[libcamera-devel] [PATCH v3] libcamera: v4l2: Set colorspace flags

[Kieran Bingham]

Quoting Umang Jain via libcamera-devel (2022-08-12 09:53:24)
> The colorspace fields are read-only from an application point of view,
> both on video devices and on subdevs, unless the
> V4L2_PIX_FMT_FLAG_SET_CSC or V4L2_MBUS_FRAMEFMT_SET_CSC flags
> (respectively) are set when calling the S_FMT ioctl.

That describes the problem, but not what the patch does. I'd append:

"""
Set the flags accordingly within the V4L2SubDevice and V4L2Device when a
colorspace is being set by the application.
"""

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

> Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
> ---
>  src/libcamera/v4l2_subdevice.cpp   |  8 +++++++-
>  src/libcamera/v4l2_videodevice.cpp | 14 ++++++++++++--
>  2 files changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp
> index e5d20f2c..d8fd92e3 100644
> --- a/src/libcamera/v4l2_subdevice.cpp
> +++ b/src/libcamera/v4l2_subdevice.cpp
> @@ -526,7 +526,13 @@ int V4L2Subdevice::setFormat(unsigned int pad, V4L2SubdeviceFormat *format,
>         subdevFmt.format.height = format->size.height;
>         subdevFmt.format.code = format->mbus_code;
>         subdevFmt.format.field = V4L2_FIELD_NONE;
> -       fromColorSpace(format->colorSpace, subdevFmt.format);
> +       if (format->colorSpace) {
> +               fromColorSpace(format->colorSpace, subdevFmt.format);
> +
> +               /* The CSC flag is only applicable to source pads. */
> +               if (entity_->pads()[pad]->flags() & MEDIA_PAD_FL_SOURCE)
> +                       subdevFmt.format.flags |= V4L2_MBUS_FRAMEFMT_SET_CSC;
> +       }
>  
>         int ret = ioctl(VIDIOC_SUBDEV_S_FMT, &subdevFmt);
>         if (ret) {
> diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
> index b80ee1cd..5a2d0e5b 100644
> --- a/src/libcamera/v4l2_videodevice.cpp
> +++ b/src/libcamera/v4l2_videodevice.cpp
> @@ -953,7 +953,12 @@ int V4L2VideoDevice::trySetFormatMultiplane(V4L2DeviceFormat *format, bool set)
>         pix->pixelformat = format->fourcc;
>         pix->num_planes = format->planesCount;
>         pix->field = V4L2_FIELD_NONE;
> -       fromColorSpace(format->colorSpace, *pix);
> +       if (format->colorSpace) {
> +               fromColorSpace(format->colorSpace, *pix);
> +
> +               if (caps_.isVideoCapture())
> +                       pix->flags |= V4L2_PIX_FMT_FLAG_SET_CSC;
> +       }
>  
>         ASSERT(pix->num_planes <= std::size(pix->plane_fmt));
>  
> @@ -1023,7 +1028,12 @@ int V4L2VideoDevice::trySetFormatSingleplane(V4L2DeviceFormat *format, bool set)
>         pix->pixelformat = format->fourcc;
>         pix->bytesperline = format->planes[0].bpl;
>         pix->field = V4L2_FIELD_NONE;
> -       fromColorSpace(format->colorSpace, *pix);
> +       if (format->colorSpace) {
> +               fromColorSpace(format->colorSpace, *pix);
> +
> +               if (caps_.isVideoCapture())
> +                       pix->flags |= V4L2_PIX_FMT_FLAG_SET_CSC;
> +       }
>  
>         ret = ioctl(set ? VIDIOC_S_FMT : VIDIOC_TRY_FMT, &v4l2Format);
>         if (ret) {
> -- 
> 2.31.1
>