media: vb2: fix VBI/poll regression

commit 58d75f4b1ce26324b4d809b18f94819843a98731 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index a127925c9d61da6f92a93fb49d6e6f01f03e0e25..06faea4d60ee0030fd6f9b6c1e9c7e09c618b5a9 100644 (file)
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -745,6 +745,7 @@ static int __reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
         * to the userspace.
         */
        req->count = allocated_buffers;
+       q->waiting_for_buffers = !V4L2_TYPE_IS_OUTPUT(q->type);
 
        return 0;
 }
@@ -793,6 +794,7 @@ static int __create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create
                memset(q->plane_sizes, 0, sizeof(q->plane_sizes));
                memset(q->alloc_ctx, 0, sizeof(q->alloc_ctx));
                q->memory = create->memory;
+               q->waiting_for_buffers = !V4L2_TYPE_IS_OUTPUT(q->type);
        }
 
        num_buffers = min(create->count, VIDEO_MAX_FRAME - q->num_buffers);
@@ -1447,6 +1449,7 @@ static int vb2_internal_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
         * dequeued in dqbuf.
         */
        list_add_tail(&vb->queued_entry, &q->queued_list);
+       q->waiting_for_buffers = false;
        vb->state = VB2_BUF_STATE_QUEUED;
 
        /*
@@ -1841,6 +1844,7 @@ static int vb2_internal_streamoff(struct vb2_queue *q, enum v4l2_buf_type type)
         * and videobuf, effectively returning control over them to userspace.
         */
        __vb2_queue_cancel(q);
+       q->waiting_for_buffers = !V4L2_TYPE_IS_OUTPUT(q->type);
 
        dprintk(3, "Streamoff successful\n");
        return 0;
@@ -2150,9 +2154,16 @@ 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;
+       /*
+        * For compatibility with vb1: if QBUF hasn't been called yet, then
+        * return POLLERR as well. This only affects capture queues, output
+        * queues will always initialize waiting_for_buffers to false.
+        */
+       if (q->waiting_for_buffers)
                return res | POLLERR;
 
        if (list_empty(&q->done_list))

diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index bef53ce555d2641d9538dad2982856e9677c8dd4..b10682cb138c0c06fde609deb71f916f2cabc70f 100644 (file)
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -329,6 +329,9 @@ struct v4l2_fh;
  * @retry_start_streaming: start_streaming() was called, but there were not enough
  *             buffers queued. If set, then retry calling start_streaming when
  *             queuing a new buffer.
+ * @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
  */
 struct vb2_queue {
@@ -362,6 +365,7 @@ struct vb2_queue {
 
        unsigned int                    streaming:1;
        unsigned int                    retry_start_streaming:1;
+       unsigned int                    waiting_for_buffers:1;
 
        struct vb2_fileio_data          *fileio;
 };