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: Jiri Slaby <jslaby@suse.cz>

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index de0e87f0b2c3a833f113121709b9a496d29ef1f3..c96bf9465bafee86a092ed927bcd2129501c75f0 100644 (file)
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -703,6 +703,7 @@ 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;
 }
@@ -751,6 +752,7 @@ 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);
@@ -1371,6 +1373,7 @@ static int __vb2_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;
 
        /*
@@ -1755,6 +1758,7 @@ int vb2_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;
@@ -2040,9 +2044,16 @@ 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 6781258d0b677f4a7092b4d29d0c1c7094e8a8a0..3d4c034b99f091fa1399d2b776739bb2728bec0c 100644 (file)
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -321,6 +321,9 @@ struct v4l2_fh;
  * @done_wq:   waitqueue for processes waiting for buffers ready to be dequeued
  * @alloc_ctx: memory type/allocator-specific contexts for each plane
  * @streaming: current streaming state
+ * @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 {
@@ -353,6 +356,7 @@ struct vb2_queue {
        unsigned int                    plane_sizes[VIDEO_MAX_PLANES];
 
        unsigned int                    streaming:1;
+       unsigned int                    waiting_for_buffers:1;
 
        struct vb2_fileio_data          *fileio;
 };