[libcamera-devel,v5,6/7] libcamera: v4l2_videodevice: Match formats supported by the device

16932 diff mbox series

Now that V4L2PixelFormat::fromPixelFormat() returns a list of formats
to chose from, select the one supported by the video device by matching
against the list of supported pixel formats.

The first format found to match one of the device supported ones is
returned.

As the list of pixel formats supported by the video device does not
change at run-time, cache it at device open() time. To maximize the
lookup efficiency store the list of supported V4L2PixelFormat in an
std::unordered_set<> which requires a specialization of
std::hash<V4L2PixelFormat> to be injected in the std namespace.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 include/libcamera/internal/v4l2_pixelformat.h | 13 +++++
 include/libcamera/internal/v4l2_videodevice.h |  4 ++
 src/libcamera/v4l2_videodevice.cpp            | 57 +++++++++++++++----
 3 files changed, 62 insertions(+), 12 deletions(-)

Hi Jacopo,

On Wed, Aug 03, 2022 at 12:38:48PM +0200, Jacopo Mondi wrote:
> Now that V4L2PixelFormat::fromPixelFormat() returns a list of formats
> to chose from, select the one supported by the video device by matching
> against the list of supported pixel formats.
> 
> The first format found to match one of the device supported ones is
> returned.
> 
> As the list of pixel formats supported by the video device does not
> change at run-time, cache it at device open() time. To maximize the
> lookup efficiency store the list of supported V4L2PixelFormat in an
> std::unordered_set<> which requires a specialization of
> std::hash<V4L2PixelFormat> to be injected in the std namespace.

Would you mind including the patch I sent to add
std::hash<V4L2PixelFormat> in this series and rebasing this on top ?
It's a separate function change, and if we later want to hash
PixelFormat too, it will show how to do so (with a commit message
template) without unrelated changes.

The commit message here should then drop " ... which requires " unwards,
and you can also drop my SoB line.

> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---
>  include/libcamera/internal/v4l2_pixelformat.h | 13 +++++
>  include/libcamera/internal/v4l2_videodevice.h |  4 ++
>  src/libcamera/v4l2_videodevice.cpp            | 57 +++++++++++++++----
>  3 files changed, 62 insertions(+), 12 deletions(-)
> 
> diff --git a/include/libcamera/internal/v4l2_pixelformat.h b/include/libcamera/internal/v4l2_pixelformat.h
> index d5400f90a67e..34d283db44f4 100644
> --- a/include/libcamera/internal/v4l2_pixelformat.h
> +++ b/include/libcamera/internal/v4l2_pixelformat.h
> @@ -8,6 +8,7 @@
>  
>  #pragma once
>  
> +#include <functional>
>  #include <ostream>
>  #include <stdint.h>
>  #include <string>
> @@ -55,3 +56,15 @@ private:
>  std::ostream &operator<<(std::ostream &out, const V4L2PixelFormat &f);
>  
>  } /* namespace libcamera */
> +
> +namespace std {
> +
> +template<>
> +struct hash<libcamera::V4L2PixelFormat> {
> +	size_t operator()(libcamera::V4L2PixelFormat const &format) const noexcept
> +	{
> +		return format.fourcc();
> +	}
> +};
> +
> +} /* namespace std */
> diff --git a/include/libcamera/internal/v4l2_videodevice.h b/include/libcamera/internal/v4l2_videodevice.h
> index 29fa0bbaf670..ed98a284de16 100644
> --- a/include/libcamera/internal/v4l2_videodevice.h
> +++ b/include/libcamera/internal/v4l2_videodevice.h
> @@ -14,6 +14,7 @@
>  #include <ostream>
>  #include <stdint.h>
>  #include <string>
> +#include <unordered_set>
>  #include <vector>
>  
>  #include <linux/videodev2.h>
> @@ -242,6 +243,8 @@ private:
>  		Stopped,
>  	};
>  
> +	int initFormats();
> +
>  	int getFormatMeta(V4L2DeviceFormat *format);
>  	int trySetFormatMeta(V4L2DeviceFormat *format, bool set);
>  
> @@ -268,6 +271,7 @@ private:
>  	V4L2Capability caps_;
>  	V4L2DeviceFormat format_;
>  	const PixelFormatInfo *formatInfo_;
> +	std::unordered_set<V4L2PixelFormat> pixelFormats_;
>  
>  	enum v4l2_buf_type bufferType_;
>  	enum v4l2_memory memoryType_;
> diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
> index 2ca22f485d45..b80ee1cdbcca 100644
> --- a/src/libcamera/v4l2_videodevice.cpp
> +++ b/src/libcamera/v4l2_videodevice.cpp
> @@ -633,13 +633,9 @@ int V4L2VideoDevice::open()
>  		<< "Opened device " << caps_.bus_info() << ": "
>  		<< caps_.driver() << ": " << caps_.card();
>  
> -	ret = getFormat(&format_);
> -	if (ret) {
> -		LOG(V4L2, Error) << "Failed to get format";
> +	ret = initFormats();
> +	if (ret)
>  		return ret;
> -	}
> -
> -	formatInfo_ = &PixelFormatInfo::info(format_.fourcc);
>  
>  	return 0;
>  }
> @@ -726,7 +722,24 @@ int V4L2VideoDevice::open(SharedFD handle, enum v4l2_buf_type type)
>  		<< "Opened device " << caps_.bus_info() << ": "
>  		<< caps_.driver() << ": " << caps_.card();
>  
> -	ret = getFormat(&format_);
> +	ret = initFormats();
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +int V4L2VideoDevice::initFormats()
> +{
> +	const std::vector<V4L2PixelFormat> &deviceFormats = enumPixelformats(0);
> +	if (deviceFormats.empty()) {
> +		LOG(V4L2, Error) << "Failed to initialize device formats";
> +		return -EINVAL;
> +	}
> +
> +	pixelFormats_ = { deviceFormats.begin(), deviceFormats.end() };
> +
> +	int ret = getFormat(&format_);
>  	if (ret) {
>  		LOG(V4L2, Error) << "Failed to get format";
>  		return ret;
> @@ -1990,17 +2003,37 @@ V4L2VideoDevice::fromEntityName(const MediaDevice *media,
>  }
>  
>  /**
> - * \brief Convert \a PixelFormat to its corresponding V4L2 FourCC
> + * \brief Convert \a PixelFormat to a V4L2PixelFormat supported by the device
>   * \param[in] pixelFormat The PixelFormat to convert
>   *
> - * The V4L2 format variant the function returns the contiguous version
> - * unconditionally.
> + * Convert \a pixelformat to a V4L2 FourCC that is known to be supported by
> + * the video device.
>   *
> - * \return The V4L2_PIX_FMT_* pixel format code corresponding to \a pixelFormat
> + * A V4L2VideoDevice may support different V4L2 pixel formats that map the same
> + * PixelFormat. This is the case of the contiguous and non-contiguous variants
> + * of multiplanar formats, and with the V4L2 MJPEG and JPEG pixel formats.
> + * Converting a PixelFormat to a V4L2PixelFormat may thus have multiple answers.
> + *
> + * This function converts the \a pixelFormat using the list of V4L2 pixel
> + * formats that the V4L2VideoDevice supports. This guarantees that the returned
> + * V4L2PixelFormat will be valid for the device. If multiple matches are still
> + * possible, contiguous variants are preferred. If the \a pixelFormat is not
> + * supported by the device, the function returns an invalid V4L2PixelFormat.
> + *
> + * \return The V4L2PixelFormat corresponding to \a pixelFormat if supported by
> + * the device, or an invalid V4L2PixelFormat otherwise
>   */
>  V4L2PixelFormat V4L2VideoDevice::toV4L2PixelFormat(const PixelFormat &pixelFormat) const
>  {
> -	return V4L2PixelFormat::fromPixelFormat(pixelFormat)[0];
> +	const std::vector<V4L2PixelFormat> &v4l2PixelFormats =
> +		V4L2PixelFormat::fromPixelFormat(pixelFormat);
> +
> +	for (const V4L2PixelFormat &v4l2Format : v4l2PixelFormats) {
> +		if (pixelFormats_.count(v4l2Format))
> +			return v4l2Format;
> +	}
> +
> +	return {};
>  }
>  
>  /**