[media] vb2: fix VBI/poll regression

The recent conversion of saa7134 to vb2 unconvered a poll() bug that
broke the teletext applications alevt and mtt. These applications
expect that calling poll() without having called VIDIOC_STREAMON will
cause poll() to return POLLERR. That did not happen in vb2.

This patch fixes that behavior. It also fixes what should happen when
poll() is called when STREAMON is called but no buffers have been
queued. In that case poll() will also return POLLERR, but only for
capture queues since output queues will always return POLLOUT
anyway in that situation.

This brings the vb2 behavior in line with the old videobuf behavior.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 80fa7253e483..2fefcf491aa8 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -380,6 +380,9 @@ struct v4l2_fh;
  * @start_streaming_called: start_streaming() was called successfully and we
  *              started streaming.
  * @error:      a fatal error occurred on the queue
+ * @waiting_for_buffers: used in poll() to check if vb2 is still waiting for
+ *              buffers. Only set for capture queues if qbuf has not yet been
+ *              called since poll() needs to return POLLERR in that situation.
  * @fileio:     file io emulator internal data, used only if emulator is active
  * @threadio:   thread io internal data, used only if thread is active
  */
@@ -417,6 +420,7 @@ struct vb2_queue {
         unsigned int                    streaming:1;
         unsigned int                    start_streaming_called:1;
         unsigned int                    error:1;
+        unsigned int                    waiting_for_buffers:1;
 
         struct vb2_fileio_data          *fileio;
         struct vb2_threadio_data        *threadio;