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Subject: media: videobuf2: Drop minimum allocation requirement of 2 buffers Author: Laurent Pinchart laurent.pinchart+renesas@ideasonboard.com Date: Mon Aug 26 02:24:49 2024 +0300

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@vger.kernel.org Signed-off-by: Laurent Pinchart laurent.pinchart+renesas@ideasonboard.com Reviewed-by: Hans Verkuil hverkuil-cisco@xs4all.nl Acked-by: Tomasz Figa tfiga@chromium.org Link: https://lore.kernel.org/r/20240825232449.25905-1-laurent.pinchart+renesas@id... Signed-off-by: Laurent Pinchart laurent.pinchart@ideasonboard.com

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