media: videobuf2: set q->streaming later

Commit a10b2153 ("media: vb2: add (un)prepare_streaming queue ops") moved
up the q->streaming = 1 assignment to before the call to vb2_start_streaming().

This does make sense since q->streaming indicates that VIDIOC_STREAMON is called,
and the call to start_streaming happens either at that time or later if
q->min_buffers_needed > 0. So q->streaming should be 1 before start_streaming
is called.

However, it turned out that some drivers use vb2_is_streaming() in buf_queue,
and if q->min_buffers_needed == 0, then that will now return true instead of
false.

So for the time being revert to the original behavior.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Fixes: a10b2153 ("media: vb2: add (un)prepare_streaming queue ops")
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Tested-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/common/videobuf2/videobuf2-core.c

@@ -2149,8 +2149,6 @@ int vb2_core_streamon(struct vb2_queue *q, unsigned int type)
 	if (ret)
 		return ret;
 
-	q->streaming = 1;
-
 	/*
 	 * Tell driver to start streaming provided sufficient buffers
 	 * are available.
@@ -2161,12 +2159,13 @@ int vb2_core_streamon(struct vb2_queue *q, unsigned int type)
 			goto unprepare;
 	}
 
+	q->streaming = 1;
+
 	dprintk(q, 3, "successful\n");
 	return 0;
 
 unprepare:
 	call_void_qop(q, unprepare_streaming, q);
-	q->streaming = 0;
 	return ret;
 }
 EXPORT_SYMBOL_GPL(vb2_core_streamon);