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?
Regards,
Hans
>
> 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
>
