[libcamera-devel,v3,5/6] libcamera: v4l2_videodevice: Match formats supported by the device

16874 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.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
---
 include/libcamera/internal/v4l2_videodevice.h |  1 +
 src/libcamera/v4l2_videodevice.cpp            | 28 +++++++++++++++----
 2 files changed, 24 insertions(+), 5 deletions(-)

Hi Jacopo,

Thank you for the patch.

On Fri, Jul 29, 2022 at 06:00:13PM +0200, Jacopo Mondi via libcamera-devel 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.
> 
> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> ---
>  include/libcamera/internal/v4l2_videodevice.h |  1 +
>  src/libcamera/v4l2_videodevice.cpp            | 28 +++++++++++++++----
>  2 files changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/include/libcamera/internal/v4l2_videodevice.h b/include/libcamera/internal/v4l2_videodevice.h
> index 29fa0bbaf670..6fe81d5e4cf0 100644
> --- a/include/libcamera/internal/v4l2_videodevice.h
> +++ b/include/libcamera/internal/v4l2_videodevice.h
> @@ -268,6 +268,7 @@ private:
>  	V4L2Capability caps_;
>  	V4L2DeviceFormat format_;
>  	const PixelFormatInfo *formatInfo_;
> +	std::vector<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..0aeaae6ad573 100644
> --- a/src/libcamera/v4l2_videodevice.cpp
> +++ b/src/libcamera/v4l2_videodevice.cpp
> @@ -633,6 +633,8 @@ int V4L2VideoDevice::open()
>  		<< "Opened device " << caps_.bus_info() << ": "
>  		<< caps_.driver() << ": " << caps_.card();
>  
> +	pixelFormats_ = enumPixelformats(0);
> +
>  	ret = getFormat(&format_);
>  	if (ret) {
>  		LOG(V4L2, Error) << "Failed to get format";
> @@ -726,6 +728,8 @@ int V4L2VideoDevice::open(SharedFD handle, enum v4l2_buf_type type)
>  		<< "Opened device " << caps_.bus_info() << ": "
>  		<< caps_.driver() << ": " << caps_.card();
>  
> +	pixelFormats_ = enumPixelformats(0);
> +
>  	ret = getFormat(&format_);
>  	if (ret) {
>  		LOG(V4L2, Error) << "Failed to get format";
> @@ -1990,17 +1994,31 @@ V4L2VideoDevice::fromEntityName(const MediaDevice *media,
>  }
>  
>  /**
> - * \brief Convert \a PixelFormat to its corresponding V4L2 FourCC
> + * \brief Convert \a PixelFormat to one of the device supported 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

s/a\/\a/

> + * the video device.
>   *
> - * \return The V4L2_PIX_FMT_* pixel format code corresponding to \a pixelFormat
> + * \return The V4L2PixelFormat corresponding to \a pixelFormat or an invalid
> + * PixelFormat if \a pixelFormat is not supported by the video device

s/PixelFormat/V4L2PixelFormat/

I'd expand this as it's also meant to cover the JPEG vs. MJPEG case:

 * 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];
> +	std::vector<V4L2PixelFormat> v4l2PixelFormats =

	const std::vector<V4L2PixelFormat> &v4l2PixelFormats =

> +		V4L2PixelFormat::fromPixelFormat(pixelFormat);
> +
> +	for (const V4L2PixelFormat &v4l2Format : v4l2PixelFormats) {
> +		auto it = std::find_if(pixelFormats_.begin(), pixelFormats_.end(),
> +				       [&v4l2Format](const V4L2PixelFormat &devFormat) {
> +					       return v4l2Format == devFormat;
> +				       });
> +
> +		if (it != pixelFormats_.end())
> +			return v4l2Format;

Should we convert pixelFormats_ to a std::unordered_set to make the
lookup more efficient ?

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> +	}
> +
> +	return {};
>  }
>  
>  /**