media: v4l2-mem2mem: Don't copy frame flags in v4l2_m2m_buf_copy_metadata()

The v4l2_m2m_buf_copy_metadata() function takes a boolean
copy_frame_flags argument. When true, it causes the function to

media: v4l2-mem2mem: Don't copy frame flags in v4l2_m2m_buf_copy_metadata()

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>
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

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