media: videobuf2: Add min_reqbufs_allocation field to vb2_queue structure

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Add 'min_reqbufs_allocation' field in the vb2_queue structure so drivers
can specify the minimum number of buffers to allocate when calling
VIDIOC_REQBUFS.
When initializing the queue, v4l2 core makes sure that the following
constraints are respected:
- the minimum number of buffers to allocate must be at least 2 because
one buffer is used by the hardware while the other is being processed
by userspace.
-if the driver needs 'min_queued_buffers' in the queue before calling
start_streaming(), then the minimum requirement is 'min_queued_buffers + 1'
to keep at least one buffer available for userspace.

Simplify __vb2_init_fileio() by using 'min_reqbufs_allocation' directly
to avoid duplicating the minimum number of buffers to allocate computation.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

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Benjamin Gaignard 2024-03-14 16:32:19 +01:00 • committed by Hans Verkuil

parent d7cdb5946f

commit 6662edcd32

2 changed files with 37 additions and 16 deletions

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38

drivers/media/common/videobuf2/videobuf2-core.c

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15

include/media/videobuf2-core.h

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