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media: videobuf2-core: dequeue if start_streaming fails

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If a vb2_queue sets q->min_buffers_needed then when the number of
queued buffers reaches q->min_buffers_needed, vb2_core_qbuf() will call
the start_streaming() callback. If start_streaming() returns an error,
then that error was just returned by vb2_core_qbuf(), but the buffer
was still queued. However, userspace expects that if VIDIOC_QBUF fails,
the buffer is returned dequeued.

So if start_streaming() fails, then remove the buffer from the queue,
thus avoiding this unwanted side-effect.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Fixes: b3379c6201 ("[media] vb2: only call start_streaming if sufficient buffers are queued")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
This commit is contained in:
Hans Verkuil 2021-06-30 09:58:23 +02:00 committed by Mauro Carvalho Chehab
parent 76f22c93b2
commit c592b46907
1 changed files with 12 additions and 1 deletions
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13
drivers/media/common/videobuf2/videobuf2-core.c
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@ -1573,6 +1573,7 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
struct media_request *req)
{
struct vb2_buffer *vb;
enum vb2_buffer_state orig_state;
int ret;
if (q->error) {
@ -1673,6 +1674,7 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
* Add to the queued buffers list, a buffer will stay on it until
* dequeued in dqbuf.
*/
orig_state = vb->state;
list_add_tail(&vb->queued_entry, &q->queued_list);
q->queued_count++;
q->waiting_for_buffers = false;
@ -1703,8 +1705,17 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
if (q->streaming && !q->start_streaming_called &&
q->queued_count >= q->min_buffers_needed) {
ret = vb2_start_streaming(q);
if (ret)
if (ret) {
/*
* Since vb2_core_qbuf will return with an error,
* we should return it to state DEQUEUED since
* the error indicates that the buffer wasn't queued.
*/
list_del(&vb->queued_entry);
q->queued_count--;
vb->state = orig_state;
return ret;
}
}
dprintk(q, 2, "qbuf of buffer %d succeeded\n", vb->index);