From: Hans Verkuil hverkuil-cisco@xs4all.nl
stable inclusion from linux-4.19.203 commit a351cafd536e9fa8a8d16c7749af97325b6a1fa3
--------------------------------
[ Upstream commit c592b46907adbeb81243f7eb7a468c36692658b8 ]
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: b3379c6201bb ("[media] vb2: only call start_streaming if sufficient buffers are queued") Signed-off-by: Mauro Carvalho Chehab mchehab+huawei@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- drivers/media/common/videobuf2/videobuf2-core.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c index 93d250db0b6f0..50015a2ea5ce0 100644 --- a/drivers/media/common/videobuf2/videobuf2-core.c +++ b/drivers/media/common/videobuf2/videobuf2-core.c @@ -1391,6 +1391,7 @@ static int vb2_start_streaming(struct vb2_queue *q) int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb) { struct vb2_buffer *vb; + enum vb2_buffer_state orig_state; int ret;
if (q->error) { @@ -1420,6 +1421,7 @@ 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; @@ -1450,8 +1452,17 @@ 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(2, "qbuf of buffer %d succeeded\n", vb->index);