[media] media: vb2: change queue initialization order

This patch changes the order of operations during stream on call. Now the
buffers are first queued to the driver and then the start_streaming method
is called.

This resolves the most common case when the driver needs to know buffer
addresses to enable dma engine and start streaming. Additional parameter
to start_streaming method have been added to simplify drivers code. The
driver are now obliged to check if the number of queued buffers is high
enough to enable hardware streaming. If not - it can return an error. In
such case all the buffers that have been pre-queued are invalidated.

This patch also updates all videobuf2 clients to work properly with the
changed order of operations.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
CC: Pawel Osciak <pawel@osciak.com>
CC: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
CC: Hans Verkuil <hverkuil@xs4all.nl>
CC: Tomasz Stanislawski <t.stanislaws@samsung.com>
CC: Sylwester Nawrocki <s.nawrocki@samsung.com>
CC: Kamil Debski <k.debski@samsung.com>
CC: Jonathan Corbet <corbet@lwn.net>
CC: Josh Wu <josh.wu@atmel.com>
CC: Hans de Goede <hdegoede@redhat.com>
CC: Paul Mundt <lethal@linux-sh.org>
Tested-by: Josh Wu <josh.wu@atmel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 44 insertions, 53 deletions

diff --git a/drivers/media/video/videobuf2-core.c b/drivers/media/video/videobuf2-core.c
index e89fd53a021a..6687ac33726a 100644
--- a/drivers/media/video/videobuf2-core.c
+++ b/drivers/media/video/videobuf2-core.c
@@ -1111,6 +1111,43 @@ int vb2_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b, bool nonblocking)
 EXPORT_SYMBOL_GPL(vb2_dqbuf);
 
 /**
+ * __vb2_queue_cancel() - cancel and stop (pause) streaming
+ *
+ * Removes all queued buffers from driver's queue and all buffers queued by
+ * userspace from videobuf's queue. Returns to state after reqbufs.
+ */
+static void __vb2_queue_cancel(struct vb2_queue *q)
+{
+	unsigned int i;
+
+	/*
+	 * Tell driver to stop all transactions and release all queued
+	 * buffers.
+	 */
+	if (q->streaming)
+		call_qop(q, stop_streaming, q);
+	q->streaming = 0;
+
+	/*
+	 * Remove all buffers from videobuf's list...
+	 */
+	INIT_LIST_HEAD(&q->queued_list);
+	/*
+	 * ...and done list; userspace will not receive any buffers it
+	 * has not already dequeued before initiating cancel.
+	 */
+	INIT_LIST_HEAD(&q->done_list);
+	atomic_set(&q->queued_count, 0);
+	wake_up_all(&q->done_wq);
+
+	/*
+	 * Reinitialize all buffers for next use.
+	 */
+	for (i = 0; i < q->num_buffers; ++i)
+		q->bufs[i]->state = VB2_BUF_STATE_DEQUEUED;
+}
+
+/**
  * vb2_streamon - start streaming
  * @q:		videobuf2 queue
  * @type:	type argument passed from userspace to vidioc_streamon handler
@@ -1118,7 +1155,7 @@ EXPORT_SYMBOL_GPL(vb2_dqbuf);
  * Should be called from vidioc_streamon handler of a driver.
  * This function:
  * 1) verifies current state
- * 2) starts streaming and passes any previously queued buffers to the driver
+ * 2) passes any previously queued buffers to the driver and starts streaming
  *
  * The return values from this function are intended to be directly returned
  * from vidioc_streamon handler in the driver.
@@ -1144,75 +1181,29 @@ int vb2_streamon(struct vb2_queue *q, enum v4l2_buf_type type)
 	}
 
 	/*
-	 * Cannot start streaming on an OUTPUT device if no buffers have
-	 * been queued yet.
+	 * If any buffers were queued before streamon,
+	 * we can now pass them to driver for processing.
 	 */
-	if (V4L2_TYPE_IS_OUTPUT(q->type)) {
-		if (list_empty(&q->queued_list)) {
-			dprintk(1, "streamon: no output buffers queued\n");
-			return -EINVAL;
-		}
-	}
+	list_for_each_entry(vb, &q->queued_list, queued_entry)
+		__enqueue_in_driver(vb);
 
 	/*
 	 * Let driver notice that streaming state has been enabled.
 	 */
-	ret = call_qop(q, start_streaming, q);
+	ret = call_qop(q, start_streaming, q, atomic_read(&q->queued_count));
 	if (ret) {
 		dprintk(1, "streamon: driver refused to start streaming\n");
+		__vb2_queue_cancel(q);
 		return ret;
 	}
 
 	q->streaming = 1;
 
-	/*
-	 * If any buffers were queued before streamon,
-	 * we can now pass them to driver for processing.
-	 */
-	list_for_each_entry(vb, &q->queued_list, queued_entry)
-		__enqueue_in_driver(vb);
-
 	dprintk(3, "Streamon successful\n");
 	return 0;
 }
 EXPORT_SYMBOL_GPL(vb2_streamon);
 
-/**
- * __vb2_queue_cancel() - cancel and stop (pause) streaming
- *
- * Removes all queued buffers from driver's queue and all buffers queued by
- * userspace from videobuf's queue. Returns to state after reqbufs.
- */
-static void __vb2_queue_cancel(struct vb2_queue *q)
-{
-	unsigned int i;
-
-	/*
-	 * Tell driver to stop all transactions and release all queued
-	 * buffers.
-	 */
-	if (q->streaming)
-		call_qop(q, stop_streaming, q);
-	q->streaming = 0;
-
-	/*
-	 * Remove all buffers from videobuf's list...
-	 */
-	INIT_LIST_HEAD(&q->queued_list);
-	/*
-	 * ...and done list; userspace will not receive any buffers it
-	 * has not already dequeued before initiating cancel.
-	 */
-	INIT_LIST_HEAD(&q->done_list);
-	atomic_set(&q->queued_count, 0);
-	wake_up_all(&q->done_wq);
-
-	/*
-	 * Reinitialize all buffers for next use.
-	 */
-	for (i = 0; i < q->num_buffers; ++i)
-		q->bufs[i]->state = VB2_BUF_STATE_DEQUEUED;
-}
 
 /**
  * vb2_streamoff - stop streaming