On 26/08/2024 01:24, Laurent Pinchart wrote:
> When introducing the ability for drivers to indicate the minimum number
> of buffers they require an application to allocate, commit 6662edcd32cc
> ("media: videobuf2: Add min_reqbufs_allocation field to vb2_queue
> structure") also introduced a global minimum of 2 buffers. It turns out
> this breaks the Renesas R-Car VSP test suite, where a test that
> allocates a single buffer fails when two buffers are used.
>
> One may consider debatable whether test suite failures without failures
> in production use cases should be considered as a regression, but
> operation with a single buffer is a valid use case. While full frame
> rate can't be maintained, memory-to-memory devices can still be used
> with a decent efficiency, and requiring applications to allocate
> multiple buffers for single-shot use cases with capture devices would
> just waste memory.
>
> For those reasons, fix the regression by dropping the global minimum of
> buffers. Individual drivers can still set their own minimum.
>
> Fixes: 6662edcd32cc ("media: videobuf2: Add min_reqbufs_allocation field to vb2_queue structure")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
Regards,
Hans
> ---
> drivers/media/common/videobuf2/videobuf2-core.c | 7 -------
> 1 file changed, 7 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index 500a4e0c84ab..29a8d876e6c2 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -2632,13 +2632,6 @@ int vb2_core_queue_init(struct vb2_queue *q)
> if (WARN_ON(q->supports_requests && q->min_queued_buffers))
> return -EINVAL;
>
> - /*
> - * The minimum requirement is 2: one buffer is used
> - * by the hardware while the other is being processed by userspace.
> - */
> - if (q->min_reqbufs_allocation < 2)
> - q->min_reqbufs_allocation = 2;
> -
> /*
> * If the driver needs 'min_queued_buffers' in the queue before
> * calling start_streaming() then the minimum requirement is
>
> base-commit: a043ea54bbb975ca9239c69fd17f430488d33522
