguration cfg(formats);
>                 cfg.size = size;
>                 cfg.pixelFormat = pixelFormat;
> -               cfg.bufferCount = bufferCount;
>                 config->addConfiguration(cfg);
>         }
>
> diff --git a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> index fea330f72886..4961f3971e59 100644
> --- a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> +++ b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> @@ -61,7 +61,6 @@ StreamConfiguration RkISP1Path::generateConfiguration(const Size &resolution)
>         StreamConfiguration cfg(formats);
>         cfg.pixelFormat = formats::NV12;
>         cfg.size = maxResolution;
> -       cfg.bufferCount = RKISP1_BUFFER_COUNT;
>
>         return cfg;
>  }
> @@ -77,7 +76,6 @@ CameraConfiguration::Status RkISP1Path::validate(StreamConfiguration *cfg)
>
>         cfg->size.boundTo(maxResolution_);
>         cfg->size.expandTo(minResolution_);
> -       cfg->bufferCount = RKISP1_BUFFER_COUNT;
>
>         V4L2DeviceFormat format;
>         format.fourcc = video_->toV4L2PixelFormat(cfg->pixelFormat);
> diff --git a/src/libcamera/pipeline/simple/converter.cpp b/src/libcamera/pipeline/simple/converter.cpp
> index b3bcf01483f7..fda417793e80 100644
> --- a/src/libcamera/pipeline/simple/converter.cpp
> +++ b/src/libcamera/pipeline/simple/converter.cpp
> @@ -89,9 +89,6 @@ int SimpleConverter::Stream::configure(const StreamConfiguration &inputCfg,
>                 return -EINVAL;
>         }
>
> -       inputBufferCount_ = inputCfg.bufferCount;
> -       outputBufferCount_ = outputCfg.bufferCount;
> -
>         return 0;
>  }
>
> diff --git a/src/libcamera/pipeline/simple/converter.h b/src/libcamera/pipeline/simple/converter.h
> index 7e1d60674f62..406e63ca2a80 100644
> --- a/src/libcamera/pipeline/simple/converter.h
> +++ b/src/libcamera/pipeline/simple/converter.h
> @@ -87,9 +87,6 @@ private:
>                 SimpleConverter *converter_;
>                 unsigned int index_;
>                 std::unique_ptr<V4L2M2MDevice> m2m_;
> -
> -               unsigned int inputBufferCount_;
> -               unsigned int outputBufferCount_;
>         };
>
>         std::string deviceNode_;
> diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> index a1163eaf8be2..ded04914f610 100644
> --- a/src/libcamera/pipeline/simple/simple.cpp
> +++ b/src/libcamera/pipeline/simple/simple.cpp
> @@ -628,7 +628,7 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
>                     cfg.size != pipeConfig_->captureSize)
>                         needConversion_ = true;
>
> -               /* Set the stride, frameSize and bufferCount. */
> +               /* Set the stride and frameSize. */
>                 if (needConversion_) {
>                         std::tie(cfg.stride, cfg.frameSize) =
>                                 converter->strideAndFrameSize(cfg.pixelFormat, cfg.size);
> @@ -646,8 +646,6 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
>                         cfg.stride = format.planes[0].bpl;
>                         cfg.frameSize = format.planes[0].size;
>                 }
> -
> -               cfg.bufferCount = 3;
>         }
>
>         return status;
> @@ -770,7 +768,6 @@ int SimplePipelineHandler::configure(Camera *camera, CameraConfiguration *c)
>         inputCfg.pixelFormat = pipeConfig->captureFormat;
>         inputCfg.size = pipeConfig->captureSize;
>         inputCfg.stride = captureFormat.planes[0].bpl;
> -       inputCfg.bufferCount = kNumInternalBuffers;
>
>         return converter_->configure(inputCfg, outputCfgs);
>  }
> diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> index 755949e7a59a..32482300f09a 100644
> --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> @@ -150,8 +150,6 @@ CameraConfiguration::Status UVCCameraConfiguration::validate()
>                 status = Adjusted;
>         }
>
> -       cfg.bufferCount = 4;
> -
>         V4L2DeviceFormat format;
>         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
>         format.size = cfg.size;
> @@ -193,7 +191,6 @@ CameraConfiguration *PipelineHandlerUVC::generateConfiguration(Camera *camera,
>
>         cfg.pixelFormat = formats.pixelformats().front();
>         cfg.size = formats.sizes(cfg.pixelFormat).back();
> -       cfg.bufferCount = 4;
>
>         config->addConfiguration(cfg);
>
> diff --git a/src/libcamera/pipeline/vimc/vimc.cpp b/src/libcamera/pipeline/vimc/vimc.cpp
> index 24ba743a946c..a698427c4361 100644
> --- a/src/libcamera/pipeline/vimc/vimc.cpp
> +++ b/src/libcamera/pipeline/vimc/vimc.cpp
> @@ -167,8 +167,6 @@ CameraConfiguration::Status VimcCameraConfiguration::validate()
>                 status = Adjusted;
>         }
>
> -       cfg.bufferCount = 4;
> -
>         V4L2DeviceFormat format;
>         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
>         format.size = cfg.size;
> @@ -224,7 +222,6 @@ CameraConfiguration *PipelineHandlerVimc::generateConfiguration(Camera *camera,
>
>         cfg.pixelFormat = formats::BGR888;
>         cfg.size = { 1920, 1080 };
> -       cfg.bufferCount = 4;
>
>         config->addConfiguration(cfg);
>
> diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
> index b8626775d224..ca507b72b26a 100644
> --- a/src/libcamera/stream.cpp
> +++ b/src/libcamera/stream.cpp
> @@ -280,7 +280,7 @@ SizeRange StreamFormats::range(const PixelFormat &pixelformat) const
>   * handlers provide StreamFormats.
>   */
>  StreamConfiguration::StreamConfiguration()
> -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> +       : pixelFormat(0), stride(0), frameSize(0),
>           stream_(nullptr)
>  {
>  }
> @@ -289,7 +289,7 @@ StreamConfiguration::StreamConfiguration()
>   * \brief Construct a configuration with stream formats
>   */
>  StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> +       : pixelFormat(0), stride(0), frameSize(0),
>           stream_(nullptr), formats_(formats)
>  {
>  }
> @@ -324,11 +324,6 @@ StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
>   * validating the configuration with a call to CameraConfiguration::validate().
>   */
>
> -/**
> - * \var StreamConfiguration::bufferCount
> - * \brief Requested number of buffers to allocate for the stream
> - */
> -
>  /**
>   * \fn StreamConfiguration::stream()
>   * \brief Retrieve the stream associated with the configuration
> diff --git a/src/v4l2/v4l2_camera.cpp b/src/v4l2/v4l2_camera.cpp
> index d01eacfa2b84..2ff9affc6388 100644
> --- a/src/v4l2/v4l2_camera.cpp
> +++ b/src/v4l2/v4l2_camera.cpp
> @@ -12,6 +12,8 @@
>
>  #include <libcamera/base/log.h>
>
> +#include <libcamera/property_ids.h>
> +
>  using namespace libcamera;
>
>  LOG_DECLARE_CATEGORY(V4L2Compat)
> @@ -107,14 +109,12 @@ void V4L2Camera::requestComplete(Request *request)
>  }
>
>  int V4L2Camera::configure(StreamConfiguration *streamConfigOut,
> -                         const Size &size, const PixelFormat &pixelformat,
> -                         unsigned int bufferCount)
> +                         const Size &size, const PixelFormat &pixelformat)
>  {
>         StreamConfiguration &streamConfig = config_->at(0);
>         streamConfig.size.width = size.width;
>         streamConfig.size.height = size.height;
>         streamConfig.pixelFormat = pixelformat;
> -       streamConfig.bufferCount = bufferCount;
>         /* \todo memoryType (interval vs external) */
>
>         CameraConfiguration::Status validation = config_->validate();
> @@ -146,7 +146,6 @@ int V4L2Camera::validateConfiguration(const PixelFormat &pixelFormat,
>         StreamConfiguration &cfg = config->at(0);
>         cfg.size = size;
>         cfg.pixelFormat = pixelFormat;
> -       cfg.bufferCount = 1;
>
>         CameraConfiguration::Status validation = config->validate();
>         if (validation == CameraConfiguration::Invalid)
> @@ -299,3 +298,10 @@ bool V4L2Camera::isRunning()
>  {
>         return isRunning_;
>  }
> +
> +unsigned int V4L2Camera::minimumRequests(unsigned int count)
> +{
> +       unsigned int min = camera_->properties().get(properties::MinimumRequests);
> +
> +       return std::max(count, min);
> +}
> diff --git a/src/v4l2/v4l2_camera.h b/src/v4l2/v4l2_camera.h
> index a095f4e27524..4b5618ac12b5 100644
> --- a/src/v4l2/v4l2_camera.h
> +++ b/src/v4l2/v4l2_camera.h
> @@ -45,8 +45,7 @@ public:
>         std::vector<Buffer> completedBuffers();
>
>         int configure(StreamConfiguration *streamConfigOut,
> -                     const Size &size, const PixelFormat &pixelformat,
> -                     unsigned int bufferCount);
> +                     const Size &size, const PixelFormat &pixelformat);
>         int validateConfiguration(const PixelFormat &pixelformat,
>                                   const Size &size,
>                                   StreamConfiguration *streamConfigOut);
> @@ -65,6 +64,8 @@ public:
>
>         bool isRunning();
>
> +       unsigned int minimumRequests(unsigned int count);
> +
>  private:
>         void requestComplete(Request *request);
>
> diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
> index 7682c4bddf90..634ec84e0cbb 100644
> --- a/src/v4l2/v4l2_camera_proxy.cpp
> +++ b/src/v4l2/v4l2_camera_proxy.cpp
> @@ -349,8 +349,7 @@ int V4L2CameraProxy::vidioc_s_fmt(V4L2CameraFile *file, struct v4l2_format *arg)
>         Size size(arg->fmt.pix.width, arg->fmt.pix.height);
>         V4L2PixelFormat v4l2Format = V4L2PixelFormat(arg->fmt.pix.pixelformat);
>         ret = vcam_->configure(&streamConfig_, size,
> -                              PixelFormatInfo::info(v4l2Format).format,
> -                              bufferCount_);
> +                              PixelFormatInfo::info(v4l2Format).format);
>         if (ret < 0)
>                 return -EINVAL;
>
> @@ -491,14 +490,13 @@ int V4L2CameraProxy::vidioc_reqbufs(V4L2CameraFile *file, struct v4l2_requestbuf
>         Size size(v4l2PixFormat_.width, v4l2PixFormat_.height);
>         V4L2PixelFormat v4l2Format = V4L2PixelFormat(v4l2PixFormat_.pixelformat);
>         int ret = vcam_->configure(&streamConfig_, size,
> -                                  PixelFormatInfo::info(v4l2Format).format,
> -                                  arg->count);
> +                                  PixelFormatInfo::info(v4l2Format).format);
>         if (ret < 0)
>                 return -EINVAL;
>
>         setFmtFromConfig(streamConfig_);
>
> -       arg->count = streamConfig_.bufferCount;
> +       arg->count = vcam_->minimumRequests(arg->count);
>         bufferCount_ = arg->count;
>
>         ret = vcam_->allocBuffers(arg->count);
> diff --git a/test/camera/buffer_import.cpp b/test/camera/buffer_import.cpp
> index c504ea09e64b..67ac0ad20e15 100644
> --- a/test/camera/buffer_import.cpp
> +++ b/test/camera/buffer_import.cpp
> @@ -16,6 +16,8 @@
>  #include <libcamera/base/thread.h>
>  #include <libcamera/base/timer.h>
>
> +#include <libcamera/property_ids.h>
> +
>  #include "libcamera/internal/device_enumerator.h"
>  #include "libcamera/internal/media_device.h"
>  #include "libcamera/internal/v4l2_videodevice.h"
> @@ -92,10 +94,12 @@ protected:
>                         return TestFail;
>                 }
>
> +               unsigned int bufferCount = camera_->properties().get(properties::MinimumRequests);
> +
>                 Stream *stream = cfg.stream();
>
>                 BufferSource source;
> -               int ret = source.allocate(cfg);
> +               int ret = source.allocate(cfg, bufferCount);
>                 if (ret != TestPass)
>                         return ret;
>
> @@ -139,10 +143,10 @@ protected:
>                 while (timer.isRunning())
>                         dispatcher->processEvents();
>
> -               if (completeRequestsCount_ < cfg.bufferCount * 2) {
> +               if (completeRequestsCount_ < bufferCount * 2) {
>                         std::cout << "Failed to capture enough frames (got "
>                                   << completeRequestsCount_ << " expected at least "
> -                                 << cfg.bufferCount * 2 << ")" << std::endl;
> +                                 << bufferCount * 2 << ")" << std::endl;
>                         return TestFail;
>                 }
>
> diff --git a/test/libtest/buffer_source.cpp b/test/libtest/buffer_source.cpp
> index 73563f2fc39d..c3d5286a2462 100644
> --- a/test/libtest/buffer_source.cpp
> +++ b/test/libtest/buffer_source.cpp
> @@ -24,7 +24,7 @@ BufferSource::~BufferSource()
>                 media_->release();
>  }
>
> -int BufferSource::allocate(const StreamConfiguration &config)
> +int BufferSource::allocate(const StreamConfiguration &config, unsigned int count)
>  {
>         /* Locate and open the video device. */
>         std::string videoDeviceName = "vivid-000-vid-out";
> @@ -77,7 +77,7 @@ int BufferSource::allocate(const StreamConfiguration &config)
>                 return TestFail;
>         }
>
> -       if (video->allocateBuffers(config.bufferCount, &buffers_) < 0) {
> +       if (video->allocateBuffers(count, &buffers_) < 0) {
>                 std::cout << "Failed to allocate buffers" << std::endl;
>                 return TestFail;
>         }
> diff --git a/test/libtest/buffer_source.h b/test/libtest/buffer_source.h
> index 14b4770e8d8a..6a18e269a575 100644
> --- a/test/libtest/buffer_source.h
> +++ b/test/libtest/buffer_source.h
> @@ -20,7 +20,7 @@ public:
>         BufferSource();
>         ~BufferSource();
>
> -       int allocate(const StreamConfiguration &config);
> +       int allocate(const StreamConfiguration &config, unsigned int count);
>         const std::vector<std::unique_ptr<FrameBuffer>> &buffers();
>
>  private:
> diff --git a/test/v4l2_videodevice/buffer_cache.cpp b/test/v4l2_videodevice/buffer_cache.cpp
> index b3f2bec11783..07fddfd2617c 100644
> --- a/test/v4l2_videodevice/buffer_cache.cpp
> +++ b/test/v4l2_videodevice/buffer_cache.cpp
> @@ -10,6 +10,7 @@
>  #include <vector>
>
>  #include <libcamera/formats.h>
> +#include <libcamera/property_ids.h>
>  #include <libcamera/stream.h>
>
>  #include "buffer_source.h"
> @@ -145,10 +146,9 @@ public:
>                 StreamConfiguration cfg;
>                 cfg.pixelFormat = formats::YUYV;
>                 cfg.size = Size(600, 800);
> -               cfg.bufferCount = numBuffers;
>
>                 BufferSource source;
> -               int ret = source.allocate(cfg);
> +               int ret = source.allocate(cfg, numBuffers);
>                 if (ret != TestPass)
>                         return ret;
>
> --
> 2.32.0
>

Hi David,

On Fri, Jul 23, 2021 at 09:42:56AM +0100, David Plowman wrote:
> Hi Nicolas
> 
> Thanks very much for all this work! I was wondering if I could ask a
> little more about this patch. In our applications, for example, we set
> the bufferCount according to the use-case that the application is
> implementing. For example:
> 
> * For preview windows we set bufferCount to 4.
> * For video capture we drop fewer frames with a deeper queue so we set it to 6.
> * For stills capture we can get by with one frame, though use cases
> that capture several stills images for fusion work better if we set
> bufferCount to 2 or 3.
> 
> I was wondering how our applications can achieve this behaviour if the
> bufferCount field is no longer available.

Okay, so the short answer is that the applications, knowing their particular use
case, are responsible to provide enough requests to keep the pipeline going. On
the pipeline handler side, it's free to use how many internal buffers it wants.

So in your case, the pipeline handler could still allocate that same number of
internal buffers as you previously did based on bufferCount, but now based
solely on the StreamRole set. The application would then allocate and queue
how many buffers fits the usage. (Note that before the application would call
FrameBufferAllocator::allocate() and it would allocate 'bufferCount' buffers,
but now the function takes a count argument so the application is free to choose
how many) 

Now, I guess it would be nice for the application to be able to query what is a
good number of buffers to use, for example 6 in the video capture of your use
case. At the moment, the only information available is that 1 is the minimum
number of buffers required. So the application would have to know that 6 is a
good number for video capture. Maybe another property could be introduced later
for this recommended amount, but previous discussions suggested this is very use
case dependent, so might not make sense.

I hope this answers the question. If not, I'm still here :).

Thanks,
Nícolas

> 
> Thanks!
> David
> 
> On Fri, 23 Jul 2021 at 00:29, Nícolas F. R. A. Prado
> <nfraprado@collabora.com> wrote:
> >
> > Now that the number of buffers allocated by the FrameBufferAllocator
> > helper is passed through FrameBufferAllocator::allocate() and the
> > pipelines no longer use bufferCount for internal buffer or V4L2 buffer
> > slots allocation, we no longer need to have bufferCount in the
> > StreamConfiguration, so remove it.
> >
> > Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> > ---
> >
> > No changes in v7
> >
> > Changes in v6:
> > - Removed IPU3_BUFFER_COUNT as it was unused
> >
> >  include/libcamera/stream.h                         |  2 --
> >  src/android/camera_stream.cpp                      |  2 +-
> >  src/libcamera/pipeline/ipu3/cio2.cpp               |  1 -
> >  src/libcamera/pipeline/ipu3/ipu3.cpp               |  8 --------
> >  src/libcamera/pipeline/raspberrypi/raspberrypi.cpp |  6 ------
> >  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp      |  2 --
> >  src/libcamera/pipeline/simple/converter.cpp        |  3 ---
> >  src/libcamera/pipeline/simple/converter.h          |  3 ---
> >  src/libcamera/pipeline/simple/simple.cpp           |  5 +----
> >  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp       |  3 ---
> >  src/libcamera/pipeline/vimc/vimc.cpp               |  3 ---
> >  src/libcamera/stream.cpp                           |  9 ++-------
> >  src/v4l2/v4l2_camera.cpp                           | 14 ++++++++++----
> >  src/v4l2/v4l2_camera.h                             |  5 +++--
> >  src/v4l2/v4l2_camera_proxy.cpp                     |  8 +++-----
> >  test/camera/buffer_import.cpp                      | 10 +++++++---
> >  test/libtest/buffer_source.cpp                     |  4 ++--
> >  test/libtest/buffer_source.h                       |  2 +-
> >  test/v4l2_videodevice/buffer_cache.cpp             |  4 ++--
> >  19 files changed, 32 insertions(+), 62 deletions(-)
> >
> > diff --git a/include/libcamera/stream.h b/include/libcamera/stream.h
> > index 0c55e7164592..b25f0059f2f1 100644
> > --- a/include/libcamera/stream.h
> > +++ b/include/libcamera/stream.h
> > @@ -45,8 +45,6 @@ struct StreamConfiguration {
> >         unsigned int stride;
> >         unsigned int frameSize;
> >
> > -       unsigned int bufferCount;
> > -
> >         Stream *stream() const { return stream_; }
> >         void setStream(Stream *stream) { stream_ = stream; }
> >         const StreamFormats &formats() const { return formats_; }
> > diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
> > index b168e3c0c288..0794be409f82 100644
> > --- a/src/android/camera_stream.cpp
> > +++ b/src/android/camera_stream.cpp
> > @@ -94,7 +94,7 @@ int CameraStream::configure()
> >                         buffers_.push_back(frameBuffer.get());
> >         }
> >
> > -       camera3Stream_->max_buffers = configuration().bufferCount;
> > +       camera3Stream_->max_buffers = bufferCount;
> >
> >         return 0;
> >  }
> > diff --git a/src/libcamera/pipeline/ipu3/cio2.cpp b/src/libcamera/pipeline/ipu3/cio2.cpp
> > index 1bcd580e251c..0e04e7214489 100644
> > --- a/src/libcamera/pipeline/ipu3/cio2.cpp
> > +++ b/src/libcamera/pipeline/ipu3/cio2.cpp
> > @@ -214,7 +214,6 @@ StreamConfiguration CIO2Device::generateConfiguration(Size size) const
> >
> >         cfg.size = sensorFormat.size;
> >         cfg.pixelFormat = mbusCodesToPixelFormat.at(sensorFormat.mbus_code);
> > -       cfg.bufferCount = CIO2_BUFFER_COUNT;
> >
> >         return cfg;
> >  }
> > diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > index 4efd201c05e5..b223b3f33cd0 100644
> > --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> > +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > @@ -38,7 +38,6 @@ namespace libcamera {
> >
> >  LOG_DEFINE_CATEGORY(IPU3)
> >
> > -static constexpr unsigned int IPU3_BUFFER_COUNT = 4;
> >  static constexpr unsigned int IPU3_MAX_STREAMS = 3;
> >  static const Size IMGU_OUTPUT_MIN_SIZE = { 2, 2 };
> >  static const Size IMGU_OUTPUT_MAX_SIZE = { 4480, 34004 };
> > @@ -295,7 +294,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> >                         /* Initialize the RAW stream with the CIO2 configuration. */
> >                         cfg->size = cio2Configuration_.size;
> >                         cfg->pixelFormat = cio2Configuration_.pixelFormat;
> > -                       cfg->bufferCount = cio2Configuration_.bufferCount;
> >                         cfg->stride = info.stride(cfg->size.width, 0, 64);
> >                         cfg->frameSize = info.frameSize(cfg->size, 64);
> >                         cfg->setStream(const_cast<Stream *>(&data_->rawStream_));
> > @@ -339,7 +337,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> >                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> >
> >                         cfg->pixelFormat = formats::NV12;
> > -                       cfg->bufferCount = IPU3_BUFFER_COUNT;
> >                         cfg->stride = info.stride(cfg->size.width, 0, 1);
> >                         cfg->frameSize = info.frameSize(cfg->size, 1);
> >
> > @@ -407,7 +404,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> >         Size sensorResolution = data->cio2_.sensor()->resolution();
> >         for (const StreamRole role : roles) {
> >                 std::map<PixelFormat, std::vector<SizeRange>> streamFormats;
> > -               unsigned int bufferCount;
> >                 PixelFormat pixelFormat;
> >                 Size size;
> >
> > @@ -428,7 +424,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> >                         size.height = utils::alignDown(size.height - 1,
> >                                                        IMGU_OUTPUT_HEIGHT_MARGIN);
> >                         pixelFormat = formats::NV12;
> > -                       bufferCount = IPU3_BUFFER_COUNT;
> >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> >
> >                         break;
> > @@ -438,7 +433,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> >                                 data->cio2_.generateConfiguration(sensorResolution);
> >                         pixelFormat = cio2Config.pixelFormat;
> >                         size = cio2Config.size;
> > -                       bufferCount = cio2Config.bufferCount;
> >
> >                         for (const PixelFormat &format : data->cio2_.formats())
> >                                 streamFormats[format] = data->cio2_.sizes();
> > @@ -457,7 +451,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> >                                                .alignedDownTo(IMGU_OUTPUT_WIDTH_ALIGN,
> >                                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> >                         pixelFormat = formats::NV12;
> > -                       bufferCount = IPU3_BUFFER_COUNT;
> >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> >
> >                         break;
> > @@ -474,7 +467,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> >                 StreamConfiguration cfg(formats);
> >                 cfg.size = size;
> >                 cfg.pixelFormat = pixelFormat;
> > -               cfg.bufferCount = bufferCount;
> >                 config->addConfiguration(cfg);
> >         }
> >
> > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > index 776e0f92aed1..e6fc0425c3ef 100644
> > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > @@ -473,7 +473,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> >         RPiCameraData *data = cameraData(camera);
> >         CameraConfiguration *config = new RPiCameraConfiguration(data);
> >         V4L2DeviceFormat sensorFormat;
> > -       unsigned int bufferCount;
> >         PixelFormat pixelFormat;
> >         V4L2VideoDevice::Formats fmts;
> >         Size size;
> > @@ -491,7 +490,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> >                         sensorFormat = findBestMode(fmts, size);
> >                         pixelFormat = sensorFormat.fourcc.toPixelFormat();
> >                         ASSERT(pixelFormat.isValid());
> > -                       bufferCount = 2;
> >                         rawCount++;
> >                         break;
> >
> > @@ -500,7 +498,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> >                         pixelFormat = formats::NV12;
> >                         /* Return the largest sensor resolution. */
> >                         size = data->sensor_->resolution();
> > -                       bufferCount = 1;
> >                         outCount++;
> >                         break;
> >
> > @@ -516,7 +513,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> >                         pixelFormat = formats::YUV420;
> >                         size = { 1920, 1080 };
> > -                       bufferCount = 4;
> >                         outCount++;
> >                         break;
> >
> > @@ -524,7 +520,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> >                         pixelFormat = formats::ARGB8888;
> >                         size = { 800, 600 };
> > -                       bufferCount = 4;
> >                         outCount++;
> >                         break;
> >
> > @@ -554,7 +549,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> >                 StreamConfiguration cfg(formats);
> >                 cfg.size = size;
> >                 cfg.pixelFormat = pixelFormat;
> > -               cfg.bufferCount = bufferCount;
> >                 config->addConfiguration(cfg);
> >         }
> >
> > diff --git a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > index fea330f72886..4961f3971e59 100644
> > --- a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > +++ b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > @@ -61,7 +61,6 @@ StreamConfiguration RkISP1Path::generateConfiguration(const Size &resolution)
> >         StreamConfiguration cfg(formats);
> >         cfg.pixelFormat = formats::NV12;
> >         cfg.size = maxResolution;
> > -       cfg.bufferCount = RKISP1_BUFFER_COUNT;
> >
> >         return cfg;
> >  }
> > @@ -77,7 +76,6 @@ CameraConfiguration::Status RkISP1Path::validate(StreamConfiguration *cfg)
> >
> >         cfg->size.boundTo(maxResolution_);
> >         cfg->size.expandTo(minResolution_);
> > -       cfg->bufferCount = RKISP1_BUFFER_COUNT;
> >
> >         V4L2DeviceFormat format;
> >         format.fourcc = video_->toV4L2PixelFormat(cfg->pixelFormat);
> > diff --git a/src/libcamera/pipeline/simple/converter.cpp b/src/libcamera/pipeline/simple/converter.cpp
> > index b3bcf01483f7..fda417793e80 100644
> > --- a/src/libcamera/pipeline/simple/converter.cpp
> > +++ b/src/libcamera/pipeline/simple/converter.cpp
> > @@ -89,9 +89,6 @@ int SimpleConverter::Stream::configure(const StreamConfiguration &inputCfg,
> >                 return -EINVAL;
> >         }
> >
> > -       inputBufferCount_ = inputCfg.bufferCount;
> > -       outputBufferCount_ = outputCfg.bufferCount;
> > -
> >         return 0;
> >  }
> >
> > diff --git a/src/libcamera/pipeline/simple/converter.h b/src/libcamera/pipeline/simple/converter.h
> > index 7e1d60674f62..406e63ca2a80 100644
> > --- a/src/libcamera/pipeline/simple/converter.h
> > +++ b/src/libcamera/pipeline/simple/converter.h
> > @@ -87,9 +87,6 @@ private:
> >                 SimpleConverter *converter_;
> >                 unsigned int index_;
> >                 std::unique_ptr<V4L2M2MDevice> m2m_;
> > -
> > -               unsigned int inputBufferCount_;
> > -               unsigned int outputBufferCount_;
> >         };
> >
> >         std::string deviceNode_;
> > diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> > index a1163eaf8be2..ded04914f610 100644
> > --- a/src/libcamera/pipeline/simple/simple.cpp
> > +++ b/src/libcamera/pipeline/simple/simple.cpp
> > @@ -628,7 +628,7 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> >                     cfg.size != pipeConfig_->captureSize)
> >                         needConversion_ = true;
> >
> > -               /* Set the stride, frameSize and bufferCount. */
> > +               /* Set the stride and frameSize. */
> >                 if (needConversion_) {
> >                         std::tie(cfg.stride, cfg.frameSize) =
> >                                 converter->strideAndFrameSize(cfg.pixelFormat, cfg.size);
> > @@ -646,8 +646,6 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> >                         cfg.stride = format.planes[0].bpl;
> >                         cfg.frameSize = format.planes[0].size;
> >                 }
> > -
> > -               cfg.bufferCount = 3;
> >         }
> >
> >         return status;
> > @@ -770,7 +768,6 @@ int SimplePipelineHandler::configure(Camera *camera, CameraConfiguration *c)
> >         inputCfg.pixelFormat = pipeConfig->captureFormat;
> >         inputCfg.size = pipeConfig->captureSize;
> >         inputCfg.stride = captureFormat.planes[0].bpl;
> > -       inputCfg.bufferCount = kNumInternalBuffers;
> >
> >         return converter_->configure(inputCfg, outputCfgs);
> >  }
> > diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > index 755949e7a59a..32482300f09a 100644
> > --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > @@ -150,8 +150,6 @@ CameraConfiguration::Status UVCCameraConfiguration::validate()
> >                 status = Adjusted;
> >         }
> >
> > -       cfg.bufferCount = 4;
> > -
> >         V4L2DeviceFormat format;
> >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> >         format.size = cfg.size;
> > @@ -193,7 +191,6 @@ CameraConfiguration *PipelineHandlerUVC::generateConfiguration(Camera *camera,
> >
> >         cfg.pixelFormat = formats.pixelformats().front();
> >         cfg.size = formats.sizes(cfg.pixelFormat).back();
> > -       cfg.bufferCount = 4;
> >
> >         config->addConfiguration(cfg);
> >
> > diff --git a/src/libcamera/pipeline/vimc/vimc.cpp b/src/libcamera/pipeline/vimc/vimc.cpp
> > index 24ba743a946c..a698427c4361 100644
> > --- a/src/libcamera/pipeline/vimc/vimc.cpp
> > +++ b/src/libcamera/pipeline/vimc/vimc.cpp
> > @@ -167,8 +167,6 @@ CameraConfiguration::Status VimcCameraConfiguration::validate()
> >                 status = Adjusted;
> >         }
> >
> > -       cfg.bufferCount = 4;
> > -
> >         V4L2DeviceFormat format;
> >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> >         format.size = cfg.size;
> > @@ -224,7 +222,6 @@ CameraConfiguration *PipelineHandlerVimc::generateConfiguration(Camera *camera,
> >
> >         cfg.pixelFormat = formats::BGR888;
> >         cfg.size = { 1920, 1080 };
> > -       cfg.bufferCount = 4;
> >
> >         config->addConfiguration(cfg);
> >
> > diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
> > index b8626775d224..ca507b72b26a 100644
> > --- a/src/libcamera/stream.cpp
> > +++ b/src/libcamera/stream.cpp
> > @@ -280,7 +280,7 @@ SizeRange StreamFormats::range(const PixelFormat &pixelformat) const
> >   * handlers provide StreamFormats.
> >   */
> >  StreamConfiguration::StreamConfiguration()
> > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > +       : pixelFormat(0), stride(0), frameSize(0),
> >           stream_(nullptr)
> >  {
> >  }
> > @@ -289,7 +289,7 @@ StreamConfiguration::StreamConfiguration()
> >   * \brief Construct a configuration with stream formats
> >   */
> >  StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > +       : pixelFormat(0), stride(0), frameSize(0),
> >           stream_(nullptr), formats_(formats)
> >  {
> >  }
> > @@ -324,11 +324,6 @@ StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> >   * validating the configuration with a call to CameraConfiguration::validate().
> >   */
> >
> > -/**
> > - * \var StreamConfiguration::bufferCount
> > - * \brief Requested number of buffers to allocate for the stream
> > - */
> > -
> >  /**
> >   * \fn StreamConfiguration::stream()
> >   * \brief Retrieve the stream associated with the configuration
> > diff --git a/src/v4l2/v4l2_camera.cpp b/src/v4l2/v4l2_camera.cpp
> > index d01eacfa2b84..2ff9affc6388 100644
> > --- a/src/v4l2/v4l2_camera.cpp
> > +++ b/src/v4l2/v4l2_camera.cpp
> > @@ -12,6 +12,8 @@
> >
> >  #include <libcamera/base/log.h>
> >
> > +#include <libcamera/property_ids.h>
> > +
> >  using namespace libcamera;
> >
> >  LOG_DECLARE_CATEGORY(V4L2Compat)
> > @@ -107,14 +109,12 @@ void V4L2Camera::requestComplete(Request *request)
> >  }
> >
> >  int V4L2Camera::configure(StreamConfiguration *streamConfigOut,
> > -                         const Size &size, const PixelFormat &pixelformat,
> > -                         unsigned int bufferCount)
> > +                         const Size &size, const PixelFormat &pixelformat)
> >  {
> >         StreamConfiguration &streamConfig = config_->at(0);
> >         streamConfig.size.width = size.width;
> >         streamConfig.size.height = size.height;
> >         streamConfig.pixelFormat = pixelformat;
> > -       streamConfig.bufferCount = bufferCount;
> >         /* \todo memoryType (interval vs external) */
> >
> >         CameraConfiguration::Status validation = config_->validate();
> > @@ -146,7 +146,6 @@ int V4L2Camera::validateConfiguration(const PixelFormat &pixelFormat,
> >         StreamConfiguration &cfg = config->at(0);
> >         cfg.size = size;
> >         cfg.pixelFormat = pixelFormat;
> > -       cfg.bufferCount = 1;
> >
> >         CameraConfiguration::Status validation = config->validate();
> >         if (validation == CameraConfiguration::Invalid)
> > @@ -299,3 +298,10 @@ bool V4L2Camera::isRunning()
> >  {
> >         return isRunning_;
> >  }
> > +
> > +unsigned int V4L2Camera::minimumRequests(unsigned int count)
> > +{
> > +       unsigned int min = camera_->properties().get(properties::MinimumRequests);
> > +
> > +       return std::max(count, min);
> > +}
> > diff --git a/src/v4l2/v4l2_camera.h b/src/v4l2/v4l2_camera.h
> > index a095f4e27524..4b5618ac12b5 100644
> > --- a/src/v4l2/v4l2_camera.h
> > +++ b/src/v4l2/v4l2_camera.h
> > @@ -45,8 +45,7 @@ public:
> >         std::vector<Buffer> completedBuffers();
> >
> >         int configure(StreamConfiguration *streamConfigOut,
> > -                     const Size &size, const PixelFormat &pixelformat,
> > -                     unsigned int bufferCount);
> > +                     const Size &size, const PixelFormat &pixelformat);
> >         int validateConfiguration(const PixelFormat &pixelformat,
> >                                   const Size &size,
> >                                   StreamConfiguration *streamConfigOut);
> > @@ -65,6 +64,8 @@ public:
> >
> >         bool isRunning();
> >
> > +       unsigned int minimumRequests(unsigned int count);
> > +
> >  private:
> >         void requestComplete(Request *request);
> >
> > diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
> > index 7682c4bddf90..634ec84e0cbb 100644
> > --- a/src/v4l2/v4l2_camera_proxy.cpp
> > +++ b/src/v4l2/v4l2_camera_proxy.cpp
> > @@ -349,8 +349,7 @@ int V4L2CameraProxy::vidioc_s_fmt(V4L2CameraFile *file, struct v4l2_format *arg)
> >         Size size(arg->fmt.pix.width, arg->fmt.pix.height);
> >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(arg->fmt.pix.pixelformat);
> >         ret = vcam_->configure(&streamConfig_, size,
> > -                              PixelFormatInfo::info(v4l2Format).format,
> > -                              bufferCount_);
> > +                              PixelFormatInfo::info(v4l2Format).format);
> >         if (ret < 0)
> >                 return -EINVAL;
> >
> > @@ -491,14 +490,13 @@ int V4L2CameraProxy::vidioc_reqbufs(V4L2CameraFile *file, struct v4l2_requestbuf
> >         Size size(v4l2PixFormat_.width, v4l2PixFormat_.height);
> >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(v4l2PixFormat_.pixelformat);
> >         int ret = vcam_->configure(&streamConfig_, size,
> > -                                  PixelFormatInfo::info(v4l2Format).format,
> > -                                  arg->count);
> > +                                  PixelFormatInfo::info(v4l2Format).format);
> >         if (ret < 0)
> >                 return -EINVAL;
> >
> >         setFmtFromConfig(streamConfig_);
> >
> > -       arg->count = streamConfig_.bufferCount;
> > +       arg->count = vcam_->minimumRequests(arg->count);
> >         bufferCount_ = arg->count;
> >
> >         ret = vcam_->allocBuffers(arg->count);
> > diff --git a/test/camera/buffer_import.cpp b/test/camera/buffer_import.cpp
> > index c504ea09e64b..67ac0ad20e15 100644
> > --- a/test/camera/buffer_import.cpp
> > +++ b/test/camera/buffer_import.cpp
> > @@ -16,6 +16,8 @@
> >  #include <libcamera/base/thread.h>
> >  #include <libcamera/base/timer.h>
> >
> > +#include <libcamera/property_ids.h>
> > +
> >  #include "libcamera/internal/device_enumerator.h"
> >  #include "libcamera/internal/media_device.h"
> >  #include "libcamera/internal/v4l2_videodevice.h"
> > @@ -92,10 +94,12 @@ protected:
> >                         return TestFail;
> >                 }
> >
> > +               unsigned int bufferCount = camera_->properties().get(properties::MinimumRequests);
> > +
> >                 Stream *stream = cfg.stream();
> >
> >                 BufferSource source;
> > -               int ret = source.allocate(cfg);
> > +               int ret = source.allocate(cfg, bufferCount);
> >                 if (ret != TestPass)
> >                         return ret;
> >
> > @@ -139,10 +143,10 @@ protected:
> >                 while (timer.isRunning())
> >                         dispatcher->processEvents();
> >
> > -               if (completeRequestsCount_ < cfg.bufferCount * 2) {
> > +               if (completeRequestsCount_ < bufferCount * 2) {
> >                         std::cout << "Failed to capture enough frames (got "
> >                                   << completeRequestsCount_ << " expected at least "
> > -                                 << cfg.bufferCount * 2 << ")" << std::endl;
> > +                                 << bufferCount * 2 << ")" << std::endl;
> >                         return TestFail;
> >                 }
> >
> > diff --git a/test/libtest/buffer_source.cpp b/test/libtest/buffer_source.cpp
> > index 73563f2fc39d..c3d5286a2462 100644
> > --- a/test/libtest/buffer_source.cpp
> > +++ b/test/libtest/buffer_source.cpp
> > @@ -24,7 +24,7 @@ BufferSource::~BufferSource()
> >                 media_->release();
> >  }
> >
> > -int BufferSource::allocate(const StreamConfiguration &config)
> > +int BufferSource::allocate(const StreamConfiguration &config, unsigned int count)
> >  {
> >         /* Locate and open the video device. */
> >         std::string videoDeviceName = "vivid-000-vid-out";
> > @@ -77,7 +77,7 @@ int BufferSource::allocate(const StreamConfiguration &config)
> >                 return TestFail;
> >         }
> >
> > -       if (video->allocateBuffers(config.bufferCount, &buffers_) < 0) {
> > +       if (video->allocateBuffers(count, &buffers_) < 0) {
> >                 std::cout << "Failed to allocate buffers" << std::endl;
> >                 return TestFail;
> >         }
> > diff --git a/test/libtest/buffer_source.h b/test/libtest/buffer_source.h
> > index 14b4770e8d8a..6a18e269a575 100644
> > --- a/test/libtest/buffer_source.h
> > +++ b/test/libtest/buffer_source.h
> > @@ -20,7 +20,7 @@ public:
> >         BufferSource();
> >         ~BufferSource();
> >
> > -       int allocate(const StreamConfiguration &config);
> > +       int allocate(const StreamConfiguration &config, unsigned int count);
> >         const std::vector<std::unique_ptr<FrameBuffer>> &buffers();
> >
> >  private:
> > diff --git a/test/v4l2_videodevice/buffer_cache.cpp b/test/v4l2_videodevice/buffer_cache.cpp
> > index b3f2bec11783..07fddfd2617c 100644
> > --- a/test/v4l2_videodevice/buffer_cache.cpp
> > +++ b/test/v4l2_videodevice/buffer_cache.cpp
> > @@ -10,6 +10,7 @@
> >  #include <vector>
> >
> >  #include <libcamera/formats.h>
> > +#include <libcamera/property_ids.h>
> >  #include <libcamera/stream.h>
> >
> >  #include "buffer_source.h"
> > @@ -145,10 +146,9 @@ public:
> >                 StreamConfiguration cfg;
> >                 cfg.pixelFormat = formats::YUYV;
> >                 cfg.size = Size(600, 800);
> > -               cfg.bufferCount = numBuffers;
> >
> >                 BufferSource source;
> > -               int ret = source.allocate(cfg);
> > +               int ret = source.allocate(cfg, numBuffers);
> >                 if (ret != TestPass)
> >                         return ret;
> >
> > --
> > 2.32.0
> >

Hi Nicolas

Thanks for the explanations. I'm still not sure I entirely understand
so perhaps a quick look at how I would have to change my application
code might help? Here's what I have now (I've removed any
"unimportant" bits!):

configuration_ = camera_->generateConfiguration({ StreamRole::StillCapture });
configuration_->at(0).bufferCount = <value I have determined>;
camera_->configure(configuration_.get());
allocator_ = new FrameBufferAllocator(camera_);
Stream *stream = configuration_->at(0).stream();
allocator_->allocate(stream);
// now allocator_->buffers(stream) has the buffers I want!

I guess one thing to note is that the bufferCount value varies with
more than just the StreamRole, and I don't in general trust the
pipeline handler to "know" what I want. Will this still be possible?

Thanks!
David

On Fri, 23 Jul 2021 at 14:10, Nícolas F. R. A. Prado
<nfraprado@collabora.com> wrote:
>
> Hi David,
>
> On Fri, Jul 23, 2021 at 09:42:56AM +0100, David Plowman wrote:
> > Hi Nicolas
> >
> > Thanks very much for all this work! I was wondering if I could ask a
> > little more about this patch. In our applications, for example, we set
> > the bufferCount according to the use-case that the application is
> > implementing. For example:
> >
> > * For preview windows we set bufferCount to 4.
> > * For video capture we drop fewer frames with a deeper queue so we set it to 6.
> > * For stills capture we can get by with one frame, though use cases
> > that capture several stills images for fusion work better if we set
> > bufferCount to 2 or 3.
> >
> > I was wondering how our applications can achieve this behaviour if the
> > bufferCount field is no longer available.
>
> Okay, so the short answer is that the applications, knowing their particular use
> case, are responsible to provide enough requests to keep the pipeline going. On
> the pipeline handler side, it's free to use how many internal buffers it wants.
>
> So in your case, the pipeline handler could still allocate that same number of
> internal buffers as you previously did based on bufferCount, but now based
> solely on the StreamRole set. The application would then allocate and queue
> how many buffers fits the usage. (Note that before the application would call
> FrameBufferAllocator::allocate() and it would allocate 'bufferCount' buffers,
> but now the function takes a count argument so the application is free to choose
> how many)
>
> Now, I guess it would be nice for the application to be able to query what is a
> good number of buffers to use, for example 6 in the video capture of your use
> case. At the moment, the only information available is that 1 is the minimum
> number of buffers required. So the application would have to know that 6 is a
> good number for video capture. Maybe another property could be introduced later
> for this recommended amount, but previous discussions suggested this is very use
> case dependent, so might not make sense.
>
> I hope this answers the question. If not, I'm still here :).
>
> Thanks,
> Nícolas
>
> >
> > Thanks!
> > David
> >
> > On Fri, 23 Jul 2021 at 00:29, Nícolas F. R. A. Prado
> > <nfraprado@collabora.com> wrote:
> > >
> > > Now that the number of buffers allocated by the FrameBufferAllocator
> > > helper is passed through FrameBufferAllocator::allocate() and the
> > > pipelines no longer use bufferCount for internal buffer or V4L2 buffer
> > > slots allocation, we no longer need to have bufferCount in the
> > > StreamConfiguration, so remove it.
> > >
> > > Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> > > ---
> > >
> > > No changes in v7
> > >
> > > Changes in v6:
> > > - Removed IPU3_BUFFER_COUNT as it was unused
> > >
> > >  include/libcamera/stream.h                         |  2 --
> > >  src/android/camera_stream.cpp                      |  2 +-
> > >  src/libcamera/pipeline/ipu3/cio2.cpp               |  1 -
> > >  src/libcamera/pipeline/ipu3/ipu3.cpp               |  8 --------
> > >  src/libcamera/pipeline/raspberrypi/raspberrypi.cpp |  6 ------
> > >  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp      |  2 --
> > >  src/libcamera/pipeline/simple/converter.cpp        |  3 ---
> > >  src/libcamera/pipeline/simple/converter.h          |  3 ---
> > >  src/libcamera/pipeline/simple/simple.cpp           |  5 +----
> > >  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp       |  3 ---
> > >  src/libcamera/pipeline/vimc/vimc.cpp               |  3 ---
> > >  src/libcamera/stream.cpp                           |  9 ++-------
> > >  src/v4l2/v4l2_camera.cpp                           | 14 ++++++++++----
> > >  src/v4l2/v4l2_camera.h                             |  5 +++--
> > >  src/v4l2/v4l2_camera_proxy.cpp                     |  8 +++-----
> > >  test/camera/buffer_import.cpp                      | 10 +++++++---
> > >  test/libtest/buffer_source.cpp                     |  4 ++--
> > >  test/libtest/buffer_source.h                       |  2 +-
> > >  test/v4l2_videodevice/buffer_cache.cpp             |  4 ++--
> > >  19 files changed, 32 insertions(+), 62 deletions(-)
> > >
> > > diff --git a/include/libcamera/stream.h b/include/libcamera/stream.h
> > > index 0c55e7164592..b25f0059f2f1 100644
> > > --- a/include/libcamera/stream.h
> > > +++ b/include/libcamera/stream.h
> > > @@ -45,8 +45,6 @@ struct StreamConfiguration {
> > >         unsigned int stride;
> > >         unsigned int frameSize;
> > >
> > > -       unsigned int bufferCount;
> > > -
> > >         Stream *stream() const { return stream_; }
> > >         void setStream(Stream *stream) { stream_ = stream; }
> > >         const StreamFormats &formats() const { return formats_; }
> > > diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
> > > index b168e3c0c288..0794be409f82 100644
> > > --- a/src/android/camera_stream.cpp
> > > +++ b/src/android/camera_stream.cpp
> > > @@ -94,7 +94,7 @@ int CameraStream::configure()
> > >                         buffers_.push_back(frameBuffer.get());
> > >         }
> > >
> > > -       camera3Stream_->max_buffers = configuration().bufferCount;
> > > +       camera3Stream_->max_buffers = bufferCount;
> > >
> > >         return 0;
> > >  }
> > > diff --git a/src/libcamera/pipeline/ipu3/cio2.cpp b/src/libcamera/pipeline/ipu3/cio2.cpp
> > > index 1bcd580e251c..0e04e7214489 100644
> > > --- a/src/libcamera/pipeline/ipu3/cio2.cpp
> > > +++ b/src/libcamera/pipeline/ipu3/cio2.cpp
> > > @@ -214,7 +214,6 @@ StreamConfiguration CIO2Device::generateConfiguration(Size size) const
> > >
> > >         cfg.size = sensorFormat.size;
> > >         cfg.pixelFormat = mbusCodesToPixelFormat.at(sensorFormat.mbus_code);
> > > -       cfg.bufferCount = CIO2_BUFFER_COUNT;
> > >
> > >         return cfg;
> > >  }
> > > diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > index 4efd201c05e5..b223b3f33cd0 100644
> > > --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > @@ -38,7 +38,6 @@ namespace libcamera {
> > >
> > >  LOG_DEFINE_CATEGORY(IPU3)
> > >
> > > -static constexpr unsigned int IPU3_BUFFER_COUNT = 4;
> > >  static constexpr unsigned int IPU3_MAX_STREAMS = 3;
> > >  static const Size IMGU_OUTPUT_MIN_SIZE = { 2, 2 };
> > >  static const Size IMGU_OUTPUT_MAX_SIZE = { 4480, 34004 };
> > > @@ -295,7 +294,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > >                         /* Initialize the RAW stream with the CIO2 configuration. */
> > >                         cfg->size = cio2Configuration_.size;
> > >                         cfg->pixelFormat = cio2Configuration_.pixelFormat;
> > > -                       cfg->bufferCount = cio2Configuration_.bufferCount;
> > >                         cfg->stride = info.stride(cfg->size.width, 0, 64);
> > >                         cfg->frameSize = info.frameSize(cfg->size, 64);
> > >                         cfg->setStream(const_cast<Stream *>(&data_->rawStream_));
> > > @@ -339,7 +337,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > >                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> > >
> > >                         cfg->pixelFormat = formats::NV12;
> > > -                       cfg->bufferCount = IPU3_BUFFER_COUNT;
> > >                         cfg->stride = info.stride(cfg->size.width, 0, 1);
> > >                         cfg->frameSize = info.frameSize(cfg->size, 1);
> > >
> > > @@ -407,7 +404,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > >         Size sensorResolution = data->cio2_.sensor()->resolution();
> > >         for (const StreamRole role : roles) {
> > >                 std::map<PixelFormat, std::vector<SizeRange>> streamFormats;
> > > -               unsigned int bufferCount;
> > >                 PixelFormat pixelFormat;
> > >                 Size size;
> > >
> > > @@ -428,7 +424,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > >                         size.height = utils::alignDown(size.height - 1,
> > >                                                        IMGU_OUTPUT_HEIGHT_MARGIN);
> > >                         pixelFormat = formats::NV12;
> > > -                       bufferCount = IPU3_BUFFER_COUNT;
> > >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> > >
> > >                         break;
> > > @@ -438,7 +433,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > >                                 data->cio2_.generateConfiguration(sensorResolution);
> > >                         pixelFormat = cio2Config.pixelFormat;
> > >                         size = cio2Config.size;
> > > -                       bufferCount = cio2Config.bufferCount;
> > >
> > >                         for (const PixelFormat &format : data->cio2_.formats())
> > >                                 streamFormats[format] = data->cio2_.sizes();
> > > @@ -457,7 +451,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > >                                                .alignedDownTo(IMGU_OUTPUT_WIDTH_ALIGN,
> > >                                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> > >                         pixelFormat = formats::NV12;
> > > -                       bufferCount = IPU3_BUFFER_COUNT;
> > >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> > >
> > >                         break;
> > > @@ -474,7 +467,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > >                 StreamConfiguration cfg(formats);
> > >                 cfg.size = size;
> > >                 cfg.pixelFormat = pixelFormat;
> > > -               cfg.bufferCount = bufferCount;
> > >                 config->addConfiguration(cfg);
> > >         }
> > >
> > > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > index 776e0f92aed1..e6fc0425c3ef 100644
> > > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > @@ -473,7 +473,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > >         RPiCameraData *data = cameraData(camera);
> > >         CameraConfiguration *config = new RPiCameraConfiguration(data);
> > >         V4L2DeviceFormat sensorFormat;
> > > -       unsigned int bufferCount;
> > >         PixelFormat pixelFormat;
> > >         V4L2VideoDevice::Formats fmts;
> > >         Size size;
> > > @@ -491,7 +490,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > >                         sensorFormat = findBestMode(fmts, size);
> > >                         pixelFormat = sensorFormat.fourcc.toPixelFormat();
> > >                         ASSERT(pixelFormat.isValid());
> > > -                       bufferCount = 2;
> > >                         rawCount++;
> > >                         break;
> > >
> > > @@ -500,7 +498,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > >                         pixelFormat = formats::NV12;
> > >                         /* Return the largest sensor resolution. */
> > >                         size = data->sensor_->resolution();
> > > -                       bufferCount = 1;
> > >                         outCount++;
> > >                         break;
> > >
> > > @@ -516,7 +513,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> > >                         pixelFormat = formats::YUV420;
> > >                         size = { 1920, 1080 };
> > > -                       bufferCount = 4;
> > >                         outCount++;
> > >                         break;
> > >
> > > @@ -524,7 +520,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> > >                         pixelFormat = formats::ARGB8888;
> > >                         size = { 800, 600 };
> > > -                       bufferCount = 4;
> > >                         outCount++;
> > >                         break;
> > >
> > > @@ -554,7 +549,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > >                 StreamConfiguration cfg(formats);
> > >                 cfg.size = size;
> > >                 cfg.pixelFormat = pixelFormat;
> > > -               cfg.bufferCount = bufferCount;
> > >                 config->addConfiguration(cfg);
> > >         }
> > >
> > > diff --git a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > index fea330f72886..4961f3971e59 100644
> > > --- a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > +++ b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > @@ -61,7 +61,6 @@ StreamConfiguration RkISP1Path::generateConfiguration(const Size &resolution)
> > >         StreamConfiguration cfg(formats);
> > >         cfg.pixelFormat = formats::NV12;
> > >         cfg.size = maxResolution;
> > > -       cfg.bufferCount = RKISP1_BUFFER_COUNT;
> > >
> > >         return cfg;
> > >  }
> > > @@ -77,7 +76,6 @@ CameraConfiguration::Status RkISP1Path::validate(StreamConfiguration *cfg)
> > >
> > >         cfg->size.boundTo(maxResolution_);
> > >         cfg->size.expandTo(minResolution_);
> > > -       cfg->bufferCount = RKISP1_BUFFER_COUNT;
> > >
> > >         V4L2DeviceFormat format;
> > >         format.fourcc = video_->toV4L2PixelFormat(cfg->pixelFormat);
> > > diff --git a/src/libcamera/pipeline/simple/converter.cpp b/src/libcamera/pipeline/simple/converter.cpp
> > > index b3bcf01483f7..fda417793e80 100644
> > > --- a/src/libcamera/pipeline/simple/converter.cpp
> > > +++ b/src/libcamera/pipeline/simple/converter.cpp
> > > @@ -89,9 +89,6 @@ int SimpleConverter::Stream::configure(const StreamConfiguration &inputCfg,
> > >                 return -EINVAL;
> > >         }
> > >
> > > -       inputBufferCount_ = inputCfg.bufferCount;
> > > -       outputBufferCount_ = outputCfg.bufferCount;
> > > -
> > >         return 0;
> > >  }
> > >
> > > diff --git a/src/libcamera/pipeline/simple/converter.h b/src/libcamera/pipeline/simple/converter.h
> > > index 7e1d60674f62..406e63ca2a80 100644
> > > --- a/src/libcamera/pipeline/simple/converter.h
> > > +++ b/src/libcamera/pipeline/simple/converter.h
> > > @@ -87,9 +87,6 @@ private:
> > >                 SimpleConverter *converter_;
> > >                 unsigned int index_;
> > >                 std::unique_ptr<V4L2M2MDevice> m2m_;
> > > -
> > > -               unsigned int inputBufferCount_;
> > > -               unsigned int outputBufferCount_;
> > >         };
> > >
> > >         std::string deviceNode_;
> > > diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> > > index a1163eaf8be2..ded04914f610 100644
> > > --- a/src/libcamera/pipeline/simple/simple.cpp
> > > +++ b/src/libcamera/pipeline/simple/simple.cpp
> > > @@ -628,7 +628,7 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> > >                     cfg.size != pipeConfig_->captureSize)
> > >                         needConversion_ = true;
> > >
> > > -               /* Set the stride, frameSize and bufferCount. */
> > > +               /* Set the stride and frameSize. */
> > >                 if (needConversion_) {
> > >                         std::tie(cfg.stride, cfg.frameSize) =
> > >                                 converter->strideAndFrameSize(cfg.pixelFormat, cfg.size);
> > > @@ -646,8 +646,6 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> > >                         cfg.stride = format.planes[0].bpl;
> > >                         cfg.frameSize = format.planes[0].size;
> > >                 }
> > > -
> > > -               cfg.bufferCount = 3;
> > >         }
> > >
> > >         return status;
> > > @@ -770,7 +768,6 @@ int SimplePipelineHandler::configure(Camera *camera, CameraConfiguration *c)
> > >         inputCfg.pixelFormat = pipeConfig->captureFormat;
> > >         inputCfg.size = pipeConfig->captureSize;
> > >         inputCfg.stride = captureFormat.planes[0].bpl;
> > > -       inputCfg.bufferCount = kNumInternalBuffers;
> > >
> > >         return converter_->configure(inputCfg, outputCfgs);
> > >  }
> > > diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > index 755949e7a59a..32482300f09a 100644
> > > --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > @@ -150,8 +150,6 @@ CameraConfiguration::Status UVCCameraConfiguration::validate()
> > >                 status = Adjusted;
> > >         }
> > >
> > > -       cfg.bufferCount = 4;
> > > -
> > >         V4L2DeviceFormat format;
> > >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> > >         format.size = cfg.size;
> > > @@ -193,7 +191,6 @@ CameraConfiguration *PipelineHandlerUVC::generateConfiguration(Camera *camera,
> > >
> > >         cfg.pixelFormat = formats.pixelformats().front();
> > >         cfg.size = formats.sizes(cfg.pixelFormat).back();
> > > -       cfg.bufferCount = 4;
> > >
> > >         config->addConfiguration(cfg);
> > >
> > > diff --git a/src/libcamera/pipeline/vimc/vimc.cpp b/src/libcamera/pipeline/vimc/vimc.cpp
> > > index 24ba743a946c..a698427c4361 100644
> > > --- a/src/libcamera/pipeline/vimc/vimc.cpp
> > > +++ b/src/libcamera/pipeline/vimc/vimc.cpp
> > > @@ -167,8 +167,6 @@ CameraConfiguration::Status VimcCameraConfiguration::validate()
> > >                 status = Adjusted;
> > >         }
> > >
> > > -       cfg.bufferCount = 4;
> > > -
> > >         V4L2DeviceFormat format;
> > >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> > >         format.size = cfg.size;
> > > @@ -224,7 +222,6 @@ CameraConfiguration *PipelineHandlerVimc::generateConfiguration(Camera *camera,
> > >
> > >         cfg.pixelFormat = formats::BGR888;
> > >         cfg.size = { 1920, 1080 };
> > > -       cfg.bufferCount = 4;
> > >
> > >         config->addConfiguration(cfg);
> > >
> > > diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
> > > index b8626775d224..ca507b72b26a 100644
> > > --- a/src/libcamera/stream.cpp
> > > +++ b/src/libcamera/stream.cpp
> > > @@ -280,7 +280,7 @@ SizeRange StreamFormats::range(const PixelFormat &pixelformat) const
> > >   * handlers provide StreamFormats.
> > >   */
> > >  StreamConfiguration::StreamConfiguration()
> > > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > > +       : pixelFormat(0), stride(0), frameSize(0),
> > >           stream_(nullptr)
> > >  {
> > >  }
> > > @@ -289,7 +289,7 @@ StreamConfiguration::StreamConfiguration()
> > >   * \brief Construct a configuration with stream formats
> > >   */
> > >  StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > > +       : pixelFormat(0), stride(0), frameSize(0),
> > >           stream_(nullptr), formats_(formats)
> > >  {
> > >  }
> > > @@ -324,11 +324,6 @@ StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > >   * validating the configuration with a call to CameraConfiguration::validate().
> > >   */
> > >
> > > -/**
> > > - * \var StreamConfiguration::bufferCount
> > > - * \brief Requested number of buffers to allocate for the stream
> > > - */
> > > -
> > >  /**
> > >   * \fn StreamConfiguration::stream()
> > >   * \brief Retrieve the stream associated with the configuration
> > > diff --git a/src/v4l2/v4l2_camera.cpp b/src/v4l2/v4l2_camera.cpp
> > > index d01eacfa2b84..2ff9affc6388 100644
> > > --- a/src/v4l2/v4l2_camera.cpp
> > > +++ b/src/v4l2/v4l2_camera.cpp
> > > @@ -12,6 +12,8 @@
> > >
> > >  #include <libcamera/base/log.h>
> > >
> > > +#include <libcamera/property_ids.h>
> > > +
> > >  using namespace libcamera;
> > >
> > >  LOG_DECLARE_CATEGORY(V4L2Compat)
> > > @@ -107,14 +109,12 @@ void V4L2Camera::requestComplete(Request *request)
> > >  }
> > >
> > >  int V4L2Camera::configure(StreamConfiguration *streamConfigOut,
> > > -                         const Size &size, const PixelFormat &pixelformat,
> > > -                         unsigned int bufferCount)
> > > +                         const Size &size, const PixelFormat &pixelformat)
> > >  {
> > >         StreamConfiguration &streamConfig = config_->at(0);
> > >         streamConfig.size.width = size.width;
> > >         streamConfig.size.height = size.height;
> > >         streamConfig.pixelFormat = pixelformat;
> > > -       streamConfig.bufferCount = bufferCount;
> > >         /* \todo memoryType (interval vs external) */
> > >
> > >         CameraConfiguration::Status validation = config_->validate();
> > > @@ -146,7 +146,6 @@ int V4L2Camera::validateConfiguration(const PixelFormat &pixelFormat,
> > >         StreamConfiguration &cfg = config->at(0);
> > >         cfg.size = size;
> > >         cfg.pixelFormat = pixelFormat;
> > > -       cfg.bufferCount = 1;
> > >
> > >         CameraConfiguration::Status validation = config->validate();
> > >         if (validation == CameraConfiguration::Invalid)
> > > @@ -299,3 +298,10 @@ bool V4L2Camera::isRunning()
> > >  {
> > >         return isRunning_;
> > >  }
> > > +
> > > +unsigned int V4L2Camera::minimumRequests(unsigned int count)
> > > +{
> > > +       unsigned int min = camera_->properties().get(properties::MinimumRequests);
> > > +
> > > +       return std::max(count, min);
> > > +}
> > > diff --git a/src/v4l2/v4l2_camera.h b/src/v4l2/v4l2_camera.h
> > > index a095f4e27524..4b5618ac12b5 100644
> > > --- a/src/v4l2/v4l2_camera.h
> > > +++ b/src/v4l2/v4l2_camera.h
> > > @@ -45,8 +45,7 @@ public:
> > >         std::vector<Buffer> completedBuffers();
> > >
> > >         int configure(StreamConfiguration *streamConfigOut,
> > > -                     const Size &size, const PixelFormat &pixelformat,
> > > -                     unsigned int bufferCount);
> > > +                     const Size &size, const PixelFormat &pixelformat);
> > >         int validateConfiguration(const PixelFormat &pixelformat,
> > >                                   const Size &size,
> > >                                   StreamConfiguration *streamConfigOut);
> > > @@ -65,6 +64,8 @@ public:
> > >
> > >         bool isRunning();
> > >
> > > +       unsigned int minimumRequests(unsigned int count);
> > > +
> > >  private:
> > >         void requestComplete(Request *request);
> > >
> > > diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
> > > index 7682c4bddf90..634ec84e0cbb 100644
> > > --- a/src/v4l2/v4l2_camera_proxy.cpp
> > > +++ b/src/v4l2/v4l2_camera_proxy.cpp
> > > @@ -349,8 +349,7 @@ int V4L2CameraProxy::vidioc_s_fmt(V4L2CameraFile *file, struct v4l2_format *arg)
> > >         Size size(arg->fmt.pix.width, arg->fmt.pix.height);
> > >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(arg->fmt.pix.pixelformat);
> > >         ret = vcam_->configure(&streamConfig_, size,
> > > -                              PixelFormatInfo::info(v4l2Format).format,
> > > -                              bufferCount_);
> > > +                              PixelFormatInfo::info(v4l2Format).format);
> > >         if (ret < 0)
> > >                 return -EINVAL;
> > >
> > > @@ -491,14 +490,13 @@ int V4L2CameraProxy::vidioc_reqbufs(V4L2CameraFile *file, struct v4l2_requestbuf
> > >         Size size(v4l2PixFormat_.width, v4l2PixFormat_.height);
> > >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(v4l2PixFormat_.pixelformat);
> > >         int ret = vcam_->configure(&streamConfig_, size,
> > > -                                  PixelFormatInfo::info(v4l2Format).format,
> > > -                                  arg->count);
> > > +                                  PixelFormatInfo::info(v4l2Format).format);
> > >         if (ret < 0)
> > >                 return -EINVAL;
> > >
> > >         setFmtFromConfig(streamConfig_);
> > >
> > > -       arg->count = streamConfig_.bufferCount;
> > > +       arg->count = vcam_->minimumRequests(arg->count);
> > >         bufferCount_ = arg->count;
> > >
> > >         ret = vcam_->allocBuffers(arg->count);
> > > diff --git a/test/camera/buffer_import.cpp b/test/camera/buffer_import.cpp
> > > index c504ea09e64b..67ac0ad20e15 100644
> > > --- a/test/camera/buffer_import.cpp
> > > +++ b/test/camera/buffer_import.cpp
> > > @@ -16,6 +16,8 @@
> > >  #include <libcamera/base/thread.h>
> > >  #include <libcamera/base/timer.h>
> > >
> > > +#include <libcamera/property_ids.h>
> > > +
> > >  #include "libcamera/internal/device_enumerator.h"
> > >  #include "libcamera/internal/media_device.h"
> > >  #include "libcamera/internal/v4l2_videodevice.h"
> > > @@ -92,10 +94,12 @@ protected:
> > >                         return TestFail;
> > >                 }
> > >
> > > +               unsigned int bufferCount = camera_->properties().get(properties::MinimumRequests);
> > > +
> > >                 Stream *stream = cfg.stream();
> > >
> > >                 BufferSource source;
> > > -               int ret = source.allocate(cfg);
> > > +               int ret = source.allocate(cfg, bufferCount);
> > >                 if (ret != TestPass)
> > >                         return ret;
> > >
> > > @@ -139,10 +143,10 @@ protected:
> > >                 while (timer.isRunning())
> > >                         dispatcher->processEvents();
> > >
> > > -               if (completeRequestsCount_ < cfg.bufferCount * 2) {
> > > +               if (completeRequestsCount_ < bufferCount * 2) {
> > >                         std::cout << "Failed to capture enough frames (got "
> > >                                   << completeRequestsCount_ << " expected at least "
> > > -                                 << cfg.bufferCount * 2 << ")" << std::endl;
> > > +                                 << bufferCount * 2 << ")" << std::endl;
> > >                         return TestFail;
> > >                 }
> > >
> > > diff --git a/test/libtest/buffer_source.cpp b/test/libtest/buffer_source.cpp
> > > index 73563f2fc39d..c3d5286a2462 100644
> > > --- a/test/libtest/buffer_source.cpp
> > > +++ b/test/libtest/buffer_source.cpp
> > > @@ -24,7 +24,7 @@ BufferSource::~BufferSource()
> > >                 media_->release();
> > >  }
> > >
> > > -int BufferSource::allocate(const StreamConfiguration &config)
> > > +int BufferSource::allocate(const StreamConfiguration &config, unsigned int count)
> > >  {
> > >         /* Locate and open the video device. */
> > >         std::string videoDeviceName = "vivid-000-vid-out";
> > > @@ -77,7 +77,7 @@ int BufferSource::allocate(const StreamConfiguration &config)
> > >                 return TestFail;
> > >         }
> > >
> > > -       if (video->allocateBuffers(config.bufferCount, &buffers_) < 0) {
> > > +       if (video->allocateBuffers(count, &buffers_) < 0) {
> > >                 std::cout << "Failed to allocate buffers" << std::endl;
> > >                 return TestFail;
> > >         }
> > > diff --git a/test/libtest/buffer_source.h b/test/libtest/buffer_source.h
> > > index 14b4770e8d8a..6a18e269a575 100644
> > > --- a/test/libtest/buffer_source.h
> > > +++ b/test/libtest/buffer_source.h
> > > @@ -20,7 +20,7 @@ public:
> > >         BufferSource();
> > >         ~BufferSource();
> > >
> > > -       int allocate(const StreamConfiguration &config);
> > > +       int allocate(const StreamConfiguration &config, unsigned int count);
> > >         const std::vector<std::unique_ptr<FrameBuffer>> &buffers();
> > >
> > >  private:
> > > diff --git a/test/v4l2_videodevice/buffer_cache.cpp b/test/v4l2_videodevice/buffer_cache.cpp
> > > index b3f2bec11783..07fddfd2617c 100644
> > > --- a/test/v4l2_videodevice/buffer_cache.cpp
> > > +++ b/test/v4l2_videodevice/buffer_cache.cpp
> > > @@ -10,6 +10,7 @@
> > >  #include <vector>
> > >
> > >  #include <libcamera/formats.h>
> > > +#include <libcamera/property_ids.h>
> > >  #include <libcamera/stream.h>
> > >
> > >  #include "buffer_source.h"
> > > @@ -145,10 +146,9 @@ public:
> > >                 StreamConfiguration cfg;
> > >                 cfg.pixelFormat = formats::YUYV;
> > >                 cfg.size = Size(600, 800);
> > > -               cfg.bufferCount = numBuffers;
> > >
> > >                 BufferSource source;
> > > -               int ret = source.allocate(cfg);
> > > +               int ret = source.allocate(cfg, numBuffers);
> > >                 if (ret != TestPass)
> > >                         return ret;
> > >
> > > --
> > > 2.32.0
> > >

Hi David,

On Fri, Jul 23, 2021 at 04:53:55PM +0100, David Plowman wrote:
> Hi Nicolas
> 
> Thanks for the explanations. I'm still not sure I entirely understand
> so perhaps a quick look at how I would have to change my application
> code might help? Here's what I have now (I've removed any
> "unimportant" bits!):
> 
> configuration_ = camera_->generateConfiguration({ StreamRole::StillCapture });
> configuration_->at(0).bufferCount = <value I have determined>;
> camera_->configure(configuration_.get());
> allocator_ = new FrameBufferAllocator(camera_);
> Stream *stream = configuration_->at(0).stream();
> allocator_->allocate(stream);
> // now allocator_->buffers(stream) has the buffers I want!
> 
> I guess one thing to note is that the bufferCount value varies with
> more than just the StreamRole, and I don't in general trust the
> pipeline handler to "know" what I want. Will this still be possible?

Oh I see... No, this won't be possible after we drop bufferCount. The
pipeline handler will decide for itself how many buffers to allocate internally,
possibly using the StreamRole as a hint.

I wasn't aware this could impact an application, since all the other pipeline
handlers actually ignore when bufferCount is set by the application, overriding
it when the configuration is validated. But now I'm noticing the raspberrypi
pipeline actually uses it.

Some context: This series actually began with me making
FrameBufferAllocator::allocate() receive a count argument instead of using the
value of bufferCount. But since Laurent mentioned that bufferCount was going
away eventually anyway I ended up removing it as well as part of this series.

I do understand how being able to specify a bufferCount value that suits your
specific usecase is useful, though... Laurent, what's your take on this? :)

Thanks,
Nícolas

> 
> Thanks!
> David
> 
> On Fri, 23 Jul 2021 at 14:10, Nícolas F. R. A. Prado
> <nfraprado@collabora.com> wrote:
> >
> > Hi David,
> >
> > On Fri, Jul 23, 2021 at 09:42:56AM +0100, David Plowman wrote:
> > > Hi Nicolas
> > >
> > > Thanks very much for all this work! I was wondering if I could ask a
> > > little more about this patch. In our applications, for example, we set
> > > the bufferCount according to the use-case that the application is
> > > implementing. For example:
> > >
> > > * For preview windows we set bufferCount to 4.
> > > * For video capture we drop fewer frames with a deeper queue so we set it to 6.
> > > * For stills capture we can get by with one frame, though use cases
> > > that capture several stills images for fusion work better if we set
> > > bufferCount to 2 or 3.
> > >
> > > I was wondering how our applications can achieve this behaviour if the
> > > bufferCount field is no longer available.
> >
> > Okay, so the short answer is that the applications, knowing their particular use
> > case, are responsible to provide enough requests to keep the pipeline going. On
> > the pipeline handler side, it's free to use how many internal buffers it wants.
> >
> > So in your case, the pipeline handler could still allocate that same number of
> > internal buffers as you previously did based on bufferCount, but now based
> > solely on the StreamRole set. The application would then allocate and queue
> > how many buffers fits the usage. (Note that before the application would call
> > FrameBufferAllocator::allocate() and it would allocate 'bufferCount' buffers,
> > but now the function takes a count argument so the application is free to choose
> > how many)
> >
> > Now, I guess it would be nice for the application to be able to query what is a
> > good number of buffers to use, for example 6 in the video capture of your use
> > case. At the moment, the only information available is that 1 is the minimum
> > number of buffers required. So the application would have to know that 6 is a
> > good number for video capture. Maybe another property could be introduced later
> > for this recommended amount, but previous discussions suggested this is very use
> > case dependent, so might not make sense.
> >
> > I hope this answers the question. If not, I'm still here :).
> >
> > Thanks,
> > Nícolas
> >
> > >
> > > Thanks!
> > > David
> > >
> > > On Fri, 23 Jul 2021 at 00:29, Nícolas F. R. A. Prado
> > > <nfraprado@collabora.com> wrote:
> > > >
> > > > Now that the number of buffers allocated by the FrameBufferAllocator
> > > > helper is passed through FrameBufferAllocator::allocate() and the
> > > > pipelines no longer use bufferCount for internal buffer or V4L2 buffer
> > > > slots allocation, we no longer need to have bufferCount in the
> > > > StreamConfiguration, so remove it.
> > > >
> > > > Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> > > > ---
> > > >
> > > > No changes in v7
> > > >
> > > > Changes in v6:
> > > > - Removed IPU3_BUFFER_COUNT as it was unused
> > > >
> > > >  include/libcamera/stream.h                         |  2 --
> > > >  src/android/camera_stream.cpp                      |  2 +-
> > > >  src/libcamera/pipeline/ipu3/cio2.cpp               |  1 -
> > > >  src/libcamera/pipeline/ipu3/ipu3.cpp               |  8 --------
> > > >  src/libcamera/pipeline/raspberrypi/raspberrypi.cpp |  6 ------
> > > >  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp      |  2 --
> > > >  src/libcamera/pipeline/simple/converter.cpp        |  3 ---
> > > >  src/libcamera/pipeline/simple/converter.h          |  3 ---
> > > >  src/libcamera/pipeline/simple/simple.cpp           |  5 +----
> > > >  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp       |  3 ---
> > > >  src/libcamera/pipeline/vimc/vimc.cpp               |  3 ---
> > > >  src/libcamera/stream.cpp                           |  9 ++-------
> > > >  src/v4l2/v4l2_camera.cpp                           | 14 ++++++++++----
> > > >  src/v4l2/v4l2_camera.h                             |  5 +++--
> > > >  src/v4l2/v4l2_camera_proxy.cpp                     |  8 +++-----
> > > >  test/camera/buffer_import.cpp                      | 10 +++++++---
> > > >  test/libtest/buffer_source.cpp                     |  4 ++--
> > > >  test/libtest/buffer_source.h                       |  2 +-
> > > >  test/v4l2_videodevice/buffer_cache.cpp             |  4 ++--
> > > >  19 files changed, 32 insertions(+), 62 deletions(-)
> > > >
> > > > diff --git a/include/libcamera/stream.h b/include/libcamera/stream.h
> > > > index 0c55e7164592..b25f0059f2f1 100644
> > > > --- a/include/libcamera/stream.h
> > > > +++ b/include/libcamera/stream.h
> > > > @@ -45,8 +45,6 @@ struct StreamConfiguration {
> > > >         unsigned int stride;
> > > >         unsigned int frameSize;
> > > >
> > > > -       unsigned int bufferCount;
> > > > -
> > > >         Stream *stream() const { return stream_; }
> > > >         void setStream(Stream *stream) { stream_ = stream; }
> > > >         const StreamFormats &formats() const { return formats_; }
> > > > diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
> > > > index b168e3c0c288..0794be409f82 100644
> > > > --- a/src/android/camera_stream.cpp
> > > > +++ b/src/android/camera_stream.cpp
> > > > @@ -94,7 +94,7 @@ int CameraStream::configure()
> > > >                         buffers_.push_back(frameBuffer.get());
> > > >         }
> > > >
> > > > -       camera3Stream_->max_buffers = configuration().bufferCount;
> > > > +       camera3Stream_->max_buffers = bufferCount;
> > > >
> > > >         return 0;
> > > >  }
> > > > diff --git a/src/libcamera/pipeline/ipu3/cio2.cpp b/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > index 1bcd580e251c..0e04e7214489 100644
> > > > --- a/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > +++ b/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > @@ -214,7 +214,6 @@ StreamConfiguration CIO2Device::generateConfiguration(Size size) const
> > > >
> > > >         cfg.size = sensorFormat.size;
> > > >         cfg.pixelFormat = mbusCodesToPixelFormat.at(sensorFormat.mbus_code);
> > > > -       cfg.bufferCount = CIO2_BUFFER_COUNT;
> > > >
> > > >         return cfg;
> > > >  }
> > > > diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > index 4efd201c05e5..b223b3f33cd0 100644
> > > > --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > @@ -38,7 +38,6 @@ namespace libcamera {
> > > >
> > > >  LOG_DEFINE_CATEGORY(IPU3)
> > > >
> > > > -static constexpr unsigned int IPU3_BUFFER_COUNT = 4;
> > > >  static constexpr unsigned int IPU3_MAX_STREAMS = 3;
> > > >  static const Size IMGU_OUTPUT_MIN_SIZE = { 2, 2 };
> > > >  static const Size IMGU_OUTPUT_MAX_SIZE = { 4480, 34004 };
> > > > @@ -295,7 +294,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > > >                         /* Initialize the RAW stream with the CIO2 configuration. */
> > > >                         cfg->size = cio2Configuration_.size;
> > > >                         cfg->pixelFormat = cio2Configuration_.pixelFormat;
> > > > -                       cfg->bufferCount = cio2Configuration_.bufferCount;
> > > >                         cfg->stride = info.stride(cfg->size.width, 0, 64);
> > > >                         cfg->frameSize = info.frameSize(cfg->size, 64);
> > > >                         cfg->setStream(const_cast<Stream *>(&data_->rawStream_));
> > > > @@ -339,7 +337,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > > >                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> > > >
> > > >                         cfg->pixelFormat = formats::NV12;
> > > > -                       cfg->bufferCount = IPU3_BUFFER_COUNT;
> > > >                         cfg->stride = info.stride(cfg->size.width, 0, 1);
> > > >                         cfg->frameSize = info.frameSize(cfg->size, 1);
> > > >
> > > > @@ -407,7 +404,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > >         Size sensorResolution = data->cio2_.sensor()->resolution();
> > > >         for (const StreamRole role : roles) {
> > > >                 std::map<PixelFormat, std::vector<SizeRange>> streamFormats;
> > > > -               unsigned int bufferCount;
> > > >                 PixelFormat pixelFormat;
> > > >                 Size size;
> > > >
> > > > @@ -428,7 +424,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > >                         size.height = utils::alignDown(size.height - 1,
> > > >                                                        IMGU_OUTPUT_HEIGHT_MARGIN);
> > > >                         pixelFormat = formats::NV12;
> > > > -                       bufferCount = IPU3_BUFFER_COUNT;
> > > >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> > > >
> > > >                         break;
> > > > @@ -438,7 +433,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > >                                 data->cio2_.generateConfiguration(sensorResolution);
> > > >                         pixelFormat = cio2Config.pixelFormat;
> > > >                         size = cio2Config.size;
> > > > -                       bufferCount = cio2Config.bufferCount;
> > > >
> > > >                         for (const PixelFormat &format : data->cio2_.formats())
> > > >                                 streamFormats[format] = data->cio2_.sizes();
> > > > @@ -457,7 +451,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > >                                                .alignedDownTo(IMGU_OUTPUT_WIDTH_ALIGN,
> > > >                                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> > > >                         pixelFormat = formats::NV12;
> > > > -                       bufferCount = IPU3_BUFFER_COUNT;
> > > >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> > > >
> > > >                         break;
> > > > @@ -474,7 +467,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > >                 StreamConfiguration cfg(formats);
> > > >                 cfg.size = size;
> > > >                 cfg.pixelFormat = pixelFormat;
> > > > -               cfg.bufferCount = bufferCount;
> > > >                 config->addConfiguration(cfg);
> > > >         }
> > > >
> > > > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > index 776e0f92aed1..e6fc0425c3ef 100644
> > > > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > @@ -473,7 +473,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > >         RPiCameraData *data = cameraData(camera);
> > > >         CameraConfiguration *config = new RPiCameraConfiguration(data);
> > > >         V4L2DeviceFormat sensorFormat;
> > > > -       unsigned int bufferCount;
> > > >         PixelFormat pixelFormat;
> > > >         V4L2VideoDevice::Formats fmts;
> > > >         Size size;
> > > > @@ -491,7 +490,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > >                         sensorFormat = findBestMode(fmts, size);
> > > >                         pixelFormat = sensorFormat.fourcc.toPixelFormat();
> > > >                         ASSERT(pixelFormat.isValid());
> > > > -                       bufferCount = 2;
> > > >                         rawCount++;
> > > >                         break;
> > > >
> > > > @@ -500,7 +498,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > >                         pixelFormat = formats::NV12;
> > > >                         /* Return the largest sensor resolution. */
> > > >                         size = data->sensor_->resolution();
> > > > -                       bufferCount = 1;
> > > >                         outCount++;
> > > >                         break;
> > > >
> > > > @@ -516,7 +513,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> > > >                         pixelFormat = formats::YUV420;
> > > >                         size = { 1920, 1080 };
> > > > -                       bufferCount = 4;
> > > >                         outCount++;
> > > >                         break;
> > > >
> > > > @@ -524,7 +520,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> > > >                         pixelFormat = formats::ARGB8888;
> > > >                         size = { 800, 600 };
> > > > -                       bufferCount = 4;
> > > >                         outCount++;
> > > >                         break;
> > > >
> > > > @@ -554,7 +549,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > >                 StreamConfiguration cfg(formats);
> > > >                 cfg.size = size;
> > > >                 cfg.pixelFormat = pixelFormat;
> > > > -               cfg.bufferCount = bufferCount;
> > > >                 config->addConfiguration(cfg);
> > > >         }
> > > >
> > > > diff --git a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > index fea330f72886..4961f3971e59 100644
> > > > --- a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > +++ b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > @@ -61,7 +61,6 @@ StreamConfiguration RkISP1Path::generateConfiguration(const Size &resolution)
> > > >         StreamConfiguration cfg(formats);
> > > >         cfg.pixelFormat = formats::NV12;
> > > >         cfg.size = maxResolution;
> > > > -       cfg.bufferCount = RKISP1_BUFFER_COUNT;
> > > >
> > > >         return cfg;
> > > >  }
> > > > @@ -77,7 +76,6 @@ CameraConfiguration::Status RkISP1Path::validate(StreamConfiguration *cfg)
> > > >
> > > >         cfg->size.boundTo(maxResolution_);
> > > >         cfg->size.expandTo(minResolution_);
> > > > -       cfg->bufferCount = RKISP1_BUFFER_COUNT;
> > > >
> > > >         V4L2DeviceFormat format;
> > > >         format.fourcc = video_->toV4L2PixelFormat(cfg->pixelFormat);
> > > > diff --git a/src/libcamera/pipeline/simple/converter.cpp b/src/libcamera/pipeline/simple/converter.cpp
> > > > index b3bcf01483f7..fda417793e80 100644
> > > > --- a/src/libcamera/pipeline/simple/converter.cpp
> > > > +++ b/src/libcamera/pipeline/simple/converter.cpp
> > > > @@ -89,9 +89,6 @@ int SimpleConverter::Stream::configure(const StreamConfiguration &inputCfg,
> > > >                 return -EINVAL;
> > > >         }
> > > >
> > > > -       inputBufferCount_ = inputCfg.bufferCount;
> > > > -       outputBufferCount_ = outputCfg.bufferCount;
> > > > -
> > > >         return 0;
> > > >  }
> > > >
> > > > diff --git a/src/libcamera/pipeline/simple/converter.h b/src/libcamera/pipeline/simple/converter.h
> > > > index 7e1d60674f62..406e63ca2a80 100644
> > > > --- a/src/libcamera/pipeline/simple/converter.h
> > > > +++ b/src/libcamera/pipeline/simple/converter.h
> > > > @@ -87,9 +87,6 @@ private:
> > > >                 SimpleConverter *converter_;
> > > >                 unsigned int index_;
> > > >                 std::unique_ptr<V4L2M2MDevice> m2m_;
> > > > -
> > > > -               unsigned int inputBufferCount_;
> > > > -               unsigned int outputBufferCount_;
> > > >         };
> > > >
> > > >         std::string deviceNode_;
> > > > diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> > > > index a1163eaf8be2..ded04914f610 100644
> > > > --- a/src/libcamera/pipeline/simple/simple.cpp
> > > > +++ b/src/libcamera/pipeline/simple/simple.cpp
> > > > @@ -628,7 +628,7 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> > > >                     cfg.size != pipeConfig_->captureSize)
> > > >                         needConversion_ = true;
> > > >
> > > > -               /* Set the stride, frameSize and bufferCount. */
> > > > +               /* Set the stride and frameSize. */
> > > >                 if (needConversion_) {
> > > >                         std::tie(cfg.stride, cfg.frameSize) =
> > > >                                 converter->strideAndFrameSize(cfg.pixelFormat, cfg.size);
> > > > @@ -646,8 +646,6 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> > > >                         cfg.stride = format.planes[0].bpl;
> > > >                         cfg.frameSize = format.planes[0].size;
> > > >                 }
> > > > -
> > > > -               cfg.bufferCount = 3;
> > > >         }
> > > >
> > > >         return status;
> > > > @@ -770,7 +768,6 @@ int SimplePipelineHandler::configure(Camera *camera, CameraConfiguration *c)
> > > >         inputCfg.pixelFormat = pipeConfig->captureFormat;
> > > >         inputCfg.size = pipeConfig->captureSize;
> > > >         inputCfg.stride = captureFormat.planes[0].bpl;
> > > > -       inputCfg.bufferCount = kNumInternalBuffers;
> > > >
> > > >         return converter_->configure(inputCfg, outputCfgs);
> > > >  }
> > > > diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > index 755949e7a59a..32482300f09a 100644
> > > > --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > @@ -150,8 +150,6 @@ CameraConfiguration::Status UVCCameraConfiguration::validate()
> > > >                 status = Adjusted;
> > > >         }
> > > >
> > > > -       cfg.bufferCount = 4;
> > > > -
> > > >         V4L2DeviceFormat format;
> > > >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> > > >         format.size = cfg.size;
> > > > @@ -193,7 +191,6 @@ CameraConfiguration *PipelineHandlerUVC::generateConfiguration(Camera *camera,
> > > >
> > > >         cfg.pixelFormat = formats.pixelformats().front();
> > > >         cfg.size = formats.sizes(cfg.pixelFormat).back();
> > > > -       cfg.bufferCount = 4;
> > > >
> > > >         config->addConfiguration(cfg);
> > > >
> > > > diff --git a/src/libcamera/pipeline/vimc/vimc.cpp b/src/libcamera/pipeline/vimc/vimc.cpp
> > > > index 24ba743a946c..a698427c4361 100644
> > > > --- a/src/libcamera/pipeline/vimc/vimc.cpp
> > > > +++ b/src/libcamera/pipeline/vimc/vimc.cpp
> > > > @@ -167,8 +167,6 @@ CameraConfiguration::Status VimcCameraConfiguration::validate()
> > > >                 status = Adjusted;
> > > >         }
> > > >
> > > > -       cfg.bufferCount = 4;
> > > > -
> > > >         V4L2DeviceFormat format;
> > > >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> > > >         format.size = cfg.size;
> > > > @@ -224,7 +222,6 @@ CameraConfiguration *PipelineHandlerVimc::generateConfiguration(Camera *camera,
> > > >
> > > >         cfg.pixelFormat = formats::BGR888;
> > > >         cfg.size = { 1920, 1080 };
> > > > -       cfg.bufferCount = 4;
> > > >
> > > >         config->addConfiguration(cfg);
> > > >
> > > > diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
> > > > index b8626775d224..ca507b72b26a 100644
> > > > --- a/src/libcamera/stream.cpp
> > > > +++ b/src/libcamera/stream.cpp
> > > > @@ -280,7 +280,7 @@ SizeRange StreamFormats::range(const PixelFormat &pixelformat) const
> > > >   * handlers provide StreamFormats.
> > > >   */
> > > >  StreamConfiguration::StreamConfiguration()
> > > > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > > > +       : pixelFormat(0), stride(0), frameSize(0),
> > > >           stream_(nullptr)
> > > >  {
> > > >  }
> > > > @@ -289,7 +289,7 @@ StreamConfiguration::StreamConfiguration()
> > > >   * \brief Construct a configuration with stream formats
> > > >   */
> > > >  StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > > > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > > > +       : pixelFormat(0), stride(0), frameSize(0),
> > > >           stream_(nullptr), formats_(formats)
> > > >  {
> > > >  }
> > > > @@ -324,11 +324,6 @@ StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > > >   * validating the configuration with a call to CameraConfiguration::validate().
> > > >   */
> > > >
> > > > -/**
> > > > - * \var StreamConfiguration::bufferCount
> > > > - * \brief Requested number of buffers to allocate for the stream
> > > > - */
> > > > -
> > > >  /**
> > > >   * \fn StreamConfiguration::stream()
> > > >   * \brief Retrieve the stream associated with the configuration
> > > > diff --git a/src/v4l2/v4l2_camera.cpp b/src/v4l2/v4l2_camera.cpp
> > > > index d01eacfa2b84..2ff9affc6388 100644
> > > > --- a/src/v4l2/v4l2_camera.cpp
> > > > +++ b/src/v4l2/v4l2_camera.cpp
> > > > @@ -12,6 +12,8 @@
> > > >
> > > >  #include <libcamera/base/log.h>
> > > >
> > > > +#include <libcamera/property_ids.h>
> > > > +
> > > >  using namespace libcamera;
> > > >
> > > >  LOG_DECLARE_CATEGORY(V4L2Compat)
> > > > @@ -107,14 +109,12 @@ void V4L2Camera::requestComplete(Request *request)
> > > >  }
> > > >
> > > >  int V4L2Camera::configure(StreamConfiguration *streamConfigOut,
> > > > -                         const Size &size, const PixelFormat &pixelformat,
> > > > -                         unsigned int bufferCount)
> > > > +                         const Size &size, const PixelFormat &pixelformat)
> > > >  {
> > > >         StreamConfiguration &streamConfig = config_->at(0);
> > > >         streamConfig.size.width = size.width;
> > > >         streamConfig.size.height = size.height;
> > > >         streamConfig.pixelFormat = pixelformat;
> > > > -       streamConfig.bufferCount = bufferCount;
> > > >         /* \todo memoryType (interval vs external) */
> > > >
> > > >         CameraConfiguration::Status validation = config_->validate();
> > > > @@ -146,7 +146,6 @@ int V4L2Camera::validateConfiguration(const PixelFormat &pixelFormat,
> > > >         StreamConfiguration &cfg = config->at(0);
> > > >         cfg.size = size;
> > > >         cfg.pixelFormat = pixelFormat;
> > > > -       cfg.bufferCount = 1;
> > > >
> > > >         CameraConfiguration::Status validation = config->validate();
> > > >         if (validation == CameraConfiguration::Invalid)
> > > > @@ -299,3 +298,10 @@ bool V4L2Camera::isRunning()
> > > >  {
> > > >         return isRunning_;
> > > >  }
> > > > +
> > > > +unsigned int V4L2Camera::minimumRequests(unsigned int count)
> > > > +{
> > > > +       unsigned int min = camera_->properties().get(properties::MinimumRequests);
> > > > +
> > > > +       return std::max(count, min);
> > > > +}
> > > > diff --git a/src/v4l2/v4l2_camera.h b/src/v4l2/v4l2_camera.h
> > > > index a095f4e27524..4b5618ac12b5 100644
> > > > --- a/src/v4l2/v4l2_camera.h
> > > > +++ b/src/v4l2/v4l2_camera.h
> > > > @@ -45,8 +45,7 @@ public:
> > > >         std::vector<Buffer> completedBuffers();
> > > >
> > > >         int configure(StreamConfiguration *streamConfigOut,
> > > > -                     const Size &size, const PixelFormat &pixelformat,
> > > > -                     unsigned int bufferCount);
> > > > +                     const Size &size, const PixelFormat &pixelformat);
> > > >         int validateConfiguration(const PixelFormat &pixelformat,
> > > >                                   const Size &size,
> > > >                                   StreamConfiguration *streamConfigOut);
> > > > @@ -65,6 +64,8 @@ public:
> > > >
> > > >         bool isRunning();
> > > >
> > > > +       unsigned int minimumRequests(unsigned int count);
> > > > +
> > > >  private:
> > > >         void requestComplete(Request *request);
> > > >
> > > > diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
> > > > index 7682c4bddf90..634ec84e0cbb 100644
> > > > --- a/src/v4l2/v4l2_camera_proxy.cpp
> > > > +++ b/src/v4l2/v4l2_camera_proxy.cpp
> > > > @@ -349,8 +349,7 @@ int V4L2CameraProxy::vidioc_s_fmt(V4L2CameraFile *file, struct v4l2_format *arg)
> > > >         Size size(arg->fmt.pix.width, arg->fmt.pix.height);
> > > >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(arg->fmt.pix.pixelformat);
> > > >         ret = vcam_->configure(&streamConfig_, size,
> > > > -                              PixelFormatInfo::info(v4l2Format).format,
> > > > -                              bufferCount_);
> > > > +                              PixelFormatInfo::info(v4l2Format).format);
> > > >         if (ret < 0)
> > > >                 return -EINVAL;
> > > >
> > > > @@ -491,14 +490,13 @@ int V4L2CameraProxy::vidioc_reqbufs(V4L2CameraFile *file, struct v4l2_requestbuf
> > > >         Size size(v4l2PixFormat_.width, v4l2PixFormat_.height);
> > > >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(v4l2PixFormat_.pixelformat);
> > > >         int ret = vcam_->configure(&streamConfig_, size,
> > > > -                                  PixelFormatInfo::info(v4l2Format).format,
> > > > -                                  arg->count);
> > > > +                                  PixelFormatInfo::info(v4l2Format).format);
> > > >         if (ret < 0)
> > > >                 return -EINVAL;
> > > >
> > > >         setFmtFromConfig(streamConfig_);
> > > >
> > > > -       arg->count = streamConfig_.bufferCount;
> > > > +       arg->count = vcam_->minimumRequests(arg->count);
> > > >         bufferCount_ = arg->count;
> > > >
> > > >         ret = vcam_->allocBuffers(arg->count);
> > > > diff --git a/test/camera/buffer_import.cpp b/test/camera/buffer_import.cpp
> > > > index c504ea09e64b..67ac0ad20e15 100644
> > > > --- a/test/camera/buffer_import.cpp
> > > > +++ b/test/camera/buffer_import.cpp
> > > > @@ -16,6 +16,8 @@
> > > >  #include <libcamera/base/thread.h>
> > > >  #include <libcamera/base/timer.h>
> > > >
> > > > +#include <libcamera/property_ids.h>
> > > > +
> > > >  #include "libcamera/internal/device_enumerator.h"
> > > >  #include "libcamera/internal/media_device.h"
> > > >  #include "libcamera/internal/v4l2_videodevice.h"
> > > > @@ -92,10 +94,12 @@ protected:
> > > >                         return TestFail;
> > > >                 }
> > > >
> > > > +               unsigned int bufferCount = camera_->properties().get(properties::MinimumRequests);
> > > > +
> > > >                 Stream *stream = cfg.stream();
> > > >
> > > >                 BufferSource source;
> > > > -               int ret = source.allocate(cfg);
> > > > +               int ret = source.allocate(cfg, bufferCount);
> > > >                 if (ret != TestPass)
> > > >                         return ret;
> > > >
> > > > @@ -139,10 +143,10 @@ protected:
> > > >                 while (timer.isRunning())
> > > >                         dispatcher->processEvents();
> > > >
> > > > -               if (completeRequestsCount_ < cfg.bufferCount * 2) {
> > > > +               if (completeRequestsCount_ < bufferCount * 2) {
> > > >                         std::cout << "Failed to capture enough frames (got "
> > > >                                   << completeRequestsCount_ << " expected at least "
> > > > -                                 << cfg.bufferCount * 2 << ")" << std::endl;
> > > > +                                 << bufferCount * 2 << ")" << std::endl;
> > > >                         return TestFail;
> > > >                 }
> > > >
> > > > diff --git a/test/libtest/buffer_source.cpp b/test/libtest/buffer_source.cpp
> > > > index 73563f2fc39d..c3d5286a2462 100644
> > > > --- a/test/libtest/buffer_source.cpp
> > > > +++ b/test/libtest/buffer_source.cpp
> > > > @@ -24,7 +24,7 @@ BufferSource::~BufferSource()
> > > >                 media_->release();
> > > >  }
> > > >
> > > > -int BufferSource::allocate(const StreamConfiguration &config)
> > > > +int BufferSource::allocate(const StreamConfiguration &config, unsigned int count)
> > > >  {
> > > >         /* Locate and open the video device. */
> > > >         std::string videoDeviceName = "vivid-000-vid-out";
> > > > @@ -77,7 +77,7 @@ int BufferSource::allocate(const StreamConfiguration &config)
> > > >                 return TestFail;
> > > >         }
> > > >
> > > > -       if (video->allocateBuffers(config.bufferCount, &buffers_) < 0) {
> > > > +       if (video->allocateBuffers(count, &buffers_) < 0) {
> > > >                 std::cout << "Failed to allocate buffers" << std::endl;
> > > >                 return TestFail;
> > > >         }
> > > > diff --git a/test/libtest/buffer_source.h b/test/libtest/buffer_source.h
> > > > index 14b4770e8d8a..6a18e269a575 100644
> > > > --- a/test/libtest/buffer_source.h
> > > > +++ b/test/libtest/buffer_source.h
> > > > @@ -20,7 +20,7 @@ public:
> > > >         BufferSource();
> > > >         ~BufferSource();
> > > >
> > > > -       int allocate(const StreamConfiguration &config);
> > > > +       int allocate(const StreamConfiguration &config, unsigned int count);
> > > >         const std::vector<std::unique_ptr<FrameBuffer>> &buffers();
> > > >
> > > >  private:
> > > > diff --git a/test/v4l2_videodevice/buffer_cache.cpp b/test/v4l2_videodevice/buffer_cache.cpp
> > > > index b3f2bec11783..07fddfd2617c 100644
> > > > --- a/test/v4l2_videodevice/buffer_cache.cpp
> > > > +++ b/test/v4l2_videodevice/buffer_cache.cpp
> > > > @@ -10,6 +10,7 @@
> > > >  #include <vector>
> > > >
> > > >  #include <libcamera/formats.h>
> > > > +#include <libcamera/property_ids.h>
> > > >  #include <libcamera/stream.h>
> > > >
> > > >  #include "buffer_source.h"
> > > > @@ -145,10 +146,9 @@ public:
> > > >                 StreamConfiguration cfg;
> > > >                 cfg.pixelFormat = formats::YUYV;
> > > >                 cfg.size = Size(600, 800);
> > > > -               cfg.bufferCount = numBuffers;
> > > >
> > > >                 BufferSource source;
> > > > -               int ret = source.allocate(cfg);
> > > > +               int ret = source.allocate(cfg, numBuffers);
> > > >                 if (ret != TestPass)
> > > >                         return ret;
> > > >
> > > > --
> > > > 2.32.0
> > > >

Hi again

I thought that perhaps I could explain in more detail why I think
applications need to be able to set (or influence) the buffer count
and not leave it to the pipeline handler. My use-case is as follows.

I'm running some standard sort of application such as video recording
for which there are maybe 4 buffers allocated. Now, I also want to do
some image analysis that perhaps causes me to change something about
the recording (maybe change camera settings, or even stop the
recording). But this image analysis task is relatively slow.

One option is to copy the camera frames so that I can return the
buffers in the request back to the camera. But copying images is
generally undesirable. Instead I'd prefer to hold on to the buffer
only now my camera pipeline is effectively working with only 3
buffers, which is not enough. When I eventually finish with the buffer
I will return it, and then grab the next one to keep again!

So at the very least, the application needs to be able to say "please
allocate <n> more buffers than you thought you needed". Does that make
sense? Will this be possible in the new scheme?

Thanks!
David

On Fri, 23 Jul 2021 at 22:08, Nícolas F. R. A. Prado
<nfraprado@collabora.com> wrote:
>
> Hi David,
>
> On Fri, Jul 23, 2021 at 04:53:55PM +0100, David Plowman wrote:
> > Hi Nicolas
> >
> > Thanks for the explanations. I'm still not sure I entirely understand
> > so perhaps a quick look at how I would have to change my application
> > code might help? Here's what I have now (I've removed any
> > "unimportant" bits!):
> >
> > configuration_ = camera_->generateConfiguration({ StreamRole::StillCapture });
> > configuration_->at(0).bufferCount = <value I have determined>;
> > camera_->configure(configuration_.get());
> > allocator_ = new FrameBufferAllocator(camera_);
> > Stream *stream = configuration_->at(0).stream();
> > allocator_->allocate(stream);
> > // now allocator_->buffers(stream) has the buffers I want!
> >
> > I guess one thing to note is that the bufferCount value varies with
> > more than just the StreamRole, and I don't in general trust the
> > pipeline handler to "know" what I want. Will this still be possible?
>
> Oh I see... No, this won't be possible after we drop bufferCount. The
> pipeline handler will decide for itself how many buffers to allocate internally,
> possibly using the StreamRole as a hint.
>
> I wasn't aware this could impact an application, since all the other pipeline
> handlers actually ignore when bufferCount is set by the application, overriding
> it when the configuration is validated. But now I'm noticing the raspberrypi
> pipeline actually uses it.
>
> Some context: This series actually began with me making
> FrameBufferAllocator::allocate() receive a count argument instead of using the
> value of bufferCount. But since Laurent mentioned that bufferCount was going
> away eventually anyway I ended up removing it as well as part of this series.
>
> I do understand how being able to specify a bufferCount value that suits your
> specific usecase is useful, though... Laurent, what's your take on this? :)
>
> Thanks,
> Nícolas
>
> >
> > Thanks!
> > David
> >
> > On Fri, 23 Jul 2021 at 14:10, Nícolas F. R. A. Prado
> > <nfraprado@collabora.com> wrote:
> > >
> > > Hi David,
> > >
> > > On Fri, Jul 23, 2021 at 09:42:56AM +0100, David Plowman wrote:
> > > > Hi Nicolas
> > > >
> > > > Thanks very much for all this work! I was wondering if I could ask a
> > > > little more about this patch. In our applications, for example, we set
> > > > the bufferCount according to the use-case that the application is
> > > > implementing. For example:
> > > >
> > > > * For preview windows we set bufferCount to 4.
> > > > * For video capture we drop fewer frames with a deeper queue so we set it to 6.
> > > > * For stills capture we can get by with one frame, though use cases
> > > > that capture several stills images for fusion work better if we set
> > > > bufferCount to 2 or 3.
> > > >
> > > > I was wondering how our applications can achieve this behaviour if the
> > > > bufferCount field is no longer available.
> > >
> > > Okay, so the short answer is that the applications, knowing their particular use
> > > case, are responsible to provide enough requests to keep the pipeline going. On
> > > the pipeline handler side, it's free to use how many internal buffers it wants.
> > >
> > > So in your case, the pipeline handler could still allocate that same number of
> > > internal buffers as you previously did based on bufferCount, but now based
> > > solely on the StreamRole set. The application would then allocate and queue
> > > how many buffers fits the usage. (Note that before the application would call
> > > FrameBufferAllocator::allocate() and it would allocate 'bufferCount' buffers,
> > > but now the function takes a count argument so the application is free to choose
> > > how many)
> > >
> > > Now, I guess it would be nice for the application to be able to query what is a
> > > good number of buffers to use, for example 6 in the video capture of your use
> > > case. At the moment, the only information available is that 1 is the minimum
> > > number of buffers required. So the application would have to know that 6 is a
> > > good number for video capture. Maybe another property could be introduced later
> > > for this recommended amount, but previous discussions suggested this is very use
> > > case dependent, so might not make sense.
> > >
> > > I hope this answers the question. If not, I'm still here :).
> > >
> > > Thanks,
> > > Nícolas
> > >
> > > >
> > > > Thanks!
> > > > David
> > > >
> > > > On Fri, 23 Jul 2021 at 00:29, Nícolas F. R. A. Prado
> > > > <nfraprado@collabora.com> wrote:
> > > > >
> > > > > Now that the number of buffers allocated by the FrameBufferAllocator
> > > > > helper is passed through FrameBufferAllocator::allocate() and the
> > > > > pipelines no longer use bufferCount for internal buffer or V4L2 buffer
> > > > > slots allocation, we no longer need to have bufferCount in the
> > > > > StreamConfiguration, so remove it.
> > > > >
> > > > > Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> > > > > ---
> > > > >
> > > > > No changes in v7
> > > > >
> > > > > Changes in v6:
> > > > > - Removed IPU3_BUFFER_COUNT as it was unused
> > > > >
> > > > >  include/libcamera/stream.h                         |  2 --
> > > > >  src/android/camera_stream.cpp                      |  2 +-
> > > > >  src/libcamera/pipeline/ipu3/cio2.cpp               |  1 -
> > > > >  src/libcamera/pipeline/ipu3/ipu3.cpp               |  8 --------
> > > > >  src/libcamera/pipeline/raspberrypi/raspberrypi.cpp |  6 ------
> > > > >  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp      |  2 --
> > > > >  src/libcamera/pipeline/simple/converter.cpp        |  3 ---
> > > > >  src/libcamera/pipeline/simple/converter.h          |  3 ---
> > > > >  src/libcamera/pipeline/simple/simple.cpp           |  5 +----
> > > > >  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp       |  3 ---
> > > > >  src/libcamera/pipeline/vimc/vimc.cpp               |  3 ---
> > > > >  src/libcamera/stream.cpp                           |  9 ++-------
> > > > >  src/v4l2/v4l2_camera.cpp                           | 14 ++++++++++----
> > > > >  src/v4l2/v4l2_camera.h                             |  5 +++--
> > > > >  src/v4l2/v4l2_camera_proxy.cpp                     |  8 +++-----
> > > > >  test/camera/buffer_import.cpp                      | 10 +++++++---
> > > > >  test/libtest/buffer_source.cpp                     |  4 ++--
> > > > >  test/libtest/buffer_source.h                       |  2 +-
> > > > >  test/v4l2_videodevice/buffer_cache.cpp             |  4 ++--
> > > > >  19 files changed, 32 insertions(+), 62 deletions(-)
> > > > >
> > > > > diff --git a/include/libcamera/stream.h b/include/libcamera/stream.h
> > > > > index 0c55e7164592..b25f0059f2f1 100644
> > > > > --- a/include/libcamera/stream.h
> > > > > +++ b/include/libcamera/stream.h
> > > > > @@ -45,8 +45,6 @@ struct StreamConfiguration {
> > > > >         unsigned int stride;
> > > > >         unsigned int frameSize;
> > > > >
> > > > > -       unsigned int bufferCount;
> > > > > -
> > > > >         Stream *stream() const { return stream_; }
> > > > >         void setStream(Stream *stream) { stream_ = stream; }
> > > > >         const StreamFormats &formats() const { return formats_; }
> > > > > diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
> > > > > index b168e3c0c288..0794be409f82 100644
> > > > > --- a/src/android/camera_stream.cpp
> > > > > +++ b/src/android/camera_stream.cpp
> > > > > @@ -94,7 +94,7 @@ int CameraStream::configure()
> > > > >                         buffers_.push_back(frameBuffer.get());
> > > > >         }
> > > > >
> > > > > -       camera3Stream_->max_buffers = configuration().bufferCount;
> > > > > +       camera3Stream_->max_buffers = bufferCount;
> > > > >
> > > > >         return 0;
> > > > >  }
> > > > > diff --git a/src/libcamera/pipeline/ipu3/cio2.cpp b/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > > index 1bcd580e251c..0e04e7214489 100644
> > > > > --- a/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > > +++ b/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > > @@ -214,7 +214,6 @@ StreamConfiguration CIO2Device::generateConfiguration(Size size) const
> > > > >
> > > > >         cfg.size = sensorFormat.size;
> > > > >         cfg.pixelFormat = mbusCodesToPixelFormat.at(sensorFormat.mbus_code);
> > > > > -       cfg.bufferCount = CIO2_BUFFER_COUNT;
> > > > >
> > > > >         return cfg;
> > > > >  }
> > > > > diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > index 4efd201c05e5..b223b3f33cd0 100644
> > > > > --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > @@ -38,7 +38,6 @@ namespace libcamera {
> > > > >
> > > > >  LOG_DEFINE_CATEGORY(IPU3)
> > > > >
> > > > > -static constexpr unsigned int IPU3_BUFFER_COUNT = 4;
> > > > >  static constexpr unsigned int IPU3_MAX_STREAMS = 3;
> > > > >  static const Size IMGU_OUTPUT_MIN_SIZE = { 2, 2 };
> > > > >  static const Size IMGU_OUTPUT_MAX_SIZE = { 4480, 34004 };
> > > > > @@ -295,7 +294,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > > > >                         /* Initialize the RAW stream with the CIO2 configuration. */
> > > > >                         cfg->size = cio2Configuration_.size;
> > > > >                         cfg->pixelFormat = cio2Configuration_.pixelFormat;
> > > > > -                       cfg->bufferCount = cio2Configuration_.bufferCount;
> > > > >                         cfg->stride = info.stride(cfg->size.width, 0, 64);
> > > > >                         cfg->frameSize = info.frameSize(cfg->size, 64);
> > > > >                         cfg->setStream(const_cast<Stream *>(&data_->rawStream_));
> > > > > @@ -339,7 +337,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > > > >                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> > > > >
> > > > >                         cfg->pixelFormat = formats::NV12;
> > > > > -                       cfg->bufferCount = IPU3_BUFFER_COUNT;
> > > > >                         cfg->stride = info.stride(cfg->size.width, 0, 1);
> > > > >                         cfg->frameSize = info.frameSize(cfg->size, 1);
> > > > >
> > > > > @@ -407,7 +404,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > >         Size sensorResolution = data->cio2_.sensor()->resolution();
> > > > >         for (const StreamRole role : roles) {
> > > > >                 std::map<PixelFormat, std::vector<SizeRange>> streamFormats;
> > > > > -               unsigned int bufferCount;
> > > > >                 PixelFormat pixelFormat;
> > > > >                 Size size;
> > > > >
> > > > > @@ -428,7 +424,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > >                         size.height = utils::alignDown(size.height - 1,
> > > > >                                                        IMGU_OUTPUT_HEIGHT_MARGIN);
> > > > >                         pixelFormat = formats::NV12;
> > > > > -                       bufferCount = IPU3_BUFFER_COUNT;
> > > > >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> > > > >
> > > > >                         break;
> > > > > @@ -438,7 +433,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > >                                 data->cio2_.generateConfiguration(sensorResolution);
> > > > >                         pixelFormat = cio2Config.pixelFormat;
> > > > >                         size = cio2Config.size;
> > > > > -                       bufferCount = cio2Config.bufferCount;
> > > > >
> > > > >                         for (const PixelFormat &format : data->cio2_.formats())
> > > > >                                 streamFormats[format] = data->cio2_.sizes();
> > > > > @@ -457,7 +451,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > >                                                .alignedDownTo(IMGU_OUTPUT_WIDTH_ALIGN,
> > > > >                                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> > > > >                         pixelFormat = formats::NV12;
> > > > > -                       bufferCount = IPU3_BUFFER_COUNT;
> > > > >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> > > > >
> > > > >                         break;
> > > > > @@ -474,7 +467,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > >                 StreamConfiguration cfg(formats);
> > > > >                 cfg.size = size;
> > > > >                 cfg.pixelFormat = pixelFormat;
> > > > > -               cfg.bufferCount = bufferCount;
> > > > >                 config->addConfiguration(cfg);
> > > > >         }
> > > > >
> > > > > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > index 776e0f92aed1..e6fc0425c3ef 100644
> > > > > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > @@ -473,7 +473,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > >         RPiCameraData *data = cameraData(camera);
> > > > >         CameraConfiguration *config = new RPiCameraConfiguration(data);
> > > > >         V4L2DeviceFormat sensorFormat;
> > > > > -       unsigned int bufferCount;
> > > > >         PixelFormat pixelFormat;
> > > > >         V4L2VideoDevice::Formats fmts;
> > > > >         Size size;
> > > > > @@ -491,7 +490,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > >                         sensorFormat = findBestMode(fmts, size);
> > > > >                         pixelFormat = sensorFormat.fourcc.toPixelFormat();
> > > > >                         ASSERT(pixelFormat.isValid());
> > > > > -                       bufferCount = 2;
> > > > >                         rawCount++;
> > > > >                         break;
> > > > >
> > > > > @@ -500,7 +498,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > >                         pixelFormat = formats::NV12;
> > > > >                         /* Return the largest sensor resolution. */
> > > > >                         size = data->sensor_->resolution();
> > > > > -                       bufferCount = 1;
> > > > >                         outCount++;
> > > > >                         break;
> > > > >
> > > > > @@ -516,7 +513,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> > > > >                         pixelFormat = formats::YUV420;
> > > > >                         size = { 1920, 1080 };
> > > > > -                       bufferCount = 4;
> > > > >                         outCount++;
> > > > >                         break;
> > > > >
> > > > > @@ -524,7 +520,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> > > > >                         pixelFormat = formats::ARGB8888;
> > > > >                         size = { 800, 600 };
> > > > > -                       bufferCount = 4;
> > > > >                         outCount++;
> > > > >                         break;
> > > > >
> > > > > @@ -554,7 +549,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > >                 StreamConfiguration cfg(formats);
> > > > >                 cfg.size = size;
> > > > >                 cfg.pixelFormat = pixelFormat;
> > > > > -               cfg.bufferCount = bufferCount;
> > > > >                 config->addConfiguration(cfg);
> > > > >         }
> > > > >
> > > > > diff --git a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > > index fea330f72886..4961f3971e59 100644
> > > > > --- a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > > +++ b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > > @@ -61,7 +61,6 @@ StreamConfiguration RkISP1Path::generateConfiguration(const Size &resolution)
> > > > >         StreamConfiguration cfg(formats);
> > > > >         cfg.pixelFormat = formats::NV12;
> > > > >         cfg.size = maxResolution;
> > > > > -       cfg.bufferCount = RKISP1_BUFFER_COUNT;
> > > > >
> > > > >         return cfg;
> > > > >  }
> > > > > @@ -77,7 +76,6 @@ CameraConfiguration::Status RkISP1Path::validate(StreamConfiguration *cfg)
> > > > >
> > > > >         cfg->size.boundTo(maxResolution_);
> > > > >         cfg->size.expandTo(minResolution_);
> > > > > -       cfg->bufferCount = RKISP1_BUFFER_COUNT;
> > > > >
> > > > >         V4L2DeviceFormat format;
> > > > >         format.fourcc = video_->toV4L2PixelFormat(cfg->pixelFormat);
> > > > > diff --git a/src/libcamera/pipeline/simple/converter.cpp b/src/libcamera/pipeline/simple/converter.cpp
> > > > > index b3bcf01483f7..fda417793e80 100644
> > > > > --- a/src/libcamera/pipeline/simple/converter.cpp
> > > > > +++ b/src/libcamera/pipeline/simple/converter.cpp
> > > > > @@ -89,9 +89,6 @@ int SimpleConverter::Stream::configure(const StreamConfiguration &inputCfg,
> > > > >                 return -EINVAL;
> > > > >         }
> > > > >
> > > > > -       inputBufferCount_ = inputCfg.bufferCount;
> > > > > -       outputBufferCount_ = outputCfg.bufferCount;
> > > > > -
> > > > >         return 0;
> > > > >  }
> > > > >
> > > > > diff --git a/src/libcamera/pipeline/simple/converter.h b/src/libcamera/pipeline/simple/converter.h
> > > > > index 7e1d60674f62..406e63ca2a80 100644
> > > > > --- a/src/libcamera/pipeline/simple/converter.h
> > > > > +++ b/src/libcamera/pipeline/simple/converter.h
> > > > > @@ -87,9 +87,6 @@ private:
> > > > >                 SimpleConverter *converter_;
> > > > >                 unsigned int index_;
> > > > >                 std::unique_ptr<V4L2M2MDevice> m2m_;
> > > > > -
> > > > > -               unsigned int inputBufferCount_;
> > > > > -               unsigned int outputBufferCount_;
> > > > >         };
> > > > >
> > > > >         std::string deviceNode_;
> > > > > diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> > > > > index a1163eaf8be2..ded04914f610 100644
> > > > > --- a/src/libcamera/pipeline/simple/simple.cpp
> > > > > +++ b/src/libcamera/pipeline/simple/simple.cpp
> > > > > @@ -628,7 +628,7 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> > > > >                     cfg.size != pipeConfig_->captureSize)
> > > > >                         needConversion_ = true;
> > > > >
> > > > > -               /* Set the stride, frameSize and bufferCount. */
> > > > > +               /* Set the stride and frameSize. */
> > > > >                 if (needConversion_) {
> > > > >                         std::tie(cfg.stride, cfg.frameSize) =
> > > > >                                 converter->strideAndFrameSize(cfg.pixelFormat, cfg.size);
> > > > > @@ -646,8 +646,6 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> > > > >                         cfg.stride = format.planes[0].bpl;
> > > > >                         cfg.frameSize = format.planes[0].size;
> > > > >                 }
> > > > > -
> > > > > -               cfg.bufferCount = 3;
> > > > >         }
> > > > >
> > > > >         return status;
> > > > > @@ -770,7 +768,6 @@ int SimplePipelineHandler::configure(Camera *camera, CameraConfiguration *c)
> > > > >         inputCfg.pixelFormat = pipeConfig->captureFormat;
> > > > >         inputCfg.size = pipeConfig->captureSize;
> > > > >         inputCfg.stride = captureFormat.planes[0].bpl;
> > > > > -       inputCfg.bufferCount = kNumInternalBuffers;
> > > > >
> > > > >         return converter_->configure(inputCfg, outputCfgs);
> > > > >  }
> > > > > diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > > index 755949e7a59a..32482300f09a 100644
> > > > > --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > > +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > > @@ -150,8 +150,6 @@ CameraConfiguration::Status UVCCameraConfiguration::validate()
> > > > >                 status = Adjusted;
> > > > >         }
> > > > >
> > > > > -       cfg.bufferCount = 4;
> > > > > -
> > > > >         V4L2DeviceFormat format;
> > > > >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> > > > >         format.size = cfg.size;
> > > > > @@ -193,7 +191,6 @@ CameraConfiguration *PipelineHandlerUVC::generateConfiguration(Camera *camera,
> > > > >
> > > > >         cfg.pixelFormat = formats.pixelformats().front();
> > > > >         cfg.size = formats.sizes(cfg.pixelFormat).back();
> > > > > -       cfg.bufferCount = 4;
> > > > >
> > > > >         config->addConfiguration(cfg);
> > > > >
> > > > > diff --git a/src/libcamera/pipeline/vimc/vimc.cpp b/src/libcamera/pipeline/vimc/vimc.cpp
> > > > > index 24ba743a946c..a698427c4361 100644
> > > > > --- a/src/libcamera/pipeline/vimc/vimc.cpp
> > > > > +++ b/src/libcamera/pipeline/vimc/vimc.cpp
> > > > > @@ -167,8 +167,6 @@ CameraConfiguration::Status VimcCameraConfiguration::validate()
> > > > >                 status = Adjusted;
> > > > >         }
> > > > >
> > > > > -       cfg.bufferCount = 4;
> > > > > -
> > > > >         V4L2DeviceFormat format;
> > > > >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> > > > >         format.size = cfg.size;
> > > > > @@ -224,7 +222,6 @@ CameraConfiguration *PipelineHandlerVimc::generateConfiguration(Camera *camera,
> > > > >
> > > > >         cfg.pixelFormat = formats::BGR888;
> > > > >         cfg.size = { 1920, 1080 };
> > > > > -       cfg.bufferCount = 4;
> > > > >
> > > > >         config->addConfiguration(cfg);
> > > > >
> > > > > diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
> > > > > index b8626775d224..ca507b72b26a 100644
> > > > > --- a/src/libcamera/stream.cpp
> > > > > +++ b/src/libcamera/stream.cpp
> > > > > @@ -280,7 +280,7 @@ SizeRange StreamFormats::range(const PixelFormat &pixelformat) const
> > > > >   * handlers provide StreamFormats.
> > > > >   */
> > > > >  StreamConfiguration::StreamConfiguration()
> > > > > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > > > > +       : pixelFormat(0), stride(0), frameSize(0),
> > > > >           stream_(nullptr)
> > > > >  {
> > > > >  }
> > > > > @@ -289,7 +289,7 @@ StreamConfiguration::StreamConfiguration()
> > > > >   * \brief Construct a configuration with stream formats
> > > > >   */
> > > > >  StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > > > > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > > > > +       : pixelFormat(0), stride(0), frameSize(0),
> > > > >           stream_(nullptr), formats_(formats)
> > > > >  {
> > > > >  }
> > > > > @@ -324,11 +324,6 @@ StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > > > >   * validating the configuration with a call to CameraConfiguration::validate().
> > > > >   */
> > > > >
> > > > > -/**
> > > > > - * \var StreamConfiguration::bufferCount
> > > > > - * \brief Requested number of buffers to allocate for the stream
> > > > > - */
> > > > > -
> > > > >  /**
> > > > >   * \fn StreamConfiguration::stream()
> > > > >   * \brief Retrieve the stream associated with the configuration
> > > > > diff --git a/src/v4l2/v4l2_camera.cpp b/src/v4l2/v4l2_camera.cpp
> > > > > index d01eacfa2b84..2ff9affc6388 100644
> > > > > --- a/src/v4l2/v4l2_camera.cpp
> > > > > +++ b/src/v4l2/v4l2_camera.cpp
> > > > > @@ -12,6 +12,8 @@
> > > > >
> > > > >  #include <libcamera/base/log.h>
> > > > >
> > > > > +#include <libcamera/property_ids.h>
> > > > > +
> > > > >  using namespace libcamera;
> > > > >
> > > > >  LOG_DECLARE_CATEGORY(V4L2Compat)
> > > > > @@ -107,14 +109,12 @@ void V4L2Camera::requestComplete(Request *request)
> > > > >  }
> > > > >
> > > > >  int V4L2Camera::configure(StreamConfiguration *streamConfigOut,
> > > > > -                         const Size &size, const PixelFormat &pixelformat,
> > > > > -                         unsigned int bufferCount)
> > > > > +                         const Size &size, const PixelFormat &pixelformat)
> > > > >  {
> > > > >         StreamConfiguration &streamConfig = config_->at(0);
> > > > >         streamConfig.size.width = size.width;
> > > > >         streamConfig.size.height = size.height;
> > > > >         streamConfig.pixelFormat = pixelformat;
> > > > > -       streamConfig.bufferCount = bufferCount;
> > > > >         /* \todo memoryType (interval vs external) */
> > > > >
> > > > >         CameraConfiguration::Status validation = config_->validate();
> > > > > @@ -146,7 +146,6 @@ int V4L2Camera::validateConfiguration(const PixelFormat &pixelFormat,
> > > > >         StreamConfiguration &cfg = config->at(0);
> > > > >         cfg.size = size;
> > > > >         cfg.pixelFormat = pixelFormat;
> > > > > -       cfg.bufferCount = 1;
> > > > >
> > > > >         CameraConfiguration::Status validation = config->validate();
> > > > >         if (validation == CameraConfiguration::Invalid)
> > > > > @@ -299,3 +298,10 @@ bool V4L2Camera::isRunning()
> > > > >  {
> > > > >         return isRunning_;
> > > > >  }
> > > > > +
> > > > > +unsigned int V4L2Camera::minimumRequests(unsigned int count)
> > > > > +{
> > > > > +       unsigned int min = camera_->properties().get(properties::MinimumRequests);
> > > > > +
> > > > > +       return std::max(count, min);
> > > > > +}
> > > > > diff --git a/src/v4l2/v4l2_camera.h b/src/v4l2/v4l2_camera.h
> > > > > index a095f4e27524..4b5618ac12b5 100644
> > > > > --- a/src/v4l2/v4l2_camera.h
> > > > > +++ b/src/v4l2/v4l2_camera.h
> > > > > @@ -45,8 +45,7 @@ public:
> > > > >         std::vector<Buffer> completedBuffers();
> > > > >
> > > > >         int configure(StreamConfiguration *streamConfigOut,
> > > > > -                     const Size &size, const PixelFormat &pixelformat,
> > > > > -                     unsigned int bufferCount);
> > > > > +                     const Size &size, const PixelFormat &pixelformat);
> > > > >         int validateConfiguration(const PixelFormat &pixelformat,
> > > > >                                   const Size &size,
> > > > >                                   StreamConfiguration *streamConfigOut);
> > > > > @@ -65,6 +64,8 @@ public:
> > > > >
> > > > >         bool isRunning();
> > > > >
> > > > > +       unsigned int minimumRequests(unsigned int count);
> > > > > +
> > > > >  private:
> > > > >         void requestComplete(Request *request);
> > > > >
> > > > > diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
> > > > > index 7682c4bddf90..634ec84e0cbb 100644
> > > > > --- a/src/v4l2/v4l2_camera_proxy.cpp
> > > > > +++ b/src/v4l2/v4l2_camera_proxy.cpp
> > > > > @@ -349,8 +349,7 @@ int V4L2CameraProxy::vidioc_s_fmt(V4L2CameraFile *file, struct v4l2_format *arg)
> > > > >         Size size(arg->fmt.pix.width, arg->fmt.pix.height);
> > > > >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(arg->fmt.pix.pixelformat);
> > > > >         ret = vcam_->configure(&streamConfig_, size,
> > > > > -                              PixelFormatInfo::info(v4l2Format).format,
> > > > > -                              bufferCount_);
> > > > > +                              PixelFormatInfo::info(v4l2Format).format);
> > > > >         if (ret < 0)
> > > > >                 return -EINVAL;
> > > > >
> > > > > @@ -491,14 +490,13 @@ int V4L2CameraProxy::vidioc_reqbufs(V4L2CameraFile *file, struct v4l2_requestbuf
> > > > >         Size size(v4l2PixFormat_.width, v4l2PixFormat_.height);
> > > > >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(v4l2PixFormat_.pixelformat);
> > > > >         int ret = vcam_->configure(&streamConfig_, size,
> > > > > -                                  PixelFormatInfo::info(v4l2Format).format,
> > > > > -                                  arg->count);
> > > > > +                                  PixelFormatInfo::info(v4l2Format).format);
> > > > >         if (ret < 0)
> > > > >                 return -EINVAL;
> > > > >
> > > > >         setFmtFromConfig(streamConfig_);
> > > > >
> > > > > -       arg->count = streamConfig_.bufferCount;
> > > > > +       arg->count = vcam_->minimumRequests(arg->count);
> > > > >         bufferCount_ = arg->count;
> > > > >
> > > > >         ret = vcam_->allocBuffers(arg->count);
> > > > > diff --git a/test/camera/buffer_import.cpp b/test/camera/buffer_import.cpp
> > > > > index c504ea09e64b..67ac0ad20e15 100644
> > > > > --- a/test/camera/buffer_import.cpp
> > > > > +++ b/test/camera/buffer_import.cpp
> > > > > @@ -16,6 +16,8 @@
> > > > >  #include <libcamera/base/thread.h>
> > > > >  #include <libcamera/base/timer.h>
> > > > >
> > > > > +#include <libcamera/property_ids.h>
> > > > > +
> > > > >  #include "libcamera/internal/device_enumerator.h"
> > > > >  #include "libcamera/internal/media_device.h"
> > > > >  #include "libcamera/internal/v4l2_videodevice.h"
> > > > > @@ -92,10 +94,12 @@ protected:
> > > > >                         return TestFail;
> > > > >                 }
> > > > >
> > > > > +               unsigned int bufferCount = camera_->properties().get(properties::MinimumRequests);
> > > > > +
> > > > >                 Stream *stream = cfg.stream();
> > > > >
> > > > >                 BufferSource source;
> > > > > -               int ret = source.allocate(cfg);
> > > > > +               int ret = source.allocate(cfg, bufferCount);
> > > > >                 if (ret != TestPass)
> > > > >                         return ret;
> > > > >
> > > > > @@ -139,10 +143,10 @@ protected:
> > > > >                 while (timer.isRunning())
> > > > >                         dispatcher->processEvents();
> > > > >
> > > > > -               if (completeRequestsCount_ < cfg.bufferCount * 2) {
> > > > > +               if (completeRequestsCount_ < bufferCount * 2) {
> > > > >                         std::cout << "Failed to capture enough frames (got "
> > > > >                                   << completeRequestsCount_ << " expected at least "
> > > > > -                                 << cfg.bufferCount * 2 << ")" << std::endl;
> > > > > +                                 << bufferCount * 2 << ")" << std::endl;
> > > > >                         return TestFail;
> > > > >                 }
> > > > >
> > > > > diff --git a/test/libtest/buffer_source.cpp b/test/libtest/buffer_source.cpp
> > > > > index 73563f2fc39d..c3d5286a2462 100644
> > > > > --- a/test/libtest/buffer_source.cpp
> > > > > +++ b/test/libtest/buffer_source.cpp
> > > > > @@ -24,7 +24,7 @@ BufferSource::~BufferSource()
> > > > >                 media_->release();
> > > > >  }
> > > > >
> > > > > -int BufferSource::allocate(const StreamConfiguration &config)
> > > > > +int BufferSource::allocate(const StreamConfiguration &config, unsigned int count)
> > > > >  {
> > > > >         /* Locate and open the video device. */
> > > > >         std::string videoDeviceName = "vivid-000-vid-out";
> > > > > @@ -77,7 +77,7 @@ int BufferSource::allocate(const StreamConfiguration &config)
> > > > >                 return TestFail;
> > > > >         }
> > > > >
> > > > > -       if (video->allocateBuffers(config.bufferCount, &buffers_) < 0) {
> > > > > +       if (video->allocateBuffers(count, &buffers_) < 0) {
> > > > >                 std::cout << "Failed to allocate buffers" << std::endl;
> > > > >                 return TestFail;
> > > > >         }
> > > > > diff --git a/test/libtest/buffer_source.h b/test/libtest/buffer_source.h
> > > > > index 14b4770e8d8a..6a18e269a575 100644
> > > > > --- a/test/libtest/buffer_source.h
> > > > > +++ b/test/libtest/buffer_source.h
> > > > > @@ -20,7 +20,7 @@ public:
> > > > >         BufferSource();
> > > > >         ~BufferSource();
> > > > >
> > > > > -       int allocate(const StreamConfiguration &config);
> > > > > +       int allocate(const StreamConfiguration &config, unsigned int count);
> > > > >         const std::vector<std::unique_ptr<FrameBuffer>> &buffers();
> > > > >
> > > > >  private:
> > > > > diff --git a/test/v4l2_videodevice/buffer_cache.cpp b/test/v4l2_videodevice/buffer_cache.cpp
> > > > > index b3f2bec11783..07fddfd2617c 100644
> > > > > --- a/test/v4l2_videodevice/buffer_cache.cpp
> > > > > +++ b/test/v4l2_videodevice/buffer_cache.cpp
> > > > > @@ -10,6 +10,7 @@
> > > > >  #include <vector>
> > > > >
> > > > >  #include <libcamera/formats.h>
> > > > > +#include <libcamera/property_ids.h>
> > > > >  #include <libcamera/stream.h>
> > > > >
> > > > >  #include "buffer_source.h"
> > > > > @@ -145,10 +146,9 @@ public:
> > > > >                 StreamConfiguration cfg;
> > > > >                 cfg.pixelFormat = formats::YUYV;
> > > > >                 cfg.size = Size(600, 800);
> > > > > -               cfg.bufferCount = numBuffers;
> > > > >
> > > > >                 BufferSource source;
> > > > > -               int ret = source.allocate(cfg);
> > > > > +               int ret = source.allocate(cfg, numBuffers);
> > > > >                 if (ret != TestPass)
> > > > >                         return ret;
> > > > >
> > > > > --
> > > > > 2.32.0
> > > > >

Hi David,

On Thu, Jul 29, 2021 at 11:00:33AM +0100, David Plowman wrote:
> Hi again
> 
> I thought that perhaps I could explain in more detail why I think
> applications need to be able to set (or influence) the buffer count
> and not leave it to the pipeline handler. My use-case is as follows.
> 
> I'm running some standard sort of application such as video recording
> for which there are maybe 4 buffers allocated. Now, I also want to do
> some image analysis that perhaps causes me to change something about
> the recording (maybe change camera settings, or even stop the
> recording). But this image analysis task is relatively slow.
> 
> One option is to copy the camera frames so that I can return the
> buffers in the request back to the camera. But copying images is
> generally undesirable. Instead I'd prefer to hold on to the buffer
> only now my camera pipeline is effectively working with only 3
> buffers, which is not enough. When I eventually finish with the buffer
> I will return it, and then grab the next one to keep again!

Ohh, I see. Sorry, I got a bit confused there, but this is not a problem at all.
If you want the pipeline to work with extra requests/buffers, you just supply
more to it :). Going back to your code snippet, this would be the change:
	
    configuration_ = camera_->generateConfiguration({ StreamRole::StillCapture });
-   configuration_->at(0).bufferCount = <value I have determined>;
    camera_->configure(configuration_.get());
    allocator_ = new FrameBufferAllocator(camera_);
    Stream *stream = configuration_->at(0).stream();
-   allocator_->allocate(stream);
+   allocator_->allocate(stream, <value I have determined>);
    // now allocator_->buffers(stream) has the buffers I want!

So, basically, you don't need to set bufferCount anymore, and instead you
allocate as many buffers as you need to give the pipeline handler by directly
passing the number to FrameBufferAllocator. In your case you want to allocate an
extra buffer to compensate for the one you'll be keeping.

It was already possible to supply the pipeline handler with how many
buffers you wanted, but previously you had to allocate them elsewhere, while now
you can allocate with the FrameBufferAllocator since it accepts the count
argument. (Actually for the raspberry pipeline it was already possible to do
this implicitly through bufferCount as you did, but not with the other
pipelines).

What I meant wasn't possible to change is how many internal buffers for metadata
and parameters the pipeline uses together with the IPA. And also how many V4L2
buffer slots are created to queue the requests into. But all of this is indeed
only relevant to the pipeline handler, so an application shouldn't care about
it. All of this, together with how many buffers the application would allocate,
was previously grouped on bufferCount. With its deletion, however, they are
getting split up.

I hope I got it right this time :).

Thanks,
Nícolas

> 
> So at the very least, the application needs to be able to say "please
> allocate <n> more buffers than you thought you needed". Does that make
> sense? Will this be possible in the new scheme?
> 
> Thanks!
> David
> 
> On Fri, 23 Jul 2021 at 22:08, Nícolas F. R. A. Prado
> <nfraprado@collabora.com> wrote:
> >
> > Hi David,
> >
> > On Fri, Jul 23, 2021 at 04:53:55PM +0100, David Plowman wrote:
> > > Hi Nicolas
> > >
> > > Thanks for the explanations. I'm still not sure I entirely understand
> > > so perhaps a quick look at how I would have to change my application
> > > code might help? Here's what I have now (I've removed any
> > > "unimportant" bits!):
> > >
> > > configuration_ = camera_->generateConfiguration({ StreamRole::StillCapture });
> > > configuration_->at(0).bufferCount = <value I have determined>;
> > > camera_->configure(configuration_.get());
> > > allocator_ = new FrameBufferAllocator(camera_);
> > > Stream *stream = configuration_->at(0).stream();
> > > allocator_->allocate(stream);
> > > // now allocator_->buffers(stream) has the buffers I want!
> > >
> > > I guess one thing to note is that the bufferCount value varies with
> > > more than just the StreamRole, and I don't in general trust the
> > > pipeline handler to "know" what I want. Will this still be possible?
> >
> > Oh I see... No, this won't be possible after we drop bufferCount. The
> > pipeline handler will decide for itself how many buffers to allocate internally,
> > possibly using the StreamRole as a hint.
> >
> > I wasn't aware this could impact an application, since all the other pipeline
> > handlers actually ignore when bufferCount is set by the application, overriding
> > it when the configuration is validated. But now I'm noticing the raspberrypi
> > pipeline actually uses it.
> >
> > Some context: This series actually began with me making
> > FrameBufferAllocator::allocate() receive a count argument instead of using the
> > value of bufferCount. But since Laurent mentioned that bufferCount was going
> > away eventually anyway I ended up removing it as well as part of this series.
> >
> > I do understand how being able to specify a bufferCount value that suits your
> > specific usecase is useful, though... Laurent, what's your take on this? :)
> >
> > Thanks,
> > Nícolas
> >
> > >
> > > Thanks!
> > > David
> > >
> > > On Fri, 23 Jul 2021 at 14:10, Nícolas F. R. A. Prado
> > > <nfraprado@collabora.com> wrote:
> > > >
> > > > Hi David,
> > > >
> > > > On Fri, Jul 23, 2021 at 09:42:56AM +0100, David Plowman wrote:
> > > > > Hi Nicolas
> > > > >
> > > > > Thanks very much for all this work! I was wondering if I could ask a
> > > > > little more about this patch. In our applications, for example, we set
> > > > > the bufferCount according to the use-case that the application is
> > > > > implementing. For example:
> > > > >
> > > > > * For preview windows we set bufferCount to 4.
> > > > > * For video capture we drop fewer frames with a deeper queue so we set it to 6.
> > > > > * For stills capture we can get by with one frame, though use cases
> > > > > that capture several stills images for fusion work better if we set
> > > > > bufferCount to 2 or 3.
> > > > >
> > > > > I was wondering how our applications can achieve this behaviour if the
> > > > > bufferCount field is no longer available.
> > > >
> > > > Okay, so the short answer is that the applications, knowing their particular use
> > > > case, are responsible to provide enough requests to keep the pipeline going. On
> > > > the pipeline handler side, it's free to use how many internal buffers it wants.
> > > >
> > > > So in your case, the pipeline handler could still allocate that same number of
> > > > internal buffers as you previously did based on bufferCount, but now based
> > > > solely on the StreamRole set. The application would then allocate and queue
> > > > how many buffers fits the usage. (Note that before the application would call
> > > > FrameBufferAllocator::allocate() and it would allocate 'bufferCount' buffers,
> > > > but now the function takes a count argument so the application is free to choose
> > > > how many)
> > > >
> > > > Now, I guess it would be nice for the application to be able to query what is a
> > > > good number of buffers to use, for example 6 in the video capture of your use
> > > > case. At the moment, the only information available is that 1 is the minimum
> > > > number of buffers required. So the application would have to know that 6 is a
> > > > good number for video capture. Maybe another property could be introduced later
> > > > for this recommended amount, but previous discussions suggested this is very use
> > > > case dependent, so might not make sense.
> > > >
> > > > I hope this answers the question. If not, I'm still here :).
> > > >
> > > > Thanks,
> > > > Nícolas
> > > >
> > > > >
> > > > > Thanks!
> > > > > David
> > > > >
> > > > > On Fri, 23 Jul 2021 at 00:29, Nícolas F. R. A. Prado
> > > > > <nfraprado@collabora.com> wrote:
> > > > > >
> > > > > > Now that the number of buffers allocated by the FrameBufferAllocator
> > > > > > helper is passed through FrameBufferAllocator::allocate() and the
> > > > > > pipelines no longer use bufferCount for internal buffer or V4L2 buffer
> > > > > > slots allocation, we no longer need to have bufferCount in the
> > > > > > StreamConfiguration, so remove it.
> > > > > >
> > > > > > Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> > > > > > ---
> > > > > >
> > > > > > No changes in v7
> > > > > >
> > > > > > Changes in v6:
> > > > > > - Removed IPU3_BUFFER_COUNT as it was unused
> > > > > >
> > > > > >  include/libcamera/stream.h                         |  2 --
> > > > > >  src/android/camera_stream.cpp                      |  2 +-
> > > > > >  src/libcamera/pipeline/ipu3/cio2.cpp               |  1 -
> > > > > >  src/libcamera/pipeline/ipu3/ipu3.cpp               |  8 --------
> > > > > >  src/libcamera/pipeline/raspberrypi/raspberrypi.cpp |  6 ------
> > > > > >  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp      |  2 --
> > > > > >  src/libcamera/pipeline/simple/converter.cpp        |  3 ---
> > > > > >  src/libcamera/pipeline/simple/converter.h          |  3 ---
> > > > > >  src/libcamera/pipeline/simple/simple.cpp           |  5 +----
> > > > > >  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp       |  3 ---
> > > > > >  src/libcamera/pipeline/vimc/vimc.cpp               |  3 ---
> > > > > >  src/libcamera/stream.cpp                           |  9 ++-------
> > > > > >  src/v4l2/v4l2_camera.cpp                           | 14 ++++++++++----
> > > > > >  src/v4l2/v4l2_camera.h                             |  5 +++--
> > > > > >  src/v4l2/v4l2_camera_proxy.cpp                     |  8 +++-----
> > > > > >  test/camera/buffer_import.cpp                      | 10 +++++++---
> > > > > >  test/libtest/buffer_source.cpp                     |  4 ++--
> > > > > >  test/libtest/buffer_source.h                       |  2 +-
> > > > > >  test/v4l2_videodevice/buffer_cache.cpp             |  4 ++--
> > > > > >  19 files changed, 32 insertions(+), 62 deletions(-)
> > > > > >
> > > > > > diff --git a/include/libcamera/stream.h b/include/libcamera/stream.h
> > > > > > index 0c55e7164592..b25f0059f2f1 100644
> > > > > > --- a/include/libcamera/stream.h
> > > > > > +++ b/include/libcamera/stream.h
> > > > > > @@ -45,8 +45,6 @@ struct StreamConfiguration {
> > > > > >         unsigned int stride;
> > > > > >         unsigned int frameSize;
> > > > > >
> > > > > > -       unsigned int bufferCount;
> > > > > > -
> > > > > >         Stream *stream() const { return stream_; }
> > > > > >         void setStream(Stream *stream) { stream_ = stream; }
> > > > > >         const StreamFormats &formats() const { return formats_; }
> > > > > > diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
> > > > > > index b168e3c0c288..0794be409f82 100644
> > > > > > --- a/src/android/camera_stream.cpp
> > > > > > +++ b/src/android/camera_stream.cpp
> > > > > > @@ -94,7 +94,7 @@ int CameraStream::configure()
> > > > > >                         buffers_.push_back(frameBuffer.get());
> > > > > >         }
> > > > > >
> > > > > > -       camera3Stream_->max_buffers = configuration().bufferCount;
> > > > > > +       camera3Stream_->max_buffers = bufferCount;
> > > > > >
> > > > > >         return 0;
> > > > > >  }
> > > > > > diff --git a/src/libcamera/pipeline/ipu3/cio2.cpp b/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > > > index 1bcd580e251c..0e04e7214489 100644
> > > > > > --- a/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > > > +++ b/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > > > @@ -214,7 +214,6 @@ StreamConfiguration CIO2Device::generateConfiguration(Size size) const
> > > > > >
> > > > > >         cfg.size = sensorFormat.size;
> > > > > >         cfg.pixelFormat = mbusCodesToPixelFormat.at(sensorFormat.mbus_code);
> > > > > > -       cfg.bufferCount = CIO2_BUFFER_COUNT;
> > > > > >
> > > > > >         return cfg;
> > > > > >  }
> > > > > > diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > > index 4efd201c05e5..b223b3f33cd0 100644
> > > > > > --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > > +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > > @@ -38,7 +38,6 @@ namespace libcamera {
> > > > > >
> > > > > >  LOG_DEFINE_CATEGORY(IPU3)
> > > > > >
> > > > > > -static constexpr unsigned int IPU3_BUFFER_COUNT = 4;
> > > > > >  static constexpr unsigned int IPU3_MAX_STREAMS = 3;
> > > > > >  static const Size IMGU_OUTPUT_MIN_SIZE = { 2, 2 };
> > > > > >  static const Size IMGU_OUTPUT_MAX_SIZE = { 4480, 34004 };
> > > > > > @@ -295,7 +294,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > > > > >                         /* Initialize the RAW stream with the CIO2 configuration. */
> > > > > >                         cfg->size = cio2Configuration_.size;
> > > > > >                         cfg->pixelFormat = cio2Configuration_.pixelFormat;
> > > > > > -                       cfg->bufferCount = cio2Configuration_.bufferCount;
> > > > > >                         cfg->stride = info.stride(cfg->size.width, 0, 64);
> > > > > >                         cfg->frameSize = info.frameSize(cfg->size, 64);
> > > > > >                         cfg->setStream(const_cast<Stream *>(&data_->rawStream_));
> > > > > > @@ -339,7 +337,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > > > > >                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> > > > > >
> > > > > >                         cfg->pixelFormat = formats::NV12;
> > > > > > -                       cfg->bufferCount = IPU3_BUFFER_COUNT;
> > > > > >                         cfg->stride = info.stride(cfg->size.width, 0, 1);
> > > > > >                         cfg->frameSize = info.frameSize(cfg->size, 1);
> > > > > >
> > > > > > @@ -407,7 +404,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > >         Size sensorResolution = data->cio2_.sensor()->resolution();
> > > > > >         for (const StreamRole role : roles) {
> > > > > >                 std::map<PixelFormat, std::vector<SizeRange>> streamFormats;
> > > > > > -               unsigned int bufferCount;
> > > > > >                 PixelFormat pixelFormat;
> > > > > >                 Size size;
> > > > > >
> > > > > > @@ -428,7 +424,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > >                         size.height = utils::alignDown(size.height - 1,
> > > > > >                                                        IMGU_OUTPUT_HEIGHT_MARGIN);
> > > > > >                         pixelFormat = formats::NV12;
> > > > > > -                       bufferCount = IPU3_BUFFER_COUNT;
> > > > > >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> > > > > >
> > > > > >                         break;
> > > > > > @@ -438,7 +433,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > >                                 data->cio2_.generateConfiguration(sensorResolution);
> > > > > >                         pixelFormat = cio2Config.pixelFormat;
> > > > > >                         size = cio2Config.size;
> > > > > > -                       bufferCount = cio2Config.bufferCount;
> > > > > >
> > > > > >                         for (const PixelFormat &format : data->cio2_.formats())
> > > > > >                                 streamFormats[format] = data->cio2_.sizes();
> > > > > > @@ -457,7 +451,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > >                                                .alignedDownTo(IMGU_OUTPUT_WIDTH_ALIGN,
> > > > > >                                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> > > > > >                         pixelFormat = formats::NV12;
> > > > > > -                       bufferCount = IPU3_BUFFER_COUNT;
> > > > > >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> > > > > >
> > > > > >                         break;
> > > > > > @@ -474,7 +467,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > >                 StreamConfiguration cfg(formats);
> > > > > >                 cfg.size = size;
> > > > > >                 cfg.pixelFormat = pixelFormat;
> > > > > > -               cfg.bufferCount = bufferCount;
> > > > > >                 config->addConfiguration(cfg);
> > > > > >         }
> > > > > >
> > > > > > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > > index 776e0f92aed1..e6fc0425c3ef 100644
> > > > > > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > > @@ -473,7 +473,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > >         RPiCameraData *data = cameraData(camera);
> > > > > >         CameraConfiguration *config = new RPiCameraConfiguration(data);
> > > > > >         V4L2DeviceFormat sensorFormat;
> > > > > > -       unsigned int bufferCount;
> > > > > >         PixelFormat pixelFormat;
> > > > > >         V4L2VideoDevice::Formats fmts;
> > > > > >         Size size;
> > > > > > @@ -491,7 +490,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > >                         sensorFormat = findBestMode(fmts, size);
> > > > > >                         pixelFormat = sensorFormat.fourcc.toPixelFormat();
> > > > > >                         ASSERT(pixelFormat.isValid());
> > > > > > -                       bufferCount = 2;
> > > > > >                         rawCount++;
> > > > > >                         break;
> > > > > >
> > > > > > @@ -500,7 +498,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > >                         pixelFormat = formats::NV12;
> > > > > >                         /* Return the largest sensor resolution. */
> > > > > >                         size = data->sensor_->resolution();
> > > > > > -                       bufferCount = 1;
> > > > > >                         outCount++;
> > > > > >                         break;
> > > > > >
> > > > > > @@ -516,7 +513,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> > > > > >                         pixelFormat = formats::YUV420;
> > > > > >                         size = { 1920, 1080 };
> > > > > > -                       bufferCount = 4;
> > > > > >                         outCount++;
> > > > > >                         break;
> > > > > >
> > > > > > @@ -524,7 +520,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> > > > > >                         pixelFormat = formats::ARGB8888;
> > > > > >                         size = { 800, 600 };
> > > > > > -                       bufferCount = 4;
> > > > > >                         outCount++;
> > > > > >                         break;
> > > > > >
> > > > > > @@ -554,7 +549,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > >                 StreamConfiguration cfg(formats);
> > > > > >                 cfg.size = size;
> > > > > >                 cfg.pixelFormat = pixelFormat;
> > > > > > -               cfg.bufferCount = bufferCount;
> > > > > >                 config->addConfiguration(cfg);
> > > > > >         }
> > > > > >
> > > > > > diff --git a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > > > index fea330f72886..4961f3971e59 100644
> > > > > > --- a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > > > +++ b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > > > @@ -61,7 +61,6 @@ StreamConfiguration RkISP1Path::generateConfiguration(const Size &resolution)
> > > > > >         StreamConfiguration cfg(formats);
> > > > > >         cfg.pixelFormat = formats::NV12;
> > > > > >         cfg.size = maxResolution;
> > > > > > -       cfg.bufferCount = RKISP1_BUFFER_COUNT;
> > > > > >
> > > > > >         return cfg;
> > > > > >  }
> > > > > > @@ -77,7 +76,6 @@ CameraConfiguration::Status RkISP1Path::validate(StreamConfiguration *cfg)
> > > > > >
> > > > > >         cfg->size.boundTo(maxResolution_);
> > > > > >         cfg->size.expandTo(minResolution_);
> > > > > > -       cfg->bufferCount = RKISP1_BUFFER_COUNT;
> > > > > >
> > > > > >         V4L2DeviceFormat format;
> > > > > >         format.fourcc = video_->toV4L2PixelFormat(cfg->pixelFormat);
> > > > > > diff --git a/src/libcamera/pipeline/simple/converter.cpp b/src/libcamera/pipeline/simple/converter.cpp
> > > > > > index b3bcf01483f7..fda417793e80 100644
> > > > > > --- a/src/libcamera/pipeline/simple/converter.cpp
> > > > > > +++ b/src/libcamera/pipeline/simple/converter.cpp
> > > > > > @@ -89,9 +89,6 @@ int SimpleConverter::Stream::configure(const StreamConfiguration &inputCfg,
> > > > > >                 return -EINVAL;
> > > > > >         }
> > > > > >
> > > > > > -       inputBufferCount_ = inputCfg.bufferCount;
> > > > > > -       outputBufferCount_ = outputCfg.bufferCount;
> > > > > > -
> > > > > >         return 0;
> > > > > >  }
> > > > > >
> > > > > > diff --git a/src/libcamera/pipeline/simple/converter.h b/src/libcamera/pipeline/simple/converter.h
> > > > > > index 7e1d60674f62..406e63ca2a80 100644
> > > > > > --- a/src/libcamera/pipeline/simple/converter.h
> > > > > > +++ b/src/libcamera/pipeline/simple/converter.h
> > > > > > @@ -87,9 +87,6 @@ private:
> > > > > >                 SimpleConverter *converter_;
> > > > > >                 unsigned int index_;
> > > > > >                 std::unique_ptr<V4L2M2MDevice> m2m_;
> > > > > > -
> > > > > > -               unsigned int inputBufferCount_;
> > > > > > -               unsigned int outputBufferCount_;
> > > > > >         };
> > > > > >
> > > > > >         std::string deviceNode_;
> > > > > > diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> > > > > > index a1163eaf8be2..ded04914f610 100644
> > > > > > --- a/src/libcamera/pipeline/simple/simple.cpp
> > > > > > +++ b/src/libcamera/pipeline/simple/simple.cpp
> > > > > > @@ -628,7 +628,7 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> > > > > >                     cfg.size != pipeConfig_->captureSize)
> > > > > >                         needConversion_ = true;
> > > > > >
> > > > > > -               /* Set the stride, frameSize and bufferCount. */
> > > > > > +               /* Set the stride and frameSize. */
> > > > > >                 if (needConversion_) {
> > > > > >                         std::tie(cfg.stride, cfg.frameSize) =
> > > > > >                                 converter->strideAndFrameSize(cfg.pixelFormat, cfg.size);
> > > > > > @@ -646,8 +646,6 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> > > > > >                         cfg.stride = format.planes[0].bpl;
> > > > > >                         cfg.frameSize = format.planes[0].size;
> > > > > >                 }
> > > > > > -
> > > > > > -               cfg.bufferCount = 3;
> > > > > >         }
> > > > > >
> > > > > >         return status;
> > > > > > @@ -770,7 +768,6 @@ int SimplePipelineHandler::configure(Camera *camera, CameraConfiguration *c)
> > > > > >         inputCfg.pixelFormat = pipeConfig->captureFormat;
> > > > > >         inputCfg.size = pipeConfig->captureSize;
> > > > > >         inputCfg.stride = captureFormat.planes[0].bpl;
> > > > > > -       inputCfg.bufferCount = kNumInternalBuffers;
> > > > > >
> > > > > >         return converter_->configure(inputCfg, outputCfgs);
> > > > > >  }
> > > > > > diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > > > index 755949e7a59a..32482300f09a 100644
> > > > > > --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > > > +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > > > @@ -150,8 +150,6 @@ CameraConfiguration::Status UVCCameraConfiguration::validate()
> > > > > >                 status = Adjusted;
> > > > > >         }
> > > > > >
> > > > > > -       cfg.bufferCount = 4;
> > > > > > -
> > > > > >         V4L2DeviceFormat format;
> > > > > >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> > > > > >         format.size = cfg.size;
> > > > > > @@ -193,7 +191,6 @@ CameraConfiguration *PipelineHandlerUVC::generateConfiguration(Camera *camera,
> > > > > >
> > > > > >         cfg.pixelFormat = formats.pixelformats().front();
> > > > > >         cfg.size = formats.sizes(cfg.pixelFormat).back();
> > > > > > -       cfg.bufferCount = 4;
> > > > > >
> > > > > >         config->addConfiguration(cfg);
> > > > > >
> > > > > > diff --git a/src/libcamera/pipeline/vimc/vimc.cpp b/src/libcamera/pipeline/vimc/vimc.cpp
> > > > > > index 24ba743a946c..a698427c4361 100644
> > > > > > --- a/src/libcamera/pipeline/vimc/vimc.cpp
> > > > > > +++ b/src/libcamera/pipeline/vimc/vimc.cpp
> > > > > > @@ -167,8 +167,6 @@ CameraConfiguration::Status VimcCameraConfiguration::validate()
> > > > > >                 status = Adjusted;
> > > > > >         }
> > > > > >
> > > > > > -       cfg.bufferCount = 4;
> > > > > > -
> > > > > >         V4L2DeviceFormat format;
> > > > > >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> > > > > >         format.size = cfg.size;
> > > > > > @@ -224,7 +222,6 @@ CameraConfiguration *PipelineHandlerVimc::generateConfiguration(Camera *camera,
> > > > > >
> > > > > >         cfg.pixelFormat = formats::BGR888;
> > > > > >         cfg.size = { 1920, 1080 };
> > > > > > -       cfg.bufferCount = 4;
> > > > > >
> > > > > >         config->addConfiguration(cfg);
> > > > > >
> > > > > > diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
> > > > > > index b8626775d224..ca507b72b26a 100644
> > > > > > --- a/src/libcamera/stream.cpp
> > > > > > +++ b/src/libcamera/stream.cpp
> > > > > > @@ -280,7 +280,7 @@ SizeRange StreamFormats::range(const PixelFormat &pixelformat) const
> > > > > >   * handlers provide StreamFormats.
> > > > > >   */
> > > > > >  StreamConfiguration::StreamConfiguration()
> > > > > > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > > > > > +       : pixelFormat(0), stride(0), frameSize(0),
> > > > > >           stream_(nullptr)
> > > > > >  {
> > > > > >  }
> > > > > > @@ -289,7 +289,7 @@ StreamConfiguration::StreamConfiguration()
> > > > > >   * \brief Construct a configuration with stream formats
> > > > > >   */
> > > > > >  StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > > > > > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > > > > > +       : pixelFormat(0), stride(0), frameSize(0),
> > > > > >           stream_(nullptr), formats_(formats)
> > > > > >  {
> > > > > >  }
> > > > > > @@ -324,11 +324,6 @@ StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > > > > >   * validating the configuration with a call to CameraConfiguration::validate().
> > > > > >   */
> > > > > >
> > > > > > -/**
> > > > > > - * \var StreamConfiguration::bufferCount
> > > > > > - * \brief Requested number of buffers to allocate for the stream
> > > > > > - */
> > > > > > -
> > > > > >  /**
> > > > > >   * \fn StreamConfiguration::stream()
> > > > > >   * \brief Retrieve the stream associated with the configuration
> > > > > > diff --git a/src/v4l2/v4l2_camera.cpp b/src/v4l2/v4l2_camera.cpp
> > > > > > index d01eacfa2b84..2ff9affc6388 100644
> > > > > > --- a/src/v4l2/v4l2_camera.cpp
> > > > > > +++ b/src/v4l2/v4l2_camera.cpp
> > > > > > @@ -12,6 +12,8 @@
> > > > > >
> > > > > >  #include <libcamera/base/log.h>
> > > > > >
> > > > > > +#include <libcamera/property_ids.h>
> > > > > > +
> > > > > >  using namespace libcamera;
> > > > > >
> > > > > >  LOG_DECLARE_CATEGORY(V4L2Compat)
> > > > > > @@ -107,14 +109,12 @@ void V4L2Camera::requestComplete(Request *request)
> > > > > >  }
> > > > > >
> > > > > >  int V4L2Camera::configure(StreamConfiguration *streamConfigOut,
> > > > > > -                         const Size &size, const PixelFormat &pixelformat,
> > > > > > -                         unsigned int bufferCount)
> > > > > > +                         const Size &size, const PixelFormat &pixelformat)
> > > > > >  {
> > > > > >         StreamConfiguration &streamConfig = config_->at(0);
> > > > > >         streamConfig.size.width = size.width;
> > > > > >         streamConfig.size.height = size.height;
> > > > > >         streamConfig.pixelFormat = pixelformat;
> > > > > > -       streamConfig.bufferCount = bufferCount;
> > > > > >         /* \todo memoryType (interval vs external) */
> > > > > >
> > > > > >         CameraConfiguration::Status validation = config_->validate();
> > > > > > @@ -146,7 +146,6 @@ int V4L2Camera::validateConfiguration(const PixelFormat &pixelFormat,
> > > > > >         StreamConfiguration &cfg = config->at(0);
> > > > > >         cfg.size = size;
> > > > > >         cfg.pixelFormat = pixelFormat;
> > > > > > -       cfg.bufferCount = 1;
> > > > > >
> > > > > >         CameraConfiguration::Status validation = config->validate();
> > > > > >         if (validation == CameraConfiguration::Invalid)
> > > > > > @@ -299,3 +298,10 @@ bool V4L2Camera::isRunning()
> > > > > >  {
> > > > > >         return isRunning_;
> > > > > >  }
> > > > > > +
> > > > > > +unsigned int V4L2Camera::minimumRequests(unsigned int count)
> > > > > > +{
> > > > > > +       unsigned int min = camera_->properties().get(properties::MinimumRequests);
> > > > > > +
> > > > > > +       return std::max(count, min);
> > > > > > +}
> > > > > > diff --git a/src/v4l2/v4l2_camera.h b/src/v4l2/v4l2_camera.h
> > > > > > index a095f4e27524..4b5618ac12b5 100644
> > > > > > --- a/src/v4l2/v4l2_camera.h
> > > > > > +++ b/src/v4l2/v4l2_camera.h
> > > > > > @@ -45,8 +45,7 @@ public:
> > > > > >         std::vector<Buffer> completedBuffers();
> > > > > >
> > > > > >         int configure(StreamConfiguration *streamConfigOut,
> > > > > > -                     const Size &size, const PixelFormat &pixelformat,
> > > > > > -                     unsigned int bufferCount);
> > > > > > +                     const Size &size, const PixelFormat &pixelformat);
> > > > > >         int validateConfiguration(const PixelFormat &pixelformat,
> > > > > >                                   const Size &size,
> > > > > >                                   StreamConfiguration *streamConfigOut);
> > > > > > @@ -65,6 +64,8 @@ public:
> > > > > >
> > > > > >         bool isRunning();
> > > > > >
> > > > > > +       unsigned int minimumRequests(unsigned int count);
> > > > > > +
> > > > > >  private:
> > > > > >         void requestComplete(Request *request);
> > > > > >
> > > > > > diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
> > > > > > index 7682c4bddf90..634ec84e0cbb 100644
> > > > > > --- a/src/v4l2/v4l2_camera_proxy.cpp
> > > > > > +++ b/src/v4l2/v4l2_camera_proxy.cpp
> > > > > > @@ -349,8 +349,7 @@ int V4L2CameraProxy::vidioc_s_fmt(V4L2CameraFile *file, struct v4l2_format *arg)
> > > > > >         Size size(arg->fmt.pix.width, arg->fmt.pix.height);
> > > > > >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(arg->fmt.pix.pixelformat);
> > > > > >         ret = vcam_->configure(&streamConfig_, size,
> > > > > > -                              PixelFormatInfo::info(v4l2Format).format,
> > > > > > -                              bufferCount_);
> > > > > > +                              PixelFormatInfo::info(v4l2Format).format);
> > > > > >         if (ret < 0)
> > > > > >                 return -EINVAL;
> > > > > >
> > > > > > @@ -491,14 +490,13 @@ int V4L2CameraProxy::vidioc_reqbufs(V4L2CameraFile *file, struct v4l2_requestbuf
> > > > > >         Size size(v4l2PixFormat_.width, v4l2PixFormat_.height);
> > > > > >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(v4l2PixFormat_.pixelformat);
> > > > > >         int ret = vcam_->configure(&streamConfig_, size,
> > > > > > -                                  PixelFormatInfo::info(v4l2Format).format,
> > > > > > -                                  arg->count);
> > > > > > +                                  PixelFormatInfo::info(v4l2Format).format);
> > > > > >         if (ret < 0)
> > > > > >                 return -EINVAL;
> > > > > >
> > > > > >         setFmtFromConfig(streamConfig_);
> > > > > >
> > > > > > -       arg->count = streamConfig_.bufferCount;
> > > > > > +       arg->count = vcam_->minimumRequests(arg->count);
> > > > > >         bufferCount_ = arg->count;
> > > > > >
> > > > > >         ret = vcam_->allocBuffers(arg->count);
> > > > > > diff --git a/test/camera/buffer_import.cpp b/test/camera/buffer_import.cpp
> > > > > > index c504ea09e64b..67ac0ad20e15 100644
> > > > > > --- a/test/camera/buffer_import.cpp
> > > > > > +++ b/test/camera/buffer_import.cpp
> > > > > > @@ -16,6 +16,8 @@
> > > > > >  #include <libcamera/base/thread.h>
> > > > > >  #include <libcamera/base/timer.h>
> > > > > >
> > > > > > +#include <libcamera/property_ids.h>
> > > > > > +
> > > > > >  #include "libcamera/internal/device_enumerator.h"
> > > > > >  #include "libcamera/internal/media_device.h"
> > > > > >  #include "libcamera/internal/v4l2_videodevice.h"
> > > > > > @@ -92,10 +94,12 @@ protected:
> > > > > >                         return TestFail;
> > > > > >                 }
> > > > > >
> > > > > > +               unsigned int bufferCount = camera_->properties().get(properties::MinimumRequests);
> > > > > > +
> > > > > >                 Stream *stream = cfg.stream();
> > > > > >
> > > > > >                 BufferSource source;
> > > > > > -               int ret = source.allocate(cfg);
> > > > > > +               int ret = source.allocate(cfg, bufferCount);
> > > > > >                 if (ret != TestPass)
> > > > > >                         return ret;
> > > > > >
> > > > > > @@ -139,10 +143,10 @@ protected:
> > > > > >                 while (timer.isRunning())
> > > > > >                         dispatcher->processEvents();
> > > > > >
> > > > > > -               if (completeRequestsCount_ < cfg.bufferCount * 2) {
> > > > > > +               if (completeRequestsCount_ < bufferCount * 2) {
> > > > > >                         std::cout << "Failed to capture enough frames (got "
> > > > > >                                   << completeRequestsCount_ << " expected at least "
> > > > > > -                                 << cfg.bufferCount * 2 << ")" << std::endl;
> > > > > > +                                 << bufferCount * 2 << ")" << std::endl;
> > > > > >                         return TestFail;
> > > > > >                 }
> > > > > >
> > > > > > diff --git a/test/libtest/buffer_source.cpp b/test/libtest/buffer_source.cpp
> > > > > > index 73563f2fc39d..c3d5286a2462 100644
> > > > > > --- a/test/libtest/buffer_source.cpp
> > > > > > +++ b/test/libtest/buffer_source.cpp
> > > > > > @@ -24,7 +24,7 @@ BufferSource::~BufferSource()
> > > > > >                 media_->release();
> > > > > >  }
> > > > > >
> > > > > > -int BufferSource::allocate(const StreamConfiguration &config)
> > > > > > +int BufferSource::allocate(const StreamConfiguration &config, unsigned int count)
> > > > > >  {
> > > > > >         /* Locate and open the video device. */
> > > > > >         std::string videoDeviceName = "vivid-000-vid-out";
> > > > > > @@ -77,7 +77,7 @@ int BufferSource::allocate(const StreamConfiguration &config)
> > > > > >                 return TestFail;
> > > > > >         }
> > > > > >
> > > > > > -       if (video->allocateBuffers(config.bufferCount, &buffers_) < 0) {
> > > > > > +       if (video->allocateBuffers(count, &buffers_) < 0) {
> > > > > >                 std::cout << "Failed to allocate buffers" << std::endl;
> > > > > >                 return TestFail;
> > > > > >         }
> > > > > > diff --git a/test/libtest/buffer_source.h b/test/libtest/buffer_source.h
> > > > > > index 14b4770e8d8a..6a18e269a575 100644
> > > > > > --- a/test/libtest/buffer_source.h
> > > > > > +++ b/test/libtest/buffer_source.h
> > > > > > @@ -20,7 +20,7 @@ public:
> > > > > >         BufferSource();
> > > > > >         ~BufferSource();
> > > > > >
> > > > > > -       int allocate(const StreamConfiguration &config);
> > > > > > +       int allocate(const StreamConfiguration &config, unsigned int count);
> > > > > >         const std::vector<std::unique_ptr<FrameBuffer>> &buffers();
> > > > > >
> > > > > >  private:
> > > > > > diff --git a/test/v4l2_videodevice/buffer_cache.cpp b/test/v4l2_videodevice/buffer_cache.cpp
> > > > > > index b3f2bec11783..07fddfd2617c 100644
> > > > > > --- a/test/v4l2_videodevice/buffer_cache.cpp
> > > > > > +++ b/test/v4l2_videodevice/buffer_cache.cpp
> > > > > > @@ -10,6 +10,7 @@
> > > > > >  #include <vector>
> > > > > >
> > > > > >  #include <libcamera/formats.h>
> > > > > > +#include <libcamera/property_ids.h>
> > > > > >  #include <libcamera/stream.h>
> > > > > >
> > > > > >  #include "buffer_source.h"
> > > > > > @@ -145,10 +146,9 @@ public:
> > > > > >                 StreamConfiguration cfg;
> > > > > >                 cfg.pixelFormat = formats::YUYV;
> > > > > >                 cfg.size = Size(600, 800);
> > > > > > -               cfg.bufferCount = numBuffers;
> > > > > >
> > > > > >                 BufferSource source;
> > > > > > -               int ret = source.allocate(cfg);
> > > > > > +               int ret = source.allocate(cfg, numBuffers);
> > > > > >                 if (ret != TestPass)
> > > > > >                         return ret;
> > > > > >
> > > > > > --
> > > > > > 2.32.0
> > > > > >

Ah, OK, that sounds straightforward, then. Thanks for the explanation!

Best regards
David

On Thu, 29 Jul 2021 at 15:38, Nícolas F. R. A. Prado
<nfraprado@collabora.com> wrote:
>
> Hi David,
>
> On Thu, Jul 29, 2021 at 11:00:33AM +0100, David Plowman wrote:
> > Hi again
> >
> > I thought that perhaps I could explain in more detail why I think
> > applications need to be able to set (or influence) the buffer count
> > and not leave it to the pipeline handler. My use-case is as follows.
> >
> > I'm running some standard sort of application such as video recording
> > for which there are maybe 4 buffers allocated. Now, I also want to do
> > some image analysis that perhaps causes me to change something about
> > the recording (maybe change camera settings, or even stop the
> > recording). But this image analysis task is relatively slow.
> >
> > One option is to copy the camera frames so that I can return the
> > buffers in the request back to the camera. But copying images is
> > generally undesirable. Instead I'd prefer to hold on to the buffer
> > only now my camera pipeline is effectively working with only 3
> > buffers, which is not enough. When I eventually finish with the buffer
> > I will return it, and then grab the next one to keep again!
>
> Ohh, I see. Sorry, I got a bit confused there, but this is not a problem at all.
> If you want the pipeline to work with extra requests/buffers, you just supply
> more to it :). Going back to your code snippet, this would be the change:
>
>     configuration_ = camera_->generateConfiguration({ StreamRole::StillCapture });
> -   configuration_->at(0).bufferCount = <value I have determined>;
>     camera_->configure(configuration_.get());
>     allocator_ = new FrameBufferAllocator(camera_);
>     Stream *stream = configuration_->at(0).stream();
> -   allocator_->allocate(stream);
> +   allocator_->allocate(stream, <value I have determined>);
>     // now allocator_->buffers(stream) has the buffers I want!
>
> So, basically, you don't need to set bufferCount anymore, and instead you
> allocate as many buffers as you need to give the pipeline handler by directly
> passing the number to FrameBufferAllocator. In your case you want to allocate an
> extra buffer to compensate for the one you'll be keeping.
>
> It was already possible to supply the pipeline handler with how many
> buffers you wanted, but previously you had to allocate them elsewhere, while now
> you can allocate with the FrameBufferAllocator since it accepts the count
> argument. (Actually for the raspberry pipeline it was already possible to do
> this implicitly through bufferCount as you did, but not with the other
> pipelines).
>
> What I meant wasn't possible to change is how many internal buffers for metadata
> and parameters the pipeline uses together with the IPA. And also how many V4L2
> buffer slots are created to queue the requests into. But all of this is indeed
> only relevant to the pipeline handler, so an application shouldn't care about
> it. All of this, together with how many buffers the application would allocate,
> was previously grouped on bufferCount. With its deletion, however, they are
> getting split up.
>
> I hope I got it right this time :).
>
> Thanks,
> Nícolas
>
> >
> > So at the very least, the application needs to be able to say "please
> > allocate <n> more buffers than you thought you needed". Does that make
> > sense? Will this be possible in the new scheme?
> >
> > Thanks!
> > David
> >
> > On Fri, 23 Jul 2021 at 22:08, Nícolas F. R. A. Prado
> > <nfraprado@collabora.com> wrote:
> > >
> > > Hi David,
> > >
> > > On Fri, Jul 23, 2021 at 04:53:55PM +0100, David Plowman wrote:
> > > > Hi Nicolas
> > > >
> > > > Thanks for the explanations. I'm still not sure I entirely understand
> > > > so perhaps a quick look at how I would have to change my application
> > > > code might help? Here's what I have now (I've removed any
> > > > "unimportant" bits!):
> > > >
> > > > configuration_ = camera_->generateConfiguration({ StreamRole::StillCapture });
> > > > configuration_->at(0).bufferCount = <value I have determined>;
> > > > camera_->configure(configuration_.get());
> > > > allocator_ = new FrameBufferAllocator(camera_);
> > > > Stream *stream = configuration_->at(0).stream();
> > > > allocator_->allocate(stream);
> > > > // now allocator_->buffers(stream) has the buffers I want!
> > > >
> > > > I guess one thing to note is that the bufferCount value varies with
> > > > more than just the StreamRole, and I don't in general trust the
> > > > pipeline handler to "know" what I want. Will this still be possible?
> > >
> > > Oh I see... No, this won't be possible after we drop bufferCount. The
> > > pipeline handler will decide for itself how many buffers to allocate internally,
> > > possibly using the StreamRole as a hint.
> > >
> > > I wasn't aware this could impact an application, since all the other pipeline
> > > handlers actually ignore when bufferCount is set by the application, overriding
> > > it when the configuration is validated. But now I'm noticing the raspberrypi
> > > pipeline actually uses it.
> > >
> > > Some context: This series actually began with me making
> > > FrameBufferAllocator::allocate() receive a count argument instead of using the
> > > value of bufferCount. But since Laurent mentioned that bufferCount was going
> > > away eventually anyway I ended up removing it as well as part of this series.
> > >
> > > I do understand how being able to specify a bufferCount value that suits your
> > > specific usecase is useful, though... Laurent, what's your take on this? :)
> > >
> > > Thanks,
> > > Nícolas
> > >
> > > >
> > > > Thanks!
> > > > David
> > > >
> > > > On Fri, 23 Jul 2021 at 14:10, Nícolas F. R. A. Prado
> > > > <nfraprado@collabora.com> wrote:
> > > > >
> > > > > Hi David,
> > > > >
> > > > > On Fri, Jul 23, 2021 at 09:42:56AM +0100, David Plowman wrote:
> > > > > > Hi Nicolas
> > > > > >
> > > > > > Thanks very much for all this work! I was wondering if I could ask a
> > > > > > little more about this patch. In our applications, for example, we set
> > > > > > the bufferCount according to the use-case that the application is
> > > > > > implementing. For example:
> > > > > >
> > > > > > * For preview windows we set bufferCount to 4.
> > > > > > * For video capture we drop fewer frames with a deeper queue so we set it to 6.
> > > > > > * For stills capture we can get by with one frame, though use cases
> > > > > > that capture several stills images for fusion work better if we set
> > > > > > bufferCount to 2 or 3.
> > > > > >
> > > > > > I was wondering how our applications can achieve this behaviour if the
> > > > > > bufferCount field is no longer available.
> > > > >
> > > > > Okay, so the short answer is that the applications, knowing their particular use
> > > > > case, are responsible to provide enough requests to keep the pipeline going. On
> > > > > the pipeline handler side, it's free to use how many internal buffers it wants.
> > > > >
> > > > > So in your case, the pipeline handler could still allocate that same number of
> > > > > internal buffers as you previously did based on bufferCount, but now based
> > > > > solely on the StreamRole set. The application would then allocate and queue
> > > > > how many buffers fits the usage. (Note that before the application would call
> > > > > FrameBufferAllocator::allocate() and it would allocate 'bufferCount' buffers,
> > > > > but now the function takes a count argument so the application is free to choose
> > > > > how many)
> > > > >
> > > > > Now, I guess it would be nice for the application to be able to query what is a
> > > > > good number of buffers to use, for example 6 in the video capture of your use
> > > > > case. At the moment, the only information available is that 1 is the minimum
> > > > > number of buffers required. So the application would have to know that 6 is a
> > > > > good number for video capture. Maybe another property could be introduced later
> > > > > for this recommended amount, but previous discussions suggested this is very use
> > > > > case dependent, so might not make sense.
> > > > >
> > > > > I hope this answers the question. If not, I'm still here :).
> > > > >
> > > > > Thanks,
> > > > > Nícolas
> > > > >
> > > > > >
> > > > > > Thanks!
> > > > > > David
> > > > > >
> > > > > > On Fri, 23 Jul 2021 at 00:29, Nícolas F. R. A. Prado
> > > > > > <nfraprado@collabora.com> wrote:
> > > > > > >
> > > > > > > Now that the number of buffers allocated by the FrameBufferAllocator
> > > > > > > helper is passed through FrameBufferAllocator::allocate() and the
> > > > > > > pipelines no longer use bufferCount for internal buffer or V4L2 buffer
> > > > > > > slots allocation, we no longer need to have bufferCount in the
> > > > > > > StreamConfiguration, so remove it.
> > > > > > >
> > > > > > > Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> > > > > > > ---
> > > > > > >
> > > > > > > No changes in v7
> > > > > > >
> > > > > > > Changes in v6:
> > > > > > > - Removed IPU3_BUFFER_COUNT as it was unused
> > > > > > >
> > > > > > >  include/libcamera/stream.h                         |  2 --
> > > > > > >  src/android/camera_stream.cpp                      |  2 +-
> > > > > > >  src/libcamera/pipeline/ipu3/cio2.cpp               |  1 -
> > > > > > >  src/libcamera/pipeline/ipu3/ipu3.cpp               |  8 --------
> > > > > > >  src/libcamera/pipeline/raspberrypi/raspberrypi.cpp |  6 ------
> > > > > > >  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp      |  2 --
> > > > > > >  src/libcamera/pipeline/simple/converter.cpp        |  3 ---
> > > > > > >  src/libcamera/pipeline/simple/converter.h          |  3 ---
> > > > > > >  src/libcamera/pipeline/simple/simple.cpp           |  5 +----
> > > > > > >  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp       |  3 ---
> > > > > > >  src/libcamera/pipeline/vimc/vimc.cpp               |  3 ---
> > > > > > >  src/libcamera/stream.cpp                           |  9 ++-------
> > > > > > >  src/v4l2/v4l2_camera.cpp                           | 14 ++++++++++----
> > > > > > >  src/v4l2/v4l2_camera.h                             |  5 +++--
> > > > > > >  src/v4l2/v4l2_camera_proxy.cpp                     |  8 +++-----
> > > > > > >  test/camera/buffer_import.cpp                      | 10 +++++++---
> > > > > > >  test/libtest/buffer_source.cpp                     |  4 ++--
> > > > > > >  test/libtest/buffer_source.h                       |  2 +-
> > > > > > >  test/v4l2_videodevice/buffer_cache.cpp             |  4 ++--
> > > > > > >  19 files changed, 32 insertions(+), 62 deletions(-)
> > > > > > >
> > > > > > > diff --git a/include/libcamera/stream.h b/include/libcamera/stream.h
> > > > > > > index 0c55e7164592..b25f0059f2f1 100644
> > > > > > > --- a/include/libcamera/stream.h
> > > > > > > +++ b/include/libcamera/stream.h
> > > > > > > @@ -45,8 +45,6 @@ struct StreamConfiguration {
> > > > > > >         unsigned int stride;
> > > > > > >         unsigned int frameSize;
> > > > > > >
> > > > > > > -       unsigned int bufferCount;
> > > > > > > -
> > > > > > >         Stream *stream() const { return stream_; }
> > > > > > >         void setStream(Stream *stream) { stream_ = stream; }
> > > > > > >         const StreamFormats &formats() const { return formats_; }
> > > > > > > diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
> > > > > > > index b168e3c0c288..0794be409f82 100644
> > > > > > > --- a/src/android/camera_stream.cpp
> > > > > > > +++ b/src/android/camera_stream.cpp
> > > > > > > @@ -94,7 +94,7 @@ int CameraStream::configure()
> > > > > > >                         buffers_.push_back(frameBuffer.get());
> > > > > > >         }
> > > > > > >
> > > > > > > -       camera3Stream_->max_buffers = configuration().bufferCount;
> > > > > > > +       camera3Stream_->max_buffers = bufferCount;
> > > > > > >
> > > > > > >         return 0;
> > > > > > >  }
> > > > > > > diff --git a/src/libcamera/pipeline/ipu3/cio2.cpp b/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > > > > index 1bcd580e251c..0e04e7214489 100644
> > > > > > > --- a/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > > > > +++ b/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > > > > @@ -214,7 +214,6 @@ StreamConfiguration CIO2Device::generateConfiguration(Size size) const
> > > > > > >
> > > > > > >         cfg.size = sensorFormat.size;
> > > > > > >         cfg.pixelFormat = mbusCodesToPixelFormat.at(sensorFormat.mbus_code);
> > > > > > > -       cfg.bufferCount = CIO2_BUFFER_COUNT;
> > > > > > >
> > > > > > >         return cfg;
> > > > > > >  }
> > > > > > > diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > > > index 4efd201c05e5..b223b3f33cd0 100644
> > > > > > > --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > > > +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > > > @@ -38,7 +38,6 @@ namespace libcamera {
> > > > > > >
> > > > > > >  LOG_DEFINE_CATEGORY(IPU3)
> > > > > > >
> > > > > > > -static constexpr unsigned int IPU3_BUFFER_COUNT = 4;
> > > > > > >  static constexpr unsigned int IPU3_MAX_STREAMS = 3;
> > > > > > >  static const Size IMGU_OUTPUT_MIN_SIZE = { 2, 2 };
> > > > > > >  static const Size IMGU_OUTPUT_MAX_SIZE = { 4480, 34004 };
> > > > > > > @@ -295,7 +294,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > > > > > >                         /* Initialize the RAW stream with the CIO2 configuration. */
> > > > > > >                         cfg->size = cio2Configuration_.size;
> > > > > > >                         cfg->pixelFormat = cio2Configuration_.pixelFormat;
> > > > > > > -                       cfg->bufferCount = cio2Configuration_.bufferCount;
> > > > > > >                         cfg->stride = info.stride(cfg->size.width, 0, 64);
> > > > > > >                         cfg->frameSize = info.frameSize(cfg->size, 64);
> > > > > > >                         cfg->setStream(const_cast<Stream *>(&data_->rawStream_));
> > > > > > > @@ -339,7 +337,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > > > > > >                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> > > > > > >
> > > > > > >                         cfg->pixelFormat = formats::NV12;
> > > > > > > -                       cfg->bufferCount = IPU3_BUFFER_COUNT;
> > > > > > >                         cfg->stride = info.stride(cfg->size.width, 0, 1);
> > > > > > >                         cfg->frameSize = info.frameSize(cfg->size, 1);
> > > > > > >
> > > > > > > @@ -407,7 +404,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > > >         Size sensorResolution = data->cio2_.sensor()->resolution();
> > > > > > >         for (const StreamRole role : roles) {
> > > > > > >                 std::map<PixelFormat, std::vector<SizeRange>> streamFormats;
> > > > > > > -               unsigned int bufferCount;
> > > > > > >                 PixelFormat pixelFormat;
> > > > > > >                 Size size;
> > > > > > >
> > > > > > > @@ -428,7 +424,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > > >                         size.height = utils::alignDown(size.height - 1,
> > > > > > >                                                        IMGU_OUTPUT_HEIGHT_MARGIN);
> > > > > > >                         pixelFormat = formats::NV12;
> > > > > > > -                       bufferCount = IPU3_BUFFER_COUNT;
> > > > > > >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> > > > > > >
> > > > > > >                         break;
> > > > > > > @@ -438,7 +433,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > > >                                 data->cio2_.generateConfiguration(sensorResolution);
> > > > > > >                         pixelFormat = cio2Config.pixelFormat;
> > > > > > >                         size = cio2Config.size;
> > > > > > > -                       bufferCount = cio2Config.bufferCount;
> > > > > > >
> > > > > > >                         for (const PixelFormat &format : data->cio2_.formats())
> > > > > > >                                 streamFormats[format] = data->cio2_.sizes();
> > > > > > > @@ -457,7 +451,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > > >                                                .alignedDownTo(IMGU_OUTPUT_WIDTH_ALIGN,
> > > > > > >                                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> > > > > > >                         pixelFormat = formats::NV12;
> > > > > > > -                       bufferCount = IPU3_BUFFER_COUNT;
> > > > > > >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> > > > > > >
> > > > > > >                         break;
> > > > > > > @@ -474,7 +467,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > > >                 StreamConfiguration cfg(formats);
> > > > > > >                 cfg.size = size;
> > > > > > >                 cfg.pixelFormat = pixelFormat;
> > > > > > > -               cfg.bufferCount = bufferCount;
> > > > > > >                 config->addConfiguration(cfg);
> > > > > > >         }
> > > > > > >
> > > > > > > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > > > index 776e0f92aed1..e6fc0425c3ef 100644
> > > > > > > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > > > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > > > @@ -473,7 +473,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > > >         RPiCameraData *data = cameraData(camera);
> > > > > > >         CameraConfiguration *config = new RPiCameraConfiguration(data);
> > > > > > >         V4L2DeviceFormat sensorFormat;
> > > > > > > -       unsigned int bufferCount;
> > > > > > >         PixelFormat pixelFormat;
> > > > > > >         V4L2VideoDevice::Formats fmts;
> > > > > > >         Size size;
> > > > > > > @@ -491,7 +490,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > > >                         sensorFormat = findBestMode(fmts, size);
> > > > > > >                         pixelFormat = sensorFormat.fourcc.toPixelFormat();
> > > > > > >                         ASSERT(pixelFormat.isValid());
> > > > > > > -                       bufferCount = 2;
> > > > > > >                         rawCount++;
> > > > > > >                         break;
> > > > > > >
> > > > > > > @@ -500,7 +498,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > > >                         pixelFormat = formats::NV12;
> > > > > > >                         /* Return the largest sensor resolution. */
> > > > > > >                         size = data->sensor_->resolution();
> > > > > > > -                       bufferCount = 1;
> > > > > > >                         outCount++;
> > > > > > >                         break;
> > > > > > >
> > > > > > > @@ -516,7 +513,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > > >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> > > > > > >                         pixelFormat = formats::YUV420;
> > > > > > >                         size = { 1920, 1080 };
> > > > > > > -                       bufferCount = 4;
> > > > > > >                         outCount++;
> > > > > > >                         break;
> > > > > > >
> > > > > > > @@ -524,7 +520,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > > >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> > > > > > >                         pixelFormat = formats::ARGB8888;
> > > > > > >                         size = { 800, 600 };
> > > > > > > -                       bufferCount = 4;
> > > > > > >                         outCount++;
> > > > > > >                         break;
> > > > > > >
> > > > > > > @@ -554,7 +549,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > > >                 StreamConfiguration cfg(formats);
> > > > > > >                 cfg.size = size;
> > > > > > >                 cfg.pixelFormat = pixelFormat;
> > > > > > > -               cfg.bufferCount = bufferCount;
> > > > > > >                 config->addConfiguration(cfg);
> > > > > > >         }
> > > > > > >
> > > > > > > diff --git a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > > > > index fea330f72886..4961f3971e59 100644
> > > > > > > --- a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > > > > +++ b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > > > > @@ -61,7 +61,6 @@ StreamConfiguration RkISP1Path::generateConfiguration(const Size &resolution)
> > > > > > >         StreamConfiguration cfg(formats);
> > > > > > >         cfg.pixelFormat = formats::NV12;
> > > > > > >         cfg.size = maxResolution;
> > > > > > > -       cfg.bufferCount = RKISP1_BUFFER_COUNT;
> > > > > > >
> > > > > > >         return cfg;
> > > > > > >  }
> > > > > > > @@ -77,7 +76,6 @@ CameraConfiguration::Status RkISP1Path::validate(StreamConfiguration *cfg)
> > > > > > >
> > > > > > >         cfg->size.boundTo(maxResolution_);
> > > > > > >         cfg->size.expandTo(minResolution_);
> > > > > > > -       cfg->bufferCount = RKISP1_BUFFER_COUNT;
> > > > > > >
> > > > > > >         V4L2DeviceFormat format;
> > > > > > >         format.fourcc = video_->toV4L2PixelFormat(cfg->pixelFormat);
> > > > > > > diff --git a/src/libcamera/pipeline/simple/converter.cpp b/src/libcamera/pipeline/simple/converter.cpp
> > > > > > > index b3bcf01483f7..fda417793e80 100644
> > > > > > > --- a/src/libcamera/pipeline/simple/converter.cpp
> > > > > > > +++ b/src/libcamera/pipeline/simple/converter.cpp
> > > > > > > @@ -89,9 +89,6 @@ int SimpleConverter::Stream::configure(const StreamConfiguration &inputCfg,
> > > > > > >                 return -EINVAL;
> > > > > > >         }
> > > > > > >
> > > > > > > -       inputBufferCount_ = inputCfg.bufferCount;
> > > > > > > -       outputBufferCount_ = outputCfg.bufferCount;
> > > > > > > -
> > > > > > >         return 0;
> > > > > > >  }
> > > > > > >
> > > > > > > diff --git a/src/libcamera/pipeline/simple/converter.h b/src/libcamera/pipeline/simple/converter.h
> > > > > > > index 7e1d60674f62..406e63ca2a80 100644
> > > > > > > --- a/src/libcamera/pipeline/simple/converter.h
> > > > > > > +++ b/src/libcamera/pipeline/simple/converter.h
> > > > > > > @@ -87,9 +87,6 @@ private:
> > > > > > >                 SimpleConverter *converter_;
> > > > > > >                 unsigned int index_;
> > > > > > >                 std::unique_ptr<V4L2M2MDevice> m2m_;
> > > > > > > -
> > > > > > > -               unsigned int inputBufferCount_;
> > > > > > > -               unsigned int outputBufferCount_;
> > > > > > >         };
> > > > > > >
> > > > > > >         std::string deviceNode_;
> > > > > > > diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> > > > > > > index a1163eaf8be2..ded04914f610 100644
> > > > > > > --- a/src/libcamera/pipeline/simple/simple.cpp
> > > > > > > +++ b/src/libcamera/pipeline/simple/simple.cpp
> > > > > > > @@ -628,7 +628,7 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> > > > > > >                     cfg.size != pipeConfig_->captureSize)
> > > > > > >                         needConversion_ = true;
> > > > > > >
> > > > > > > -               /* Set the stride, frameSize and bufferCount. */
> > > > > > > +               /* Set the stride and frameSize. */
> > > > > > >                 if (needConversion_) {
> > > > > > >                         std::tie(cfg.stride, cfg.frameSize) =
> > > > > > >                                 converter->strideAndFrameSize(cfg.pixelFormat, cfg.size);
> > > > > > > @@ -646,8 +646,6 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> > > > > > >                         cfg.stride = format.planes[0].bpl;
> > > > > > >                         cfg.frameSize = format.planes[0].size;
> > > > > > >                 }
> > > > > > > -
> > > > > > > -               cfg.bufferCount = 3;
> > > > > > >         }
> > > > > > >
> > > > > > >         return status;
> > > > > > > @@ -770,7 +768,6 @@ int SimplePipelineHandler::configure(Camera *camera, CameraConfiguration *c)
> > > > > > >         inputCfg.pixelFormat = pipeConfig->captureFormat;
> > > > > > >         inputCfg.size = pipeConfig->captureSize;
> > > > > > >         inputCfg.stride = captureFormat.planes[0].bpl;
> > > > > > > -       inputCfg.bufferCount = kNumInternalBuffers;
> > > > > > >
> > > > > > >         return converter_->configure(inputCfg, outputCfgs);
> > > > > > >  }
> > > > > > > diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > > > > index 755949e7a59a..32482300f09a 100644
> > > > > > > --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > > > > +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > > > > @@ -150,8 +150,6 @@ CameraConfiguration::Status UVCCameraConfiguration::validate()
> > > > > > >                 status = Adjusted;
> > > > > > >         }
> > > > > > >
> > > > > > > -       cfg.bufferCount = 4;
> > > > > > > -
> > > > > > >         V4L2DeviceFormat format;
> > > > > > >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> > > > > > >         format.size = cfg.size;
> > > > > > > @@ -193,7 +191,6 @@ CameraConfiguration *PipelineHandlerUVC::generateConfiguration(Camera *camera,
> > > > > > >
> > > > > > >         cfg.pixelFormat = formats.pixelformats().front();
> > > > > > >         cfg.size = formats.sizes(cfg.pixelFormat).back();
> > > > > > > -       cfg.bufferCount = 4;
> > > > > > >
> > > > > > >         config->addConfiguration(cfg);
> > > > > > >
> > > > > > > diff --git a/src/libcamera/pipeline/vimc/vimc.cpp b/src/libcamera/pipeline/vimc/vimc.cpp
> > > > > > > index 24ba743a946c..a698427c4361 100644
> > > > > > > --- a/src/libcamera/pipeline/vimc/vimc.cpp
> > > > > > > +++ b/src/libcamera/pipeline/vimc/vimc.cpp
> > > > > > > @@ -167,8 +167,6 @@ CameraConfiguration::Status VimcCameraConfiguration::validate()
> > > > > > >                 status = Adjusted;
> > > > > > >         }
> > > > > > >
> > > > > > > -       cfg.bufferCount = 4;
> > > > > > > -
> > > > > > >         V4L2DeviceFormat format;
> > > > > > >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> > > > > > >         format.size = cfg.size;
> > > > > > > @@ -224,7 +222,6 @@ CameraConfiguration *PipelineHandlerVimc::generateConfiguration(Camera *camera,
> > > > > > >
> > > > > > >         cfg.pixelFormat = formats::BGR888;
> > > > > > >         cfg.size = { 1920, 1080 };
> > > > > > > -       cfg.bufferCount = 4;
> > > > > > >
> > > > > > >         config->addConfiguration(cfg);
> > > > > > >
> > > > > > > diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
> > > > > > > index b8626775d224..ca507b72b26a 100644
> > > > > > > --- a/src/libcamera/stream.cpp
> > > > > > > +++ b/src/libcamera/stream.cpp
> > > > > > > @@ -280,7 +280,7 @@ SizeRange StreamFormats::range(const PixelFormat &pixelformat) const
> > > > > > >   * handlers provide StreamFormats.
> > > > > > >   */
> > > > > > >  StreamConfiguration::StreamConfiguration()
> > > > > > > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > > > > > > +       : pixelFormat(0), stride(0), frameSize(0),
> > > > > > >           stream_(nullptr)
> > > > > > >  {
> > > > > > >  }
> > > > > > > @@ -289,7 +289,7 @@ StreamConfiguration::StreamConfiguration()
> > > > > > >   * \brief Construct a configuration with stream formats
> > > > > > >   */
> > > > > > >  StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > > > > > > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > > > > > > +       : pixelFormat(0), stride(0), frameSize(0),
> > > > > > >           stream_(nullptr), formats_(formats)
> > > > > > >  {
> > > > > > >  }
> > > > > > > @@ -324,11 +324,6 @@ StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > > > > > >   * validating the configuration with a call to CameraConfiguration::validate().
> > > > > > >   */
> > > > > > >
> > > > > > > -/**
> > > > > > > - * \var StreamConfiguration::bufferCount
> > > > > > > - * \brief Requested number of buffers to allocate for the stream
> > > > > > > - */
> > > > > > > -
> > > > > > >  /**
> > > > > > >   * \fn StreamConfiguration::stream()
> > > > > > >   * \brief Retrieve the stream associated with the configuration
> > > > > > > diff --git a/src/v4l2/v4l2_camera.cpp b/src/v4l2/v4l2_camera.cpp
> > > > > > > index d01eacfa2b84..2ff9affc6388 100644
> > > > > > > --- a/src/v4l2/v4l2_camera.cpp
> > > > > > > +++ b/src/v4l2/v4l2_camera.cpp
> > > > > > > @@ -12,6 +12,8 @@
> > > > > > >
> > > > > > >  #include <libcamera/base/log.h>
> > > > > > >
> > > > > > > +#include <libcamera/property_ids.h>
> > > > > > > +
> > > > > > >  using namespace libcamera;
> > > > > > >
> > > > > > >  LOG_DECLARE_CATEGORY(V4L2Compat)
> > > > > > > @@ -107,14 +109,12 @@ void V4L2Camera::requestComplete(Request *request)
> > > > > > >  }
> > > > > > >
> > > > > > >  int V4L2Camera::configure(StreamConfiguration *streamConfigOut,
> > > > > > > -                         const Size &size, const PixelFormat &pixelformat,
> > > > > > > -                         unsigned int bufferCount)
> > > > > > > +                         const Size &size, const PixelFormat &pixelformat)
> > > > > > >  {
> > > > > > >         StreamConfiguration &streamConfig = config_->at(0);
> > > > > > >         streamConfig.size.width = size.width;
> > > > > > >         streamConfig.size.height = size.height;
> > > > > > >         streamConfig.pixelFormat = pixelformat;
> > > > > > > -       streamConfig.bufferCount = bufferCount;
> > > > > > >         /* \todo memoryType (interval vs external) */
> > > > > > >
> > > > > > >         CameraConfiguration::Status validation = config_->validate();
> > > > > > > @@ -146,7 +146,6 @@ int V4L2Camera::validateConfiguration(const PixelFormat &pixelFormat,
> > > > > > >         StreamConfiguration &cfg = config->at(0);
> > > > > > >         cfg.size = size;
> > > > > > >         cfg.pixelFormat = pixelFormat;
> > > > > > > -       cfg.bufferCount = 1;
> > > > > > >
> > > > > > >         CameraConfiguration::Status validation = config->validate();
> > > > > > >         if (validation == CameraConfiguration::Invalid)
> > > > > > > @@ -299,3 +298,10 @@ bool V4L2Camera::isRunning()
> > > > > > >  {
> > > > > > >         return isRunning_;
> > > > > > >  }
> > > > > > > +
> > > > > > > +unsigned int V4L2Camera::minimumRequests(unsigned int count)
> > > > > > > +{
> > > > > > > +       unsigned int min = camera_->properties().get(properties::MinimumRequests);
> > > > > > > +
> > > > > > > +       return std::max(count, min);
> > > > > > > +}
> > > > > > > diff --git a/src/v4l2/v4l2_camera.h b/src/v4l2/v4l2_camera.h
> > > > > > > index a095f4e27524..4b5618ac12b5 100644
> > > > > > > --- a/src/v4l2/v4l2_camera.h
> > > > > > > +++ b/src/v4l2/v4l2_camera.h
> > > > > > > @@ -45,8 +45,7 @@ public:
> > > > > > >         std::vector<Buffer> completedBuffers();
> > > > > > >
> > > > > > >         int configure(StreamConfiguration *streamConfigOut,
> > > > > > > -                     const Size &size, const PixelFormat &pixelformat,
> > > > > > > -                     unsigned int bufferCount);
> > > > > > > +                     const Size &size, const PixelFormat &pixelformat);
> > > > > > >         int validateConfiguration(const PixelFormat &pixelformat,
> > > > > > >                                   const Size &size,
> > > > > > >                                   StreamConfiguration *streamConfigOut);
> > > > > > > @@ -65,6 +64,8 @@ public:
> > > > > > >
> > > > > > >         bool isRunning();
> > > > > > >
> > > > > > > +       unsigned int minimumRequests(unsigned int count);
> > > > > > > +
> > > > > > >  private:
> > > > > > >         void requestComplete(Request *request);
> > > > > > >
> > > > > > > diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
> > > > > > > index 7682c4bddf90..634ec84e0cbb 100644
> > > > > > > --- a/src/v4l2/v4l2_camera_proxy.cpp
> > > > > > > +++ b/src/v4l2/v4l2_camera_proxy.cpp
> > > > > > > @@ -349,8 +349,7 @@ int V4L2CameraProxy::vidioc_s_fmt(V4L2CameraFile *file, struct v4l2_format *arg)
> > > > > > >         Size size(arg->fmt.pix.width, arg->fmt.pix.height);
> > > > > > >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(arg->fmt.pix.pixelformat);
> > > > > > >         ret = vcam_->configure(&streamConfig_, size,
> > > > > > > -                              PixelFormatInfo::info(v4l2Format).format,
> > > > > > > -                              bufferCount_);
> > > > > > > +                              PixelFormatInfo::info(v4l2Format).format);
> > > > > > >         if (ret < 0)
> > > > > > >                 return -EINVAL;
> > > > > > >
> > > > > > > @@ -491,14 +490,13 @@ int V4L2CameraProxy::vidioc_reqbufs(V4L2CameraFile *file, struct v4l2_requestbuf
> > > > > > >         Size size(v4l2PixFormat_.width, v4l2PixFormat_.height);
> > > > > > >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(v4l2PixFormat_.pixelformat);
> > > > > > >         int ret = vcam_->configure(&streamConfig_, size,
> > > > > > > -                                  PixelFormatInfo::info(v4l2Format).format,
> > > > > > > -                                  arg->count);
> > > > > > > +                                  PixelFormatInfo::info(v4l2Format).format);
> > > > > > >         if (ret < 0)
> > > > > > >                 return -EINVAL;
> > > > > > >
> > > > > > >         setFmtFromConfig(streamConfig_);
> > > > > > >
> > > > > > > -       arg->count = streamConfig_.bufferCount;
> > > > > > > +       arg->count = vcam_->minimumRequests(arg->count);
> > > > > > >         bufferCount_ = arg->count;
> > > > > > >
> > > > > > >         ret = vcam_->allocBuffers(arg->count);
> > > > > > > diff --git a/test/camera/buffer_import.cpp b/test/camera/buffer_import.cpp
> > > > > > > index c504ea09e64b..67ac0ad20e15 100644
> > > > > > > --- a/test/camera/buffer_import.cpp
> > > > > > > +++ b/test/camera/buffer_import.cpp
> > > > > > > @@ -16,6 +16,8 @@
> > > > > > >  #include <libcamera/base/thread.h>
> > > > > > >  #include <libcamera/base/timer.h>
> > > > > > >
> > > > > > > +#include <libcamera/property_ids.h>
> > > > > > > +
> > > > > > >  #include "libcamera/internal/device_enumerator.h"
> > > > > > >  #include "libcamera/internal/media_device.h"
> > > > > > >  #include "libcamera/internal/v4l2_videodevice.h"
> > > > > > > @@ -92,10 +94,12 @@ protected:
> > > > > > >                         return TestFail;
> > > > > > >                 }
> > > > > > >
> > > > > > > +               unsigned int bufferCount = camera_->properties().get(properties::MinimumRequests);
> > > > > > > +
> > > > > > >                 Stream *stream = cfg.stream();
> > > > > > >
> > > > > > >                 BufferSource source;
> > > > > > > -               int ret = source.allocate(cfg);
> > > > > > > +               int ret = source.allocate(cfg, bufferCount);
> > > > > > >                 if (ret != TestPass)
> > > > > > >                         return ret;
> > > > > > >
> > > > > > > @@ -139,10 +143,10 @@ protected:
> > > > > > >                 while (timer.isRunning())
> > > > > > >                         dispatcher->processEvents();
> > > > > > >
> > > > > > > -               if (completeRequestsCount_ < cfg.bufferCount * 2) {
> > > > > > > +               if (completeRequestsCount_ < bufferCount * 2) {
> > > > > > >                         std::cout << "Failed to capture enough frames (got "
> > > > > > >                                   << completeRequestsCount_ << " expected at least "
> > > > > > > -                                 << cfg.bufferCount * 2 << ")" << std::endl;
> > > > > > > +                                 << bufferCount * 2 << ")" << std::endl;
> > > > > > >                         return TestFail;
> > > > > > >                 }
> > > > > > >
> > > > > > > diff --git a/test/libtest/buffer_source.cpp b/test/libtest/buffer_source.cpp
> > > > > > > index 73563f2fc39d..c3d5286a2462 100644
> > > > > > > --- a/test/libtest/buffer_source.cpp
> > > > > > > +++ b/test/libtest/buffer_source.cpp
> > > > > > > @@ -24,7 +24,7 @@ BufferSource::~BufferSource()
> > > > > > >                 media_->release();
> > > > > > >  }
> > > > > > >
> > > > > > > -int BufferSource::allocate(const StreamConfiguration &config)
> > > > > > > +int BufferSource::allocate(const StreamConfiguration &config, unsigned int count)
> > > > > > >  {
> > > > > > >         /* Locate and open the video device. */
> > > > > > >         std::string videoDeviceName = "vivid-000-vid-out";
> > > > > > > @@ -77,7 +77,7 @@ int BufferSource::allocate(const StreamConfiguration &config)
> > > > > > >                 return TestFail;
> > > > > > >         }
> > > > > > >
> > > > > > > -       if (video->allocateBuffers(config.bufferCount, &buffers_) < 0) {
> > > > > > > +       if (video->allocateBuffers(count, &buffers_) < 0) {
> > > > > > >                 std::cout << "Failed to allocate buffers" << std::endl;
> > > > > > >                 return TestFail;
> > > > > > >         }
> > > > > > > diff --git a/test/libtest/buffer_source.h b/test/libtest/buffer_source.h
> > > > > > > index 14b4770e8d8a..6a18e269a575 100644
> > > > > > > --- a/test/libtest/buffer_source.h
> > > > > > > +++ b/test/libtest/buffer_source.h
> > > > > > > @@ -20,7 +20,7 @@ public:
> > > > > > >         BufferSource();
> > > > > > >         ~BufferSource();
> > > > > > >
> > > > > > > -       int allocate(const StreamConfiguration &config);
> > > > > > > +       int allocate(const StreamConfiguration &config, unsigned int count);
> > > > > > >         const std::vector<std::unique_ptr<FrameBuffer>> &buffers();
> > > > > > >
> > > > > > >  private:
> > > > > > > diff --git a/test/v4l2_videodevice/buffer_cache.cpp b/test/v4l2_videodevice/buffer_cache.cpp
> > > > > > > index b3f2bec11783..07fddfd2617c 100644
> > > > > > > --- a/test/v4l2_videodevice/buffer_cache.cpp
> > > > > > > +++ b/test/v4l2_videodevice/buffer_cache.cpp
> > > > > > > @@ -10,6 +10,7 @@
> > > > > > >  #include <vector>
> > > > > > >
> > > > > > >  #include <libcamera/formats.h>
> > > > > > > +#include <libcamera/property_ids.h>
> > > > > > >  #include <libcamera/stream.h>
> > > > > > >
> > > > > > >  #include "buffer_source.h"
> > > > > > > @@ -145,10 +146,9 @@ public:
> > > > > > >                 StreamConfiguration cfg;
> > > > > > >                 cfg.pixelFormat = formats::YUYV;
> > > > > > >                 cfg.size = Size(600, 800);
> > > > > > > -               cfg.bufferCount = numBuffers;
> > > > > > >
> > > > > > >                 BufferSource source;
> > > > > > > -               int ret = source.allocate(cfg);
> > > > > > > +               int ret = source.allocate(cfg, numBuffers);
> > > > > > >                 if (ret != TestPass)
> > > > > > >                         return ret;
> > > > > > >
> > > > > > > --
> > > > > > > 2.32.0
> > > > > > >

Hello everybody,

Sorry for replying late to this mail thread.

On Thu, Jul 29, 2021 at 05:03:24PM +0100, David Plowman wrote:
> Ah, OK, that sounds straightforward, then. Thanks for the explanation!

It sounds like the issue is solved :-) I would however like to point out
a detail that may affect performance.

We have a cache in the V4L2VideoDevice that tries to keep the
association between a V4L2 buffer slot and a dma-buf constant. This is
important as if a different dma-buf is passed to a QBUF ioctl call to a
buffer slot, V4L2 will unmap the previous dma-buf and map the new one,
which is an expensive operation. This mechanism can only work if you
allocate at least as many buffers slots as the number of different
dma-bufs an application may queue. If the application constantly queue
different buffers there's nothing that can be done about it and new
mappings will have to be created all the time, but in most cases the
application will cycle through the same buffers.

There is, in this patch series, no mechanism to inform the pipeline
handler about the maximum number of different dma-bufs that will be used
for a given stream. V4L2 buffer slots are cheap, so one option is to
simply over-allocate when calling VIDIOC_REQBUFS. If this causes issues,
then we'll have to add a way for applications to specify how many
different buffers they expect to use.

> On Thu, 29 Jul 2021 at 15:38, Nícolas F. R. A. Prado wrote:
> > On Thu, Jul 29, 2021 at 11:00:33AM +0100, David Plowman wrote:
> > > Hi again
> > >
> > > I thought that perhaps I could explain in more detail why I think
> > > applications need to be able to set (or influence) the buffer count
> > > and not leave it to the pipeline handler. My use-case is as follows.
> > >
> > > I'm running some standard sort of application such as video recording
> > > for which there are maybe 4 buffers allocated. Now, I also want to do
> > > some image analysis that perhaps causes me to change something about
> > > the recording (maybe change camera settings, or even stop the
> > > recording). But this image analysis task is relatively slow.
> > >
> > > One option is to copy the camera frames so that I can return the
> > > buffers in the request back to the camera. But copying images is
> > > generally undesirable. Instead I'd prefer to hold on to the buffer
> > > only now my camera pipeline is effectively working with only 3
> > > buffers, which is not enough. When I eventually finish with the buffer
> > > I will return it, and then grab the next one to keep again!
> >
> > Ohh, I see. Sorry, I got a bit confused there, but this is not a problem at all.
> > If you want the pipeline to work with extra requests/buffers, you just supply
> > more to it :). Going back to your code snippet, this would be the change:
> >
> >     configuration_ = camera_->generateConfiguration({ StreamRole::StillCapture });
> > -   configuration_->at(0).bufferCount = <value I have determined>;
> >     camera_->configure(configuration_.get());
> >     allocator_ = new FrameBufferAllocator(camera_);
> >     Stream *stream = configuration_->at(0).stream();
> > -   allocator_->allocate(stream);
> > +   allocator_->allocate(stream, <value I have determined>);
> >     // now allocator_->buffers(stream) has the buffers I want!
> >
> > So, basically, you don't need to set bufferCount anymore, and instead you
> > allocate as many buffers as you need to give the pipeline handler by directly
> > passing the number to FrameBufferAllocator. In your case you want to allocate an
> > extra buffer to compensate for the one you'll be keeping.
> >
> > It was already possible to supply the pipeline handler with how many
> > buffers you wanted, but previously you had to allocate them elsewhere, while now
> > you can allocate with the FrameBufferAllocator since it accepts the count
> > argument. (Actually for the raspberry pipeline it was already possible to do
> > this implicitly through bufferCount as you did, but not with the other
> > pipelines).
> >
> > What I meant wasn't possible to change is how many internal buffers for metadata
> > and parameters the pipeline uses together with the IPA. And also how many V4L2
> > buffer slots are created to queue the requests into. But all of this is indeed
> > only relevant to the pipeline handler, so an application shouldn't care about
> > it. All of this, together with how many buffers the application would allocate,
> > was previously grouped on bufferCount. With its deletion, however, they are
> > getting split up.
> >
> > I hope I got it right this time :).
> >
> > > So at the very least, the application needs to be able to say "please
> > > allocate <n> more buffers than you thought you needed". Does that make
> > > sense? Will this be possible in the new scheme?
> > >
> > > On Fri, 23 Jul 2021 at 22:08, Nícolas F. R. A. Prado wrote:
> > > > On Fri, Jul 23, 2021 at 04:53:55PM +0100, David Plowman wrote:
> > > > > Hi Nicolas
> > > > >
> > > > > Thanks for the explanations. I'm still not sure I entirely understand
> > > > > so perhaps a quick look at how I would have to change my application
> > > > > code might help? Here's what I have now (I've removed any
> > > > > "unimportant" bits!):
> > > > >
> > > > > configuration_ = camera_->generateConfiguration({ StreamRole::StillCapture });
> > > > > configuration_->at(0).bufferCount = <value I have determined>;
> > > > > camera_->configure(configuration_.get());
> > > > > allocator_ = new FrameBufferAllocator(camera_);
> > > > > Stream *stream = configuration_->at(0).stream();
> > > > > allocator_->allocate(stream);
> > > > > // now allocator_->buffers(stream) has the buffers I want!
> > > > >
> > > > > I guess one thing to note is that the bufferCount value varies with
> > > > > more than just the StreamRole, and I don't in general trust the
> > > > > pipeline handler to "know" what I want. Will this still be possible?
> > > >
> > > > Oh I see... No, this won't be possible after we drop bufferCount. The
> > > > pipeline handler will decide for itself how many buffers to allocate internally,
> > > > possibly using the StreamRole as a hint.
> > > >
> > > > I wasn't aware this could impact an application, since all the other pipeline
> > > > handlers actually ignore when bufferCount is set by the application, overriding
> > > > it when the configuration is validated. But now I'm noticing the raspberrypi
> > > > pipeline actually uses it.
> > > >
> > > > Some context: This series actually began with me making
> > > > FrameBufferAllocator::allocate() receive a count argument instead of using the
> > > > value of bufferCount. But since Laurent mentioned that bufferCount was going
> > > > away eventually anyway I ended up removing it as well as part of this series.
> > > >
> > > > I do understand how being able to specify a bufferCount value that suits your
> > > > specific usecase is useful, though... Laurent, what's your take on this? :)
> > > >
> > > > > On Fri, 23 Jul 2021 at 14:10, Nícolas F. R. A. Prado wrote:
> > > > > >
> > > > > > Hi David,
> > > > > >
> > > > > > On Fri, Jul 23, 2021 at 09:42:56AM +0100, David Plowman wrote:
> > > > > > > Hi Nicolas
> > > > > > >
> > > > > > > Thanks very much for all this work! I was wondering if I could ask a
> > > > > > > little more about this patch. In our applications, for example, we set
> > > > > > > the bufferCount according to the use-case that the application is
> > > > > > > implementing. For example:
> > > > > > >
> > > > > > > * For preview windows we set bufferCount to 4.
> > > > > > > * For video capture we drop fewer frames with a deeper queue so we set it to 6.
> > > > > > > * For stills capture we can get by with one frame, though use cases
> > > > > > > that capture several stills images for fusion work better if we set
> > > > > > > bufferCount to 2 or 3.
> > > > > > >
> > > > > > > I was wondering how our applications can achieve this behaviour if the
> > > > > > > bufferCount field is no longer available.
> > > > > >
> > > > > > Okay, so the short answer is that the applications, knowing their particular use
> > > > > > case, are responsible to provide enough requests to keep the pipeline going. On
> > > > > > the pipeline handler side, it's free to use how many internal buffers it wants.
> > > > > >
> > > > > > So in your case, the pipeline handler could still allocate that same number of
> > > > > > internal buffers as you previously did based on bufferCount, but now based
> > > > > > solely on the StreamRole set. The application would then allocate and queue
> > > > > > how many buffers fits the usage. (Note that before the application would call
> > > > > > FrameBufferAllocator::allocate() and it would allocate 'bufferCount' buffers,
> > > > > > but now the function takes a count argument so the application is free to choose
> > > > > > how many)
> > > > > >
> > > > > > Now, I guess it would be nice for the application to be able to query what is a
> > > > > > good number of buffers to use, for example 6 in the video capture of your use
> > > > > > case. At the moment, the only information available is that 1 is the minimum
> > > > > > number of buffers required. So the application would have to know that 6 is a
> > > > > > good number for video capture. Maybe another property could be introduced later
> > > > > > for this recommended amount, but previous discussions suggested this is very use
> > > > > > case dependent, so might not make sense.
> > > > > >
> > > > > > I hope this answers the question. If not, I'm still here :).
> > > > > >
> > > > > > Thanks,
> > > > > > Nícolas
> > > > > >
> > > > > > >
> > > > > > > Thanks!
> > > > > > > David
> > > > > > >
> > > > > > > On Fri, 23 Jul 2021 at 00:29, Nícolas F. R. A. Prado
> > > > > > > <nfraprado@collabora.com> wrote:
> > > > > > > >
> > > > > > > > Now that the number of buffers allocated by the FrameBufferAllocator
> > > > > > > > helper is passed through FrameBufferAllocator::allocate() and the
> > > > > > > > pipelines no longer use bufferCount for internal buffer or V4L2 buffer
> > > > > > > > slots allocation, we no longer need to have bufferCount in the
> > > > > > > > StreamConfiguration, so remove it.
> > > > > > > >
> > > > > > > > Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> > > > > > > > ---
> > > > > > > >
> > > > > > > > No changes in v7
> > > > > > > >
> > > > > > > > Changes in v6:
> > > > > > > > - Removed IPU3_BUFFER_COUNT as it was unused
> > > > > > > >
> > > > > > > >  include/libcamera/stream.h                         |  2 --
> > > > > > > >  src/android/camera_stream.cpp                      |  2 +-
> > > > > > > >  src/libcamera/pipeline/ipu3/cio2.cpp               |  1 -
> > > > > > > >  src/libcamera/pipeline/ipu3/ipu3.cpp               |  8 --------
> > > > > > > >  src/libcamera/pipeline/raspberrypi/raspberrypi.cpp |  6 ------
> > > > > > > >  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp      |  2 --
> > > > > > > >  src/libcamera/pipeline/simple/converter.cpp        |  3 ---
> > > > > > > >  src/libcamera/pipeline/simple/converter.h          |  3 ---
> > > > > > > >  src/libcamera/pipeline/simple/simple.cpp           |  5 +----
> > > > > > > >  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp       |  3 ---
> > > > > > > >  src/libcamera/pipeline/vimc/vimc.cpp               |  3 ---
> > > > > > > >  src/libcamera/stream.cpp                           |  9 ++-------
> > > > > > > >  src/v4l2/v4l2_camera.cpp                           | 14 ++++++++++----
> > > > > > > >  src/v4l2/v4l2_camera.h                             |  5 +++--
> > > > > > > >  src/v4l2/v4l2_camera_proxy.cpp                     |  8 +++-----
> > > > > > > >  test/camera/buffer_import.cpp                      | 10 +++++++---
> > > > > > > >  test/libtest/buffer_source.cpp                     |  4 ++--
> > > > > > > >  test/libtest/buffer_source.h                       |  2 +-
> > > > > > > >  test/v4l2_videodevice/buffer_cache.cpp             |  4 ++--
> > > > > > > >  19 files changed, 32 insertions(+), 62 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/include/libcamera/stream.h b/include/libcamera/stream.h
> > > > > > > > index 0c55e7164592..b25f0059f2f1 100644
> > > > > > > > --- a/include/libcamera/stream.h
> > > > > > > > +++ b/include/libcamera/stream.h
> > > > > > > > @@ -45,8 +45,6 @@ struct StreamConfiguration {
> > > > > > > >         unsigned int stride;
> > > > > > > >         unsigned int frameSize;
> > > > > > > >
> > > > > > > > -       unsigned int bufferCount;
> > > > > > > > -
> > > > > > > >         Stream *stream() const { return stream_; }
> > > > > > > >         void setStream(Stream *stream) { stream_ = stream; }
> > > > > > > >         const StreamFormats &formats() const { return formats_; }
> > > > > > > > diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
> > > > > > > > index b168e3c0c288..0794be409f82 100644
> > > > > > > > --- a/src/android/camera_stream.cpp
> > > > > > > > +++ b/src/android/camera_stream.cpp
> > > > > > > > @@ -94,7 +94,7 @@ int CameraStream::configure()
> > > > > > > >                         buffers_.push_back(frameBuffer.get());
> > > > > > > >         }
> > > > > > > >
> > > > > > > > -       camera3Stream_->max_buffers = configuration().bufferCount;
> > > > > > > > +       camera3Stream_->max_buffers = bufferCount;
> > > > > > > >
> > > > > > > >         return 0;
> > > > > > > >  }
> > > > > > > > diff --git a/src/libcamera/pipeline/ipu3/cio2.cpp b/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > > > > > index 1bcd580e251c..0e04e7214489 100644
> > > > > > > > --- a/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > > > > > +++ b/src/libcamera/pipeline/ipu3/cio2.cpp
> > > > > > > > @@ -214,7 +214,6 @@ StreamConfiguration CIO2Device::generateConfiguration(Size size) const
> > > > > > > >
> > > > > > > >         cfg.size = sensorFormat.size;
> > > > > > > >         cfg.pixelFormat = mbusCodesToPixelFormat.at(sensorFormat.mbus_code);
> > > > > > > > -       cfg.bufferCount = CIO2_BUFFER_COUNT;
> > > > > > > >
> > > > > > > >         return cfg;
> > > > > > > >  }
> > > > > > > > diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > > > > index 4efd201c05e5..b223b3f33cd0 100644
> > > > > > > > --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > > > > +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> > > > > > > > @@ -38,7 +38,6 @@ namespace libcamera {
> > > > > > > >
> > > > > > > >  LOG_DEFINE_CATEGORY(IPU3)
> > > > > > > >
> > > > > > > > -static constexpr unsigned int IPU3_BUFFER_COUNT = 4;
> > > > > > > >  static constexpr unsigned int IPU3_MAX_STREAMS = 3;
> > > > > > > >  static const Size IMGU_OUTPUT_MIN_SIZE = { 2, 2 };
> > > > > > > >  static const Size IMGU_OUTPUT_MAX_SIZE = { 4480, 34004 };
> > > > > > > > @@ -295,7 +294,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > > > > > > >                         /* Initialize the RAW stream with the CIO2 configuration. */
> > > > > > > >                         cfg->size = cio2Configuration_.size;
> > > > > > > >                         cfg->pixelFormat = cio2Configuration_.pixelFormat;
> > > > > > > > -                       cfg->bufferCount = cio2Configuration_.bufferCount;
> > > > > > > >                         cfg->stride = info.stride(cfg->size.width, 0, 64);
> > > > > > > >                         cfg->frameSize = info.frameSize(cfg->size, 64);
> > > > > > > >                         cfg->setStream(const_cast<Stream *>(&data_->rawStream_));
> > > > > > > > @@ -339,7 +337,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
> > > > > > > >                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> > > > > > > >
> > > > > > > >                         cfg->pixelFormat = formats::NV12;
> > > > > > > > -                       cfg->bufferCount = IPU3_BUFFER_COUNT;
> > > > > > > >                         cfg->stride = info.stride(cfg->size.width, 0, 1);
> > > > > > > >                         cfg->frameSize = info.frameSize(cfg->size, 1);
> > > > > > > >
> > > > > > > > @@ -407,7 +404,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > > > >         Size sensorResolution = data->cio2_.sensor()->resolution();
> > > > > > > >         for (const StreamRole role : roles) {
> > > > > > > >                 std::map<PixelFormat, std::vector<SizeRange>> streamFormats;
> > > > > > > > -               unsigned int bufferCount;
> > > > > > > >                 PixelFormat pixelFormat;
> > > > > > > >                 Size size;
> > > > > > > >
> > > > > > > > @@ -428,7 +424,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > > > >                         size.height = utils::alignDown(size.height - 1,
> > > > > > > >                                                        IMGU_OUTPUT_HEIGHT_MARGIN);
> > > > > > > >                         pixelFormat = formats::NV12;
> > > > > > > > -                       bufferCount = IPU3_BUFFER_COUNT;
> > > > > > > >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> > > > > > > >
> > > > > > > >                         break;
> > > > > > > > @@ -438,7 +433,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > > > >                                 data->cio2_.generateConfiguration(sensorResolution);
> > > > > > > >                         pixelFormat = cio2Config.pixelFormat;
> > > > > > > >                         size = cio2Config.size;
> > > > > > > > -                       bufferCount = cio2Config.bufferCount;
> > > > > > > >
> > > > > > > >                         for (const PixelFormat &format : data->cio2_.formats())
> > > > > > > >                                 streamFormats[format] = data->cio2_.sizes();
> > > > > > > > @@ -457,7 +451,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > > > >                                                .alignedDownTo(IMGU_OUTPUT_WIDTH_ALIGN,
> > > > > > > >                                                               IMGU_OUTPUT_HEIGHT_ALIGN);
> > > > > > > >                         pixelFormat = formats::NV12;
> > > > > > > > -                       bufferCount = IPU3_BUFFER_COUNT;
> > > > > > > >                         streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
> > > > > > > >
> > > > > > > >                         break;
> > > > > > > > @@ -474,7 +467,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
> > > > > > > >                 StreamConfiguration cfg(formats);
> > > > > > > >                 cfg.size = size;
> > > > > > > >                 cfg.pixelFormat = pixelFormat;
> > > > > > > > -               cfg.bufferCount = bufferCount;
> > > > > > > >                 config->addConfiguration(cfg);
> > > > > > > >         }
> > > > > > > >
> > > > > > > > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > > > > index 776e0f92aed1..e6fc0425c3ef 100644
> > > > > > > > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > > > > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > > > > > > > @@ -473,7 +473,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > > > >         RPiCameraData *data = cameraData(camera);
> > > > > > > >         CameraConfiguration *config = new RPiCameraConfiguration(data);
> > > > > > > >         V4L2DeviceFormat sensorFormat;
> > > > > > > > -       unsigned int bufferCount;
> > > > > > > >         PixelFormat pixelFormat;
> > > > > > > >         V4L2VideoDevice::Formats fmts;
> > > > > > > >         Size size;
> > > > > > > > @@ -491,7 +490,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > > > >                         sensorFormat = findBestMode(fmts, size);
> > > > > > > >                         pixelFormat = sensorFormat.fourcc.toPixelFormat();
> > > > > > > >                         ASSERT(pixelFormat.isValid());
> > > > > > > > -                       bufferCount = 2;
> > > > > > > >                         rawCount++;
> > > > > > > >                         break;
> > > > > > > >
> > > > > > > > @@ -500,7 +498,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > > > >                         pixelFormat = formats::NV12;
> > > > > > > >                         /* Return the largest sensor resolution. */
> > > > > > > >                         size = data->sensor_->resolution();
> > > > > > > > -                       bufferCount = 1;
> > > > > > > >                         outCount++;
> > > > > > > >                         break;
> > > > > > > >
> > > > > > > > @@ -516,7 +513,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > > > >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> > > > > > > >                         pixelFormat = formats::YUV420;
> > > > > > > >                         size = { 1920, 1080 };
> > > > > > > > -                       bufferCount = 4;
> > > > > > > >                         outCount++;
> > > > > > > >                         break;
> > > > > > > >
> > > > > > > > @@ -524,7 +520,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > > > >                         fmts = data->isp_[Isp::Output0].dev()->formats();
> > > > > > > >                         pixelFormat = formats::ARGB8888;
> > > > > > > >                         size = { 800, 600 };
> > > > > > > > -                       bufferCount = 4;
> > > > > > > >                         outCount++;
> > > > > > > >                         break;
> > > > > > > >
> > > > > > > > @@ -554,7 +549,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
> > > > > > > >                 StreamConfiguration cfg(formats);
> > > > > > > >                 cfg.size = size;
> > > > > > > >                 cfg.pixelFormat = pixelFormat;
> > > > > > > > -               cfg.bufferCount = bufferCount;
> > > > > > > >                 config->addConfiguration(cfg);
> > > > > > > >         }
> > > > > > > >
> > > > > > > > diff --git a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > > > > > index fea330f72886..4961f3971e59 100644
> > > > > > > > --- a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > > > > > +++ b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> > > > > > > > @@ -61,7 +61,6 @@ StreamConfiguration RkISP1Path::generateConfiguration(const Size &resolution)
> > > > > > > >         StreamConfiguration cfg(formats);
> > > > > > > >         cfg.pixelFormat = formats::NV12;
> > > > > > > >         cfg.size = maxResolution;
> > > > > > > > -       cfg.bufferCount = RKISP1_BUFFER_COUNT;
> > > > > > > >
> > > > > > > >         return cfg;
> > > > > > > >  }
> > > > > > > > @@ -77,7 +76,6 @@ CameraConfiguration::Status RkISP1Path::validate(StreamConfiguration *cfg)
> > > > > > > >
> > > > > > > >         cfg->size.boundTo(maxResolution_);
> > > > > > > >         cfg->size.expandTo(minResolution_);
> > > > > > > > -       cfg->bufferCount = RKISP1_BUFFER_COUNT;
> > > > > > > >
> > > > > > > >         V4L2DeviceFormat format;
> > > > > > > >         format.fourcc = video_->toV4L2PixelFormat(cfg->pixelFormat);
> > > > > > > > diff --git a/src/libcamera/pipeline/simple/converter.cpp b/src/libcamera/pipeline/simple/converter.cpp
> > > > > > > > index b3bcf01483f7..fda417793e80 100644
> > > > > > > > --- a/src/libcamera/pipeline/simple/converter.cpp
> > > > > > > > +++ b/src/libcamera/pipeline/simple/converter.cpp
> > > > > > > > @@ -89,9 +89,6 @@ int SimpleConverter::Stream::configure(const StreamConfiguration &inputCfg,
> > > > > > > >                 return -EINVAL;
> > > > > > > >         }
> > > > > > > >
> > > > > > > > -       inputBufferCount_ = inputCfg.bufferCount;
> > > > > > > > -       outputBufferCount_ = outputCfg.bufferCount;
> > > > > > > > -
> > > > > > > >         return 0;
> > > > > > > >  }
> > > > > > > >
> > > > > > > > diff --git a/src/libcamera/pipeline/simple/converter.h b/src/libcamera/pipeline/simple/converter.h
> > > > > > > > index 7e1d60674f62..406e63ca2a80 100644
> > > > > > > > --- a/src/libcamera/pipeline/simple/converter.h
> > > > > > > > +++ b/src/libcamera/pipeline/simple/converter.h
> > > > > > > > @@ -87,9 +87,6 @@ private:
> > > > > > > >                 SimpleConverter *converter_;
> > > > > > > >                 unsigned int index_;
> > > > > > > >                 std::unique_ptr<V4L2M2MDevice> m2m_;
> > > > > > > > -
> > > > > > > > -               unsigned int inputBufferCount_;
> > > > > > > > -               unsigned int outputBufferCount_;
> > > > > > > >         };
> > > > > > > >
> > > > > > > >         std::string deviceNode_;
> > > > > > > > diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> > > > > > > > index a1163eaf8be2..ded04914f610 100644
> > > > > > > > --- a/src/libcamera/pipeline/simple/simple.cpp
> > > > > > > > +++ b/src/libcamera/pipeline/simple/simple.cpp
> > > > > > > > @@ -628,7 +628,7 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> > > > > > > >                     cfg.size != pipeConfig_->captureSize)
> > > > > > > >                         needConversion_ = true;
> > > > > > > >
> > > > > > > > -               /* Set the stride, frameSize and bufferCount. */
> > > > > > > > +               /* Set the stride and frameSize. */
> > > > > > > >                 if (needConversion_) {
> > > > > > > >                         std::tie(cfg.stride, cfg.frameSize) =
> > > > > > > >                                 converter->strideAndFrameSize(cfg.pixelFormat, cfg.size);
> > > > > > > > @@ -646,8 +646,6 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
> > > > > > > >                         cfg.stride = format.planes[0].bpl;
> > > > > > > >                         cfg.frameSize = format.planes[0].size;
> > > > > > > >                 }
> > > > > > > > -
> > > > > > > > -               cfg.bufferCount = 3;
> > > > > > > >         }
> > > > > > > >
> > > > > > > >         return status;
> > > > > > > > @@ -770,7 +768,6 @@ int SimplePipelineHandler::configure(Camera *camera, CameraConfiguration *c)
> > > > > > > >         inputCfg.pixelFormat = pipeConfig->captureFormat;
> > > > > > > >         inputCfg.size = pipeConfig->captureSize;
> > > > > > > >         inputCfg.stride = captureFormat.planes[0].bpl;
> > > > > > > > -       inputCfg.bufferCount = kNumInternalBuffers;
> > > > > > > >
> > > > > > > >         return converter_->configure(inputCfg, outputCfgs);
> > > > > > > >  }
> > > > > > > > diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > > > > > index 755949e7a59a..32482300f09a 100644
> > > > > > > > --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > > > > > +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > > > > > > @@ -150,8 +150,6 @@ CameraConfiguration::Status UVCCameraConfiguration::validate()
> > > > > > > >                 status = Adjusted;
> > > > > > > >         }
> > > > > > > >
> > > > > > > > -       cfg.bufferCount = 4;
> > > > > > > > -
> > > > > > > >         V4L2DeviceFormat format;
> > > > > > > >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> > > > > > > >         format.size = cfg.size;
> > > > > > > > @@ -193,7 +191,6 @@ CameraConfiguration *PipelineHandlerUVC::generateConfiguration(Camera *camera,
> > > > > > > >
> > > > > > > >         cfg.pixelFormat = formats.pixelformats().front();
> > > > > > > >         cfg.size = formats.sizes(cfg.pixelFormat).back();
> > > > > > > > -       cfg.bufferCount = 4;
> > > > > > > >
> > > > > > > >         config->addConfiguration(cfg);
> > > > > > > >
> > > > > > > > diff --git a/src/libcamera/pipeline/vimc/vimc.cpp b/src/libcamera/pipeline/vimc/vimc.cpp
> > > > > > > > index 24ba743a946c..a698427c4361 100644
> > > > > > > > --- a/src/libcamera/pipeline/vimc/vimc.cpp
> > > > > > > > +++ b/src/libcamera/pipeline/vimc/vimc.cpp
> > > > > > > > @@ -167,8 +167,6 @@ CameraConfiguration::Status VimcCameraConfiguration::validate()
> > > > > > > >                 status = Adjusted;
> > > > > > > >         }
> > > > > > > >
> > > > > > > > -       cfg.bufferCount = 4;
> > > > > > > > -
> > > > > > > >         V4L2DeviceFormat format;
> > > > > > > >         format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
> > > > > > > >         format.size = cfg.size;
> > > > > > > > @@ -224,7 +222,6 @@ CameraConfiguration *PipelineHandlerVimc::generateConfiguration(Camera *camera,
> > > > > > > >
> > > > > > > >         cfg.pixelFormat = formats::BGR888;
> > > > > > > >         cfg.size = { 1920, 1080 };
> > > > > > > > -       cfg.bufferCount = 4;
> > > > > > > >
> > > > > > > >         config->addConfiguration(cfg);
> > > > > > > >
> > > > > > > > diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
> > > > > > > > index b8626775d224..ca507b72b26a 100644
> > > > > > > > --- a/src/libcamera/stream.cpp
> > > > > > > > +++ b/src/libcamera/stream.cpp
> > > > > > > > @@ -280,7 +280,7 @@ SizeRange StreamFormats::range(const PixelFormat &pixelformat) const
> > > > > > > >   * handlers provide StreamFormats.
> > > > > > > >   */
> > > > > > > >  StreamConfiguration::StreamConfiguration()
> > > > > > > > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > > > > > > > +       : pixelFormat(0), stride(0), frameSize(0),
> > > > > > > >           stream_(nullptr)
> > > > > > > >  {
> > > > > > > >  }
> > > > > > > > @@ -289,7 +289,7 @@ StreamConfiguration::StreamConfiguration()
> > > > > > > >   * \brief Construct a configuration with stream formats
> > > > > > > >   */
> > > > > > > >  StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > > > > > > > -       : pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> > > > > > > > +       : pixelFormat(0), stride(0), frameSize(0),
> > > > > > > >           stream_(nullptr), formats_(formats)
> > > > > > > >  {
> > > > > > > >  }
> > > > > > > > @@ -324,11 +324,6 @@ StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> > > > > > > >   * validating the configuration with a call to CameraConfiguration::validate().
> > > > > > > >   */
> > > > > > > >
> > > > > > > > -/**
> > > > > > > > - * \var StreamConfiguration::bufferCount
> > > > > > > > - * \brief Requested number of buffers to allocate for the stream
> > > > > > > > - */
> > > > > > > > -
> > > > > > > >  /**
> > > > > > > >   * \fn StreamConfiguration::stream()
> > > > > > > >   * \brief Retrieve the stream associated with the configuration
> > > > > > > > diff --git a/src/v4l2/v4l2_camera.cpp b/src/v4l2/v4l2_camera.cpp
> > > > > > > > index d01eacfa2b84..2ff9affc6388 100644
> > > > > > > > --- a/src/v4l2/v4l2_camera.cpp
> > > > > > > > +++ b/src/v4l2/v4l2_camera.cpp
> > > > > > > > @@ -12,6 +12,8 @@
> > > > > > > >
> > > > > > > >  #include <libcamera/base/log.h>
> > > > > > > >
> > > > > > > > +#include <libcamera/property_ids.h>
> > > > > > > > +
> > > > > > > >  using namespace libcamera;
> > > > > > > >
> > > > > > > >  LOG_DECLARE_CATEGORY(V4L2Compat)
> > > > > > > > @@ -107,14 +109,12 @@ void V4L2Camera::requestComplete(Request *request)
> > > > > > > >  }
> > > > > > > >
> > > > > > > >  int V4L2Camera::configure(StreamConfiguration *streamConfigOut,
> > > > > > > > -                         const Size &size, const PixelFormat &pixelformat,
> > > > > > > > -                         unsigned int bufferCount)
> > > > > > > > +                         const Size &size, const PixelFormat &pixelformat)
> > > > > > > >  {
> > > > > > > >         StreamConfiguration &streamConfig = config_->at(0);
> > > > > > > >         streamConfig.size.width = size.width;
> > > > > > > >         streamConfig.size.height = size.height;
> > > > > > > >         streamConfig.pixelFormat = pixelformat;
> > > > > > > > -       streamConfig.bufferCount = bufferCount;
> > > > > > > >         /* \todo memoryType (interval vs external) */
> > > > > > > >
> > > > > > > >         CameraConfiguration::Status validation = config_->validate();
> > > > > > > > @@ -146,7 +146,6 @@ int V4L2Camera::validateConfiguration(const PixelFormat &pixelFormat,
> > > > > > > >         StreamConfiguration &cfg = config->at(0);
> > > > > > > >         cfg.size = size;
> > > > > > > >         cfg.pixelFormat = pixelFormat;
> > > > > > > > -       cfg.bufferCount = 1;
> > > > > > > >
> > > > > > > >         CameraConfiguration::Status validation = config->validate();
> > > > > > > >         if (validation == CameraConfiguration::Invalid)
> > > > > > > > @@ -299,3 +298,10 @@ bool V4L2Camera::isRunning()
> > > > > > > >  {
> > > > > > > >         return isRunning_;
> > > > > > > >  }
> > > > > > > > +
> > > > > > > > +unsigned int V4L2Camera::minimumRequests(unsigned int count)
> > > > > > > > +{
> > > > > > > > +       unsigned int min = camera_->properties().get(properties::MinimumRequests);
> > > > > > > > +
> > > > > > > > +       return std::max(count, min);
> > > > > > > > +}
> > > > > > > > diff --git a/src/v4l2/v4l2_camera.h b/src/v4l2/v4l2_camera.h
> > > > > > > > index a095f4e27524..4b5618ac12b5 100644
> > > > > > > > --- a/src/v4l2/v4l2_camera.h
> > > > > > > > +++ b/src/v4l2/v4l2_camera.h
> > > > > > > > @@ -45,8 +45,7 @@ public:
> > > > > > > >         std::vector<Buffer> completedBuffers();
> > > > > > > >
> > > > > > > >         int configure(StreamConfiguration *streamConfigOut,
> > > > > > > > -                     const Size &size, const PixelFormat &pixelformat,
> > > > > > > > -                     unsigned int bufferCount);
> > > > > > > > +                     const Size &size, const PixelFormat &pixelformat);
> > > > > > > >         int validateConfiguration(const PixelFormat &pixelformat,
> > > > > > > >                                   const Size &size,
> > > > > > > >                                   StreamConfiguration *streamConfigOut);
> > > > > > > > @@ -65,6 +64,8 @@ public:
> > > > > > > >
> > > > > > > >         bool isRunning();
> > > > > > > >
> > > > > > > > +       unsigned int minimumRequests(unsigned int count);
> > > > > > > > +
> > > > > > > >  private:
> > > > > > > >         void requestComplete(Request *request);
> > > > > > > >
> > > > > > > > diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
> > > > > > > > index 7682c4bddf90..634ec84e0cbb 100644
> > > > > > > > --- a/src/v4l2/v4l2_camera_proxy.cpp
> > > > > > > > +++ b/src/v4l2/v4l2_camera_proxy.cpp
> > > > > > > > @@ -349,8 +349,7 @@ int V4L2CameraProxy::vidioc_s_fmt(V4L2CameraFile *file, struct v4l2_format *arg)
> > > > > > > >         Size size(arg->fmt.pix.width, arg->fmt.pix.height);
> > > > > > > >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(arg->fmt.pix.pixelformat);
> > > > > > > >         ret = vcam_->configure(&streamConfig_, size,
> > > > > > > > -                              PixelFormatInfo::info(v4l2Format).format,
> > > > > > > > -                              bufferCount_);
> > > > > > > > +                              PixelFormatInfo::info(v4l2Format).format);
> > > > > > > >         if (ret < 0)
> > > > > > > >                 return -EINVAL;
> > > > > > > >
> > > > > > > > @@ -491,14 +490,13 @@ int V4L2CameraProxy::vidioc_reqbufs(V4L2CameraFile *file, struct v4l2_requestbuf
> > > > > > > >         Size size(v4l2PixFormat_.width, v4l2PixFormat_.height);
> > > > > > > >         V4L2PixelFormat v4l2Format = V4L2PixelFormat(v4l2PixFormat_.pixelformat);
> > > > > > > >         int ret = vcam_->configure(&streamConfig_, size,
> > > > > > > > -                                  PixelFormatInfo::info(v4l2Format).format,
> > > > > > > > -                                  arg->count);
> > > > > > > > +                                  PixelFormatInfo::info(v4l2Format).format);
> > > > > > > >         if (ret < 0)
> > > > > > > >                 return -EINVAL;
> > > > > > > >
> > > > > > > >         setFmtFromConfig(streamConfig_);
> > > > > > > >
> > > > > > > > -       arg->count = streamConfig_.bufferCount;
> > > > > > > > +       arg->count = vcam_->minimumRequests(arg->count);
> > > > > > > >         bufferCount_ = arg->count;
> > > > > > > >
> > > > > > > >         ret = vcam_->allocBuffers(arg->count);
> > > > > > > > diff --git a/test/camera/buffer_import.cpp b/test/camera/buffer_import.cpp
> > > > > > > > index c504ea09e64b..67ac0ad20e15 100644
> > > > > > > > --- a/test/camera/buffer_import.cpp
> > > > > > > > +++ b/test/camera/buffer_import.cpp
> > > > > > > > @@ -16,6 +16,8 @@
> > > > > > > >  #include <libcamera/base/thread.h>
> > > > > > > >  #include <libcamera/base/timer.h>
> > > > > > > >
> > > > > > > > +#include <libcamera/property_ids.h>
> > > > > > > > +
> > > > > > > >  #include "libcamera/internal/device_enumerator.h"
> > > > > > > >  #include "libcamera/internal/media_device.h"
> > > > > > > >  #include "libcamera/internal/v4l2_videodevice.h"
> > > > > > > > @@ -92,10 +94,12 @@ protected:
> > > > > > > >                         return TestFail;
> > > > > > > >                 }
> > > > > > > >
> > > > > > > > +               unsigned int bufferCount = camera_->properties().get(properties::MinimumRequests);
> > > > > > > > +
> > > > > > > >                 Stream *stream = cfg.stream();
> > > > > > > >
> > > > > > > >                 BufferSource source;
> > > > > > > > -               int ret = source.allocate(cfg);
> > > > > > > > +               int ret = source.allocate(cfg, bufferCount);
> > > > > > > >                 if (ret != TestPass)
> > > > > > > >                         return ret;
> > > > > > > >
> > > > > > > > @@ -139,10 +143,10 @@ protected:
> > > > > > > >                 while (timer.isRunning())
> > > > > > > >                         dispatcher->processEvents();
> > > > > > > >
> > > > > > > > -               if (completeRequestsCount_ < cfg.bufferCount * 2) {
> > > > > > > > +               if (completeRequestsCount_ < bufferCount * 2) {
> > > > > > > >                         std::cout << "Failed to capture enough frames (got "
> > > > > > > >                                   << completeRequestsCount_ << " expected at least "
> > > > > > > > -                                 << cfg.bufferCount * 2 << ")" << std::endl;
> > > > > > > > +                                 << bufferCount * 2 << ")" << std::endl;
> > > > > > > >                         return TestFail;
> > > > > > > >                 }
> > > > > > > >
> > > > > > > > diff --git a/test/libtest/buffer_source.cpp b/test/libtest/buffer_source.cpp
> > > > > > > > index 73563f2fc39d..c3d5286a2462 100644
> > > > > > > > --- a/test/libtest/buffer_source.cpp
> > > > > > > > +++ b/test/libtest/buffer_source.cpp
> > > > > > > > @@ -24,7 +24,7 @@ BufferSource::~BufferSource()
> > > > > > > >                 media_->release();
> > > > > > > >  }
> > > > > > > >
> > > > > > > > -int BufferSource::allocate(const StreamConfiguration &config)
> > > > > > > > +int BufferSource::allocate(const StreamConfiguration &config, unsigned int count)
> > > > > > > >  {
> > > > > > > >         /* Locate and open the video device. */
> > > > > > > >         std::string videoDeviceName = "vivid-000-vid-out";
> > > > > > > > @@ -77,7 +77,7 @@ int BufferSource::allocate(const StreamConfiguration &config)
> > > > > > > >                 return TestFail;
> > > > > > > >         }
> > > > > > > >
> > > > > > > > -       if (video->allocateBuffers(config.bufferCount, &buffers_) < 0) {
> > > > > > > > +       if (video->allocateBuffers(count, &buffers_) < 0) {
> > > > > > > >                 std::cout << "Failed to allocate buffers" << std::endl;
> > > > > > > >                 return TestFail;
> > > > > > > >         }
> > > > > > > > diff --git a/test/libtest/buffer_source.h b/test/libtest/buffer_source.h
> > > > > > > > index 14b4770e8d8a..6a18e269a575 100644
> > > > > > > > --- a/test/libtest/buffer_source.h
> > > > > > > > +++ b/test/libtest/buffer_source.h
> > > > > > > > @@ -20,7 +20,7 @@ public:
> > > > > > > >         BufferSource();
> > > > > > > >         ~BufferSource();
> > > > > > > >
> > > > > > > > -       int allocate(const StreamConfiguration &config);
> > > > > > > > +       int allocate(const StreamConfiguration &config, unsigned int count);
> > > > > > > >         const std::vector<std::unique_ptr<FrameBuffer>> &buffers();
> > > > > > > >
> > > > > > > >  private:
> > > > > > > > diff --git a/test/v4l2_videodevice/buffer_cache.cpp b/test/v4l2_videodevice/buffer_cache.cpp
> > > > > > > > index b3f2bec11783..07fddfd2617c 100644
> > > > > > > > --- a/test/v4l2_videodevice/buffer_cache.cpp
> > > > > > > > +++ b/test/v4l2_videodevice/buffer_cache.cpp
> > > > > > > > @@ -10,6 +10,7 @@
> > > > > > > >  #include <vector>
> > > > > > > >
> > > > > > > >  #include <libcamera/formats.h>
> > > > > > > > +#include <libcamera/property_ids.h>
> > > > > > > >  #include <libcamera/stream.h>
> > > > > > > >
> > > > > > > >  #include "buffer_source.h"
> > > > > > > > @@ -145,10 +146,9 @@ public:
> > > > > > > >                 StreamConfiguration cfg;
> > > > > > > >                 cfg.pixelFormat = formats::YUYV;
> > > > > > > >                 cfg.size = Size(600, 800);
> > > > > > > > -               cfg.bufferCount = numBuffers;
> > > > > > > >
> > > > > > > >                 BufferSource source;
> > > > > > > > -               int ret = source.allocate(cfg);
> > > > > > > > +               int ret = source.allocate(cfg, numBuffers);
> > > > > > > >                 if (ret != TestPass)
> > > > > > > >                         return ret;
> > > > > > > >

Hi Nícolas,

Thank you for the patch.

On Thu, Jul 22, 2021 at 08:28:50PM -0300, Nícolas F. R. A. Prado wrote:
> Now that the number of buffers allocated by the FrameBufferAllocator
> helper is passed through FrameBufferAllocator::allocate() and the
> pipelines no longer use bufferCount for internal buffer or V4L2 buffer
> slots allocation, we no longer need to have bufferCount in the
> StreamConfiguration, so remove it.
> 
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
> ---
> 
> No changes in v7
> 
> Changes in v6:
> - Removed IPU3_BUFFER_COUNT as it was unused
> 
>  include/libcamera/stream.h                         |  2 --
>  src/android/camera_stream.cpp                      |  2 +-
>  src/libcamera/pipeline/ipu3/cio2.cpp               |  1 -
>  src/libcamera/pipeline/ipu3/ipu3.cpp               |  8 --------
>  src/libcamera/pipeline/raspberrypi/raspberrypi.cpp |  6 ------
>  src/libcamera/pipeline/rkisp1/rkisp1_path.cpp      |  2 --
>  src/libcamera/pipeline/simple/converter.cpp        |  3 ---
>  src/libcamera/pipeline/simple/converter.h          |  3 ---
>  src/libcamera/pipeline/simple/simple.cpp           |  5 +----
>  src/libcamera/pipeline/uvcvideo/uvcvideo.cpp       |  3 ---
>  src/libcamera/pipeline/vimc/vimc.cpp               |  3 ---
>  src/libcamera/stream.cpp                           |  9 ++-------
>  src/v4l2/v4l2_camera.cpp                           | 14 ++++++++++----
>  src/v4l2/v4l2_camera.h                             |  5 +++--
>  src/v4l2/v4l2_camera_proxy.cpp                     |  8 +++-----
>  test/camera/buffer_import.cpp                      | 10 +++++++---
>  test/libtest/buffer_source.cpp                     |  4 ++--
>  test/libtest/buffer_source.h                       |  2 +-
>  test/v4l2_videodevice/buffer_cache.cpp             |  4 ++--
>  19 files changed, 32 insertions(+), 62 deletions(-)
> 
> diff --git a/include/libcamera/stream.h b/include/libcamera/stream.h
> index 0c55e7164592..b25f0059f2f1 100644
> --- a/include/libcamera/stream.h
> +++ b/include/libcamera/stream.h
> @@ -45,8 +45,6 @@ struct StreamConfiguration {
>  	unsigned int stride;
>  	unsigned int frameSize;
>  
> -	unsigned int bufferCount;
> -
>  	Stream *stream() const { return stream_; }
>  	void setStream(Stream *stream) { stream_ = stream; }
>  	const StreamFormats &formats() const { return formats_; }
> diff --git a/src/android/camera_stream.cpp b/src/android/camera_stream.cpp
> index b168e3c0c288..0794be409f82 100644
> --- a/src/android/camera_stream.cpp
> +++ b/src/android/camera_stream.cpp
> @@ -94,7 +94,7 @@ int CameraStream::configure()
>  			buffers_.push_back(frameBuffer.get());
>  	}
>  
> -	camera3Stream_->max_buffers = configuration().bufferCount;
> +	camera3Stream_->max_buffers = bufferCount;
>  
>  	return 0;
>  }
> diff --git a/src/libcamera/pipeline/ipu3/cio2.cpp b/src/libcamera/pipeline/ipu3/cio2.cpp
> index 1bcd580e251c..0e04e7214489 100644
> --- a/src/libcamera/pipeline/ipu3/cio2.cpp
> +++ b/src/libcamera/pipeline/ipu3/cio2.cpp
> @@ -214,7 +214,6 @@ StreamConfiguration CIO2Device::generateConfiguration(Size size) const
>  
>  	cfg.size = sensorFormat.size;
>  	cfg.pixelFormat = mbusCodesToPixelFormat.at(sensorFormat.mbus_code);
> -	cfg.bufferCount = CIO2_BUFFER_COUNT;
>  
>  	return cfg;
>  }
> diff --git a/src/libcamera/pipeline/ipu3/ipu3.cpp b/src/libcamera/pipeline/ipu3/ipu3.cpp
> index 4efd201c05e5..b223b3f33cd0 100644
> --- a/src/libcamera/pipeline/ipu3/ipu3.cpp
> +++ b/src/libcamera/pipeline/ipu3/ipu3.cpp
> @@ -38,7 +38,6 @@ namespace libcamera {
>  
>  LOG_DEFINE_CATEGORY(IPU3)
>  
> -static constexpr unsigned int IPU3_BUFFER_COUNT = 4;
>  static constexpr unsigned int IPU3_MAX_STREAMS = 3;
>  static const Size IMGU_OUTPUT_MIN_SIZE = { 2, 2 };
>  static const Size IMGU_OUTPUT_MAX_SIZE = { 4480, 34004 };
> @@ -295,7 +294,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
>  			/* Initialize the RAW stream with the CIO2 configuration. */
>  			cfg->size = cio2Configuration_.size;
>  			cfg->pixelFormat = cio2Configuration_.pixelFormat;
> -			cfg->bufferCount = cio2Configuration_.bufferCount;
>  			cfg->stride = info.stride(cfg->size.width, 0, 64);
>  			cfg->frameSize = info.frameSize(cfg->size, 64);
>  			cfg->setStream(const_cast<Stream *>(&data_->rawStream_));
> @@ -339,7 +337,6 @@ CameraConfiguration::Status IPU3CameraConfiguration::validate()
>  					      IMGU_OUTPUT_HEIGHT_ALIGN);
>  
>  			cfg->pixelFormat = formats::NV12;
> -			cfg->bufferCount = IPU3_BUFFER_COUNT;
>  			cfg->stride = info.stride(cfg->size.width, 0, 1);
>  			cfg->frameSize = info.frameSize(cfg->size, 1);
>  
> @@ -407,7 +404,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
>  	Size sensorResolution = data->cio2_.sensor()->resolution();
>  	for (const StreamRole role : roles) {
>  		std::map<PixelFormat, std::vector<SizeRange>> streamFormats;
> -		unsigned int bufferCount;
>  		PixelFormat pixelFormat;
>  		Size size;
>  
> @@ -428,7 +424,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
>  			size.height = utils::alignDown(size.height - 1,
>  						       IMGU_OUTPUT_HEIGHT_MARGIN);
>  			pixelFormat = formats::NV12;
> -			bufferCount = IPU3_BUFFER_COUNT;
>  			streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
>  
>  			break;
> @@ -438,7 +433,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
>  				data->cio2_.generateConfiguration(sensorResolution);
>  			pixelFormat = cio2Config.pixelFormat;
>  			size = cio2Config.size;
> -			bufferCount = cio2Config.bufferCount;
>  
>  			for (const PixelFormat &format : data->cio2_.formats())
>  				streamFormats[format] = data->cio2_.sizes();
> @@ -457,7 +451,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
>  					       .alignedDownTo(IMGU_OUTPUT_WIDTH_ALIGN,
>  							      IMGU_OUTPUT_HEIGHT_ALIGN);
>  			pixelFormat = formats::NV12;
> -			bufferCount = IPU3_BUFFER_COUNT;
>  			streamFormats[pixelFormat] = { { IMGU_OUTPUT_MIN_SIZE, size } };
>  
>  			break;
> @@ -474,7 +467,6 @@ CameraConfiguration *PipelineHandlerIPU3::generateConfiguration(Camera *camera,
>  		StreamConfiguration cfg(formats);
>  		cfg.size = size;
>  		cfg.pixelFormat = pixelFormat;
> -		cfg.bufferCount = bufferCount;
>  		config->addConfiguration(cfg);
>  	}
>  
> diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> index 776e0f92aed1..e6fc0425c3ef 100644
> --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> @@ -473,7 +473,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
>  	RPiCameraData *data = cameraData(camera);
>  	CameraConfiguration *config = new RPiCameraConfiguration(data);
>  	V4L2DeviceFormat sensorFormat;
> -	unsigned int bufferCount;
>  	PixelFormat pixelFormat;
>  	V4L2VideoDevice::Formats fmts;
>  	Size size;
> @@ -491,7 +490,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
>  			sensorFormat = findBestMode(fmts, size);
>  			pixelFormat = sensorFormat.fourcc.toPixelFormat();
>  			ASSERT(pixelFormat.isValid());
> -			bufferCount = 2;
>  			rawCount++;
>  			break;
>  
> @@ -500,7 +498,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
>  			pixelFormat = formats::NV12;
>  			/* Return the largest sensor resolution. */
>  			size = data->sensor_->resolution();
> -			bufferCount = 1;
>  			outCount++;
>  			break;
>  
> @@ -516,7 +513,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
>  			fmts = data->isp_[Isp::Output0].dev()->formats();
>  			pixelFormat = formats::YUV420;
>  			size = { 1920, 1080 };
> -			bufferCount = 4;
>  			outCount++;
>  			break;
>  
> @@ -524,7 +520,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
>  			fmts = data->isp_[Isp::Output0].dev()->formats();
>  			pixelFormat = formats::ARGB8888;
>  			size = { 800, 600 };
> -			bufferCount = 4;
>  			outCount++;
>  			break;
>  
> @@ -554,7 +549,6 @@ CameraConfiguration *PipelineHandlerRPi::generateConfiguration(Camera *camera,
>  		StreamConfiguration cfg(formats);
>  		cfg.size = size;
>  		cfg.pixelFormat = pixelFormat;
> -		cfg.bufferCount = bufferCount;
>  		config->addConfiguration(cfg);
>  	}
>  
> diff --git a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> index fea330f72886..4961f3971e59 100644
> --- a/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> +++ b/src/libcamera/pipeline/rkisp1/rkisp1_path.cpp
> @@ -61,7 +61,6 @@ StreamConfiguration RkISP1Path::generateConfiguration(const Size &resolution)
>  	StreamConfiguration cfg(formats);
>  	cfg.pixelFormat = formats::NV12;
>  	cfg.size = maxResolution;
> -	cfg.bufferCount = RKISP1_BUFFER_COUNT;
>  
>  	return cfg;
>  }
> @@ -77,7 +76,6 @@ CameraConfiguration::Status RkISP1Path::validate(StreamConfiguration *cfg)
>  
>  	cfg->size.boundTo(maxResolution_);
>  	cfg->size.expandTo(minResolution_);
> -	cfg->bufferCount = RKISP1_BUFFER_COUNT;
>  
>  	V4L2DeviceFormat format;
>  	format.fourcc = video_->toV4L2PixelFormat(cfg->pixelFormat);
> diff --git a/src/libcamera/pipeline/simple/converter.cpp b/src/libcamera/pipeline/simple/converter.cpp
> index b3bcf01483f7..fda417793e80 100644
> --- a/src/libcamera/pipeline/simple/converter.cpp
> +++ b/src/libcamera/pipeline/simple/converter.cpp
> @@ -89,9 +89,6 @@ int SimpleConverter::Stream::configure(const StreamConfiguration &inputCfg,
>  		return -EINVAL;
>  	}
>  
> -	inputBufferCount_ = inputCfg.bufferCount;
> -	outputBufferCount_ = outputCfg.bufferCount;
> -
>  	return 0;
>  }
>  
> diff --git a/src/libcamera/pipeline/simple/converter.h b/src/libcamera/pipeline/simple/converter.h
> index 7e1d60674f62..406e63ca2a80 100644
> --- a/src/libcamera/pipeline/simple/converter.h
> +++ b/src/libcamera/pipeline/simple/converter.h
> @@ -87,9 +87,6 @@ private:
>  		SimpleConverter *converter_;
>  		unsigned int index_;
>  		std::unique_ptr<V4L2M2MDevice> m2m_;
> -
> -		unsigned int inputBufferCount_;
> -		unsigned int outputBufferCount_;
>  	};
>  
>  	std::string deviceNode_;
> diff --git a/src/libcamera/pipeline/simple/simple.cpp b/src/libcamera/pipeline/simple/simple.cpp
> index a1163eaf8be2..ded04914f610 100644
> --- a/src/libcamera/pipeline/simple/simple.cpp
> +++ b/src/libcamera/pipeline/simple/simple.cpp
> @@ -628,7 +628,7 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
>  		    cfg.size != pipeConfig_->captureSize)
>  			needConversion_ = true;
>  
> -		/* Set the stride, frameSize and bufferCount. */
> +		/* Set the stride and frameSize. */
>  		if (needConversion_) {
>  			std::tie(cfg.stride, cfg.frameSize) =
>  				converter->strideAndFrameSize(cfg.pixelFormat, cfg.size);
> @@ -646,8 +646,6 @@ CameraConfiguration::Status SimpleCameraConfiguration::validate()
>  			cfg.stride = format.planes[0].bpl;
>  			cfg.frameSize = format.planes[0].size;
>  		}
> -
> -		cfg.bufferCount = 3;
>  	}
>  
>  	return status;
> @@ -770,7 +768,6 @@ int SimplePipelineHandler::configure(Camera *camera, CameraConfiguration *c)
>  	inputCfg.pixelFormat = pipeConfig->captureFormat;
>  	inputCfg.size = pipeConfig->captureSize;
>  	inputCfg.stride = captureFormat.planes[0].bpl;
> -	inputCfg.bufferCount = kNumInternalBuffers;

You should also drop the kNumInternalBuffers constant.

>  
>  	return converter_->configure(inputCfg, outputCfgs);
>  }
> diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> index 755949e7a59a..32482300f09a 100644
> --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> @@ -150,8 +150,6 @@ CameraConfiguration::Status UVCCameraConfiguration::validate()
>  		status = Adjusted;
>  	}
>  
> -	cfg.bufferCount = 4;
> -
>  	V4L2DeviceFormat format;
>  	format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
>  	format.size = cfg.size;
> @@ -193,7 +191,6 @@ CameraConfiguration *PipelineHandlerUVC::generateConfiguration(Camera *camera,
>  
>  	cfg.pixelFormat = formats.pixelformats().front();
>  	cfg.size = formats.sizes(cfg.pixelFormat).back();
> -	cfg.bufferCount = 4;
>  
>  	config->addConfiguration(cfg);
>  
> diff --git a/src/libcamera/pipeline/vimc/vimc.cpp b/src/libcamera/pipeline/vimc/vimc.cpp
> index 24ba743a946c..a698427c4361 100644
> --- a/src/libcamera/pipeline/vimc/vimc.cpp
> +++ b/src/libcamera/pipeline/vimc/vimc.cpp
> @@ -167,8 +167,6 @@ CameraConfiguration::Status VimcCameraConfiguration::validate()
>  		status = Adjusted;
>  	}
>  
> -	cfg.bufferCount = 4;
> -
>  	V4L2DeviceFormat format;
>  	format.fourcc = data_->video_->toV4L2PixelFormat(cfg.pixelFormat);
>  	format.size = cfg.size;
> @@ -224,7 +222,6 @@ CameraConfiguration *PipelineHandlerVimc::generateConfiguration(Camera *camera,
>  
>  	cfg.pixelFormat = formats::BGR888;
>  	cfg.size = { 1920, 1080 };
> -	cfg.bufferCount = 4;
>  
>  	config->addConfiguration(cfg);
>  
> diff --git a/src/libcamera/stream.cpp b/src/libcamera/stream.cpp
> index b8626775d224..ca507b72b26a 100644
> --- a/src/libcamera/stream.cpp
> +++ b/src/libcamera/stream.cpp
> @@ -280,7 +280,7 @@ SizeRange StreamFormats::range(const PixelFormat &pixelformat) const
>   * handlers provide StreamFormats.
>   */
>  StreamConfiguration::StreamConfiguration()
> -	: pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> +	: pixelFormat(0), stride(0), frameSize(0),
>  	  stream_(nullptr)

This now holds on a single line.

>  {
>  }
> @@ -289,7 +289,7 @@ StreamConfiguration::StreamConfiguration()
>   * \brief Construct a configuration with stream formats
>   */
>  StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
> -	: pixelFormat(0), stride(0), frameSize(0), bufferCount(0),
> +	: pixelFormat(0), stride(0), frameSize(0),
>  	  stream_(nullptr), formats_(formats)
>  {
>  }
> @@ -324,11 +324,6 @@ StreamConfiguration::StreamConfiguration(const StreamFormats &formats)
>   * validating the configuration with a call to CameraConfiguration::validate().
>   */
>  
> -/**
> - * \var StreamConfiguration::bufferCount
> - * \brief Requested number of buffers to allocate for the stream
> - */
> -
>  /**
>   * \fn StreamConfiguration::stream()
>   * \brief Retrieve the stream associated with the configuration
> diff --git a/src/v4l2/v4l2_camera.cpp b/src/v4l2/v4l2_camera.cpp
> index d01eacfa2b84..2ff9affc6388 100644
> --- a/src/v4l2/v4l2_camera.cpp
> +++ b/src/v4l2/v4l2_camera.cpp
> @@ -12,6 +12,8 @@
>  
>  #include <libcamera/base/log.h>
>  
> +#include <libcamera/property_ids.h>
> +
>  using namespace libcamera;
>  
>  LOG_DECLARE_CATEGORY(V4L2Compat)
> @@ -107,14 +109,12 @@ void V4L2Camera::requestComplete(Request *request)
>  }
>  
>  int V4L2Camera::configure(StreamConfiguration *streamConfigOut,
> -			  const Size &size, const PixelFormat &pixelformat,
> -			  unsigned int bufferCount)
> +			  const Size &size, const PixelFormat &pixelformat)
>  {
>  	StreamConfiguration &streamConfig = config_->at(0);
>  	streamConfig.size.width = size.width;
>  	streamConfig.size.height = size.height;
>  	streamConfig.pixelFormat = pixelformat;
> -	streamConfig.bufferCount = bufferCount;
>  	/* \todo memoryType (interval vs external) */

While at it, could you s/interval/internal/ ?

>  
>  	CameraConfiguration::Status validation = config_->validate();
> @@ -146,7 +146,6 @@ int V4L2Camera::validateConfiguration(const PixelFormat &pixelFormat,
>  	StreamConfiguration &cfg = config->at(0);
>  	cfg.size = size;
>  	cfg.pixelFormat = pixelFormat;
> -	cfg.bufferCount = 1;
>  
>  	CameraConfiguration::Status validation = config->validate();
>  	if (validation == CameraConfiguration::Invalid)
> @@ -299,3 +298,10 @@ bool V4L2Camera::isRunning()
>  {
>  	return isRunning_;
>  }
> +
> +unsigned int V4L2Camera::minimumRequests(unsigned int count)
> +{
> +	unsigned int min = camera_->properties().get(properties::MinimumRequests);
> +
> +	return std::max(count, min);
> +}

The rework of the V4L2 adaptation layer should go to a separate patch,
it's not just about removing bufferCount.

How about making this a function that just returns the value of the
property, and moving the std::max() to the caller ?

> diff --git a/src/v4l2/v4l2_camera.h b/src/v4l2/v4l2_camera.h
> index a095f4e27524..4b5618ac12b5 100644
> --- a/src/v4l2/v4l2_camera.h
> +++ b/src/v4l2/v4l2_camera.h
> @@ -45,8 +45,7 @@ public:
>  	std::vector<Buffer> completedBuffers();
>  
>  	int configure(StreamConfiguration *streamConfigOut,
> -		      const Size &size, const PixelFormat &pixelformat,
> -		      unsigned int bufferCount);
> +		      const Size &size, const PixelFormat &pixelformat);
>  	int validateConfiguration(const PixelFormat &pixelformat,
>  				  const Size &size,
>  				  StreamConfiguration *streamConfigOut);
> @@ -65,6 +64,8 @@ public:
>  
>  	bool isRunning();
>  
> +	unsigned int minimumRequests(unsigned int count);
> +
>  private:
>  	void requestComplete(Request *request);
>  
> diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
> index 7682c4bddf90..634ec84e0cbb 100644
> --- a/src/v4l2/v4l2_camera_proxy.cpp
> +++ b/src/v4l2/v4l2_camera_proxy.cpp
> @@ -349,8 +349,7 @@ int V4L2CameraProxy::vidioc_s_fmt(V4L2CameraFile *file, struct v4l2_format *arg)
>  	Size size(arg->fmt.pix.width, arg->fmt.pix.height);
>  	V4L2PixelFormat v4l2Format = V4L2PixelFormat(arg->fmt.pix.pixelformat);
>  	ret = vcam_->configure(&streamConfig_, size,
> -			       PixelFormatInfo::info(v4l2Format).format,
> -			       bufferCount_);
> +			       PixelFormatInfo::info(v4l2Format).format);
>  	if (ret < 0)
>  		return -EINVAL;
>  
> @@ -491,14 +490,13 @@ int V4L2CameraProxy::vidioc_reqbufs(V4L2CameraFile *file, struct v4l2_requestbuf
>  	Size size(v4l2PixFormat_.width, v4l2PixFormat_.height);
>  	V4L2PixelFormat v4l2Format = V4L2PixelFormat(v4l2PixFormat_.pixelformat);
>  	int ret = vcam_->configure(&streamConfig_, size,
> -				   PixelFormatInfo::info(v4l2Format).format,
> -				   arg->count);
> +				   PixelFormatInfo::info(v4l2Format).format);
>  	if (ret < 0)
>  		return -EINVAL;
>  
>  	setFmtFromConfig(streamConfig_);
>  
> -	arg->count = streamConfig_.bufferCount;
> +	arg->count = vcam_->minimumRequests(arg->count);
>  	bufferCount_ = arg->count;
>  
>  	ret = vcam_->allocBuffers(arg->count);

Unless I'm mistaken, allocBuffers() could return a lower buffer count
than requested, this should be taken into account.

> diff --git a/test/camera/buffer_import.cpp b/test/camera/buffer_import.cpp
> index c504ea09e64b..67ac0ad20e15 100644
> --- a/test/camera/buffer_import.cpp
> +++ b/test/camera/buffer_import.cpp
> @@ -16,6 +16,8 @@
>  #include <libcamera/base/thread.h>
>  #include <libcamera/base/timer.h>
>  
> +#include <libcamera/property_ids.h>
> +
>  #include "libcamera/internal/device_enumerator.h"
>  #include "libcamera/internal/media_device.h"
>  #include "libcamera/internal/v4l2_videodevice.h"
> @@ -92,10 +94,12 @@ protected:
>  			return TestFail;
>  		}
>  
> +		unsigned int bufferCount = camera_->properties().get(properties::MinimumRequests);
> +
>  		Stream *stream = cfg.stream();
>  
>  		BufferSource source;
> -		int ret = source.allocate(cfg);
> +		int ret = source.allocate(cfg, bufferCount);
>  		if (ret != TestPass)
>  			return ret;
>  
> @@ -139,10 +143,10 @@ protected:
>  		while (timer.isRunning())
>  			dispatcher->processEvents();
>  
> -		if (completeRequestsCount_ < cfg.bufferCount * 2) {
> +		if (completeRequestsCount_ < bufferCount * 2) {
>  			std::cout << "Failed to capture enough frames (got "
>  				  << completeRequestsCount_ << " expected at least "
> -				  << cfg.bufferCount * 2 << ")" << std::endl;
> +				  << bufferCount * 2 << ")" << std::endl;
>  			return TestFail;
>  		}
>  
> diff --git a/test/libtest/buffer_source.cpp b/test/libtest/buffer_source.cpp
> index 73563f2fc39d..c3d5286a2462 100644
> --- a/test/libtest/buffer_source.cpp
> +++ b/test/libtest/buffer_source.cpp
> @@ -24,7 +24,7 @@ BufferSource::~BufferSource()
>  		media_->release();
>  }
>  
> -int BufferSource::allocate(const StreamConfiguration &config)
> +int BufferSource::allocate(const StreamConfiguration &config, unsigned int count)
>  {
>  	/* Locate and open the video device. */
>  	std::string videoDeviceName = "vivid-000-vid-out";
> @@ -77,7 +77,7 @@ int BufferSource::allocate(const StreamConfiguration &config)
>  		return TestFail;
>  	}
>  
> -	if (video->allocateBuffers(config.bufferCount, &buffers_) < 0) {
> +	if (video->allocateBuffers(count, &buffers_) < 0) {
>  		std::cout << "Failed to allocate buffers" << std::endl;
>  		return TestFail;
>  	}
> diff --git a/test/libtest/buffer_source.h b/test/libtest/buffer_source.h
> index 14b4770e8d8a..6a18e269a575 100644
> --- a/test/libtest/buffer_source.h
> +++ b/test/libtest/buffer_source.h
> @@ -20,7 +20,7 @@ public:
>  	BufferSource();
>  	~BufferSource();
>  
> -	int allocate(const StreamConfiguration &config);
> +	int allocate(const StreamConfiguration &config, unsigned int count);
>  	const std::vector<std::unique_ptr<FrameBuffer>> &buffers();
>  
>  private:
> diff --git a/test/v4l2_videodevice/buffer_cache.cpp b/test/v4l2_videodevice/buffer_cache.cpp
> index b3f2bec11783..07fddfd2617c 100644
> --- a/test/v4l2_videodevice/buffer_cache.cpp
> +++ b/test/v4l2_videodevice/buffer_cache.cpp
> @@ -10,6 +10,7 @@
>  #include <vector>
>  
>  #include <libcamera/formats.h>
> +#include <libcamera/property_ids.h>
>  #include <libcamera/stream.h>
>  
>  #include "buffer_source.h"
> @@ -145,10 +146,9 @@ public:
>  		StreamConfiguration cfg;
>  		cfg.pixelFormat = formats::YUYV;
>  		cfg.size = Size(600, 800);
> -		cfg.bufferCount = numBuffers;
>  
>  		BufferSource source;
> -		int ret = source.allocate(cfg);
> +		int ret = source.allocate(cfg, numBuffers);
>  		if (ret != TestPass)
>  			return ret;
>