From a7a66acb1b95b11cc39cf990947051a0e9a0346a Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Wed, 30 Jun 2021 09:58:23 +0200 Subject: [PATCH] media: videobuf2-core: dequeue if start_streaming fails [ 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 Reviewed-by: Laurent Pinchart Tested-by: Kieran Bingham Fixes: b3379c6201bb ("[media] vb2: only call start_streaming if sufficient buffers are queued") Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Sasha Levin --- drivers/media/v4l2-core/videobuf2-core.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c index b1a4d4e2341b..3ac9f7260e72 100644 --- a/drivers/media/v4l2-core/videobuf2-core.c +++ b/drivers/media/v4l2-core/videobuf2-core.c @@ -1370,6 +1370,7 @@ 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) { @@ -1399,6 +1400,7 @@ 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; @@ -1429,8 +1431,17 @@ 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(1, "qbuf of buffer %d succeeded\n", vb->index); -- 2.20.1