[PATCH v3] vb2: Check if there are buffers before streamon

[Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>]

This patch adds a test preventing streamon() if there is no buffer
ready.

Without this patch, a user could call streamon() before
preparing any buffer. This leads to a situation where if he calls
close() before calling streamoff() the device is kept streaming.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
---
v2: Comment by Marek Szyprowski:
Reword error message

v3: Comment by Marek Szyprowski:
Actualy do the reword :)

 drivers/media/v4l2-core/videobuf2-core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 098df28..6409e0a 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1776,6 +1776,11 @@ static int vb2_internal_streamon(struct vb2_queue *q, enum v4l2_buf_type type)
 		return 0;
 	}
 
+	if (!q->num_buffers) {
+		dprintk(1, "streamon: no buffers have been allocated\n");
+		return -EINVAL;
+	}
+
 	/*
 	 * If any buffers were queued before streamon,
 	 * we can now pass them to driver for processing.
-- 
1.8.5.2