On 06/06/2014 11:50 AM, Hans de Goede wrote: > Hi, > > On 06/05/2014 02:23 PM, Laurent Pinchart wrote: >> The V4L2 specification states that >> >> "When the application did not call VIDIOC_QBUF or VIDIOC_STREAMON yet >> the poll() function succeeds, but sets the POLLERR flag in the revents >> field." >> >> The vb2_poll() function sets POLLERR when the queued buffers list is >> empty, regardless of whether this is caused by the stream not being >> active yet, or by a transient buffer underrun. >> >> Bring the implementation in line with the specification by returning >> POLLERR only when the queue is not streaming. Buffer underruns during >> streaming are not treated specially anymore and just result in poll() >> blocking until the next event. > > After your patch the implementation is still not inline with the spec, > queuing buffers, then starting a thread doing the poll, then doing the > streamon in the main thread will still cause the poll to return POLLERR, > even though buffers are queued, which according to the spec should be enough > for the poll to block. > > The correct check would be: > > if (list_empty(&q->queued_list) && !vb2_is_streaming(q)) > eturn res | POLLERR; Good catch! I should have seen that :-( v4l2-compliance should certainly be extended to test this as well. Regards, Hans > > Regards, > > Hans > > >> >> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> >> Acked-by: Hans Verkuil <hans.verkuil@xxxxxxxxx> >> --- >> drivers/media/v4l2-core/videobuf2-core.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c >> index 349e659..fd428e0 100644 >> --- a/drivers/media/v4l2-core/videobuf2-core.c >> +++ b/drivers/media/v4l2-core/videobuf2-core.c >> @@ -2533,9 +2533,9 @@ unsigned int vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait) >> } >> >> /* >> - * There is nothing to wait for if no buffers have already been queued. >> + * There is nothing to wait for if the queue isn't streaming. >> */ >> - if (list_empty(&q->queued_list)) >> + if (!vb2_is_streaming(q)) >> return res | POLLERR; >> >> if (list_empty(&q->done_list)) >> -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
