On Thu, Jun 5, 2014 at 9:23 PM, Laurent Pinchart
<laurent.pinch...@ideasonboard.com> 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.
>
> Signed-off-by: Laurent Pinchart <laurent.pinch...@ideasonboard.com>
> Acked-by: Hans Verkuil <hans.verk...@cisco.com>

Acked-by: Pawel Osciak <pa...@osciak.com>

> ---
>  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))
> --
> 1.8.5.5
>
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