Re: [PATCH v2] media: v4l2-mem2mem: Don't copy frame flags in v4l2_m2m_buf_copy_metadata()

[Philipp Zabel <p.zabel@pengutronix.de>]

On Mi, 2025-10-15 at 13:01 +0300, Laurent Pinchart wrote:
> The v4l2_m2m_buf_copy_metadata() function takes a boolean
> copy_frame_flags argument. When true, it causes the function to copy the
> V4L2_BUF_FLAG_KEYFRAME, V4L2_BUF_FLAG_BFRAME and V4L2_BUF_FLAG_PFRAME
> flags from the output buffer to the capture buffer.
> 
> There is no use cases in any upstream driver for copying the flags.
> KEY/P/B frames are properties of the bitstream buffer in some formats.
> Once decoded, this is no longer a property of the video frame and should
> be discarded.
> 
> It was considered useful to know if an uncompressed frame was decoded
> from a KEY/P/B compressed frame, and to preserve that information if
> that same uncompressed frame was passed through another M2M device (e.g.
> a scaler). However, the V4L2 documentation makes it clear that the flags
> are meant for compressed frames only.
> 
> Drop the copy_frame_flags argument from v4l2_m2m_buf_copy_metadata().
> The change to drivers was performed with the following Coccinelle
> semantic patch:
> 
> @@
> expression src;
> expression dst;
> expression flag;
> @@
> -       v4l2_m2m_buf_copy_metadata(src, dst, flag);
> +       v4l2_m2m_buf_copy_metadata(src, dst);
> 
> include/media/v4l2-mem2mem.h and drivers/media/v4l2-core/v4l2-mem2mem.c
> have been updated manually.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>

regards
Philipp