On Tue, Aug 27, 2024 at 11:19:22AM +0200, Hans Verkuil wrote:
> On 8/27/24 11:15, Laurent Pinchart wrote:
> > Hi Hans,
> >
> > Please let me know if you expect a pull request, otherwise I'll consider
> > you will take this in your tree.
>
> Can you add it to your "Miscellaneous V4L2 patches" PR and post a v2
> of that today?
I'd rather not, as I don't want to rebase and retest that one.
I'll send a separate pull request for this patch.
> > On Mon, Aug 26, 2024 at 08:31:13AM +0200, Hans Verkuil wrote:
> >> 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>
> >>
> >>> ---
> >>> 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
--
Regards,
Laurent Pinchart
