[media] uvcvideo: Enable VIDIOC_CREATE_BUFS

This patch enables the ioctl to create additional buffers on the
videobuf2 capture queue.

[laurent.pinchart@ideasonboard.com: Acquire privileges instead of just
checking them in VIDIOC_CREATE_BUFS implementation]
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/usb/uvc/uvc_queue.c

@@ -198,6 +198,18 @@ int uvc_query_buffer(struct uvc_video_queue *queue, struct v4l2_buffer *buf)
 	return ret;
 }
 
+int uvc_create_buffers(struct uvc_video_queue *queue,
+		       struct v4l2_create_buffers *cb)
+{
+	int ret;
+
+	mutex_lock(&queue->mutex);
+	ret = vb2_create_bufs(&queue->queue, cb);
+	mutex_unlock(&queue->mutex);
+
+	return ret;
+}
+
 int uvc_queue_buffer(struct uvc_video_queue *queue, struct v4l2_buffer *buf)
 {
 	int ret;

drivers/media/usb/uvc/uvc_v4l2.c

@@ -1000,6 +1000,17 @@ static long uvc_v4l2_do_ioctl(struct file *file, unsigned int cmd, void *arg)
 		return uvc_query_buffer(&stream->queue, buf);
 	}
 
+	case VIDIOC_CREATE_BUFS:
+	{
+		struct v4l2_create_buffers *cb = arg;
+
+		ret = uvc_acquire_privileges(handle);
+		if (ret < 0)
+			return ret;
+
+		return uvc_create_buffers(&stream->queue, cb);
+	}
+
 	case VIDIOC_QBUF:
 		if (!uvc_has_privileges(handle))
 			return -EBUSY;

drivers/media/usb/uvc/uvcvideo.h

@@ -614,6 +614,8 @@ extern int uvc_alloc_buffers(struct uvc_video_queue *queue,
 extern void uvc_free_buffers(struct uvc_video_queue *queue);
 extern int uvc_query_buffer(struct uvc_video_queue *queue,
 		struct v4l2_buffer *v4l2_buf);
+extern int uvc_create_buffers(struct uvc_video_queue *queue,
+		struct v4l2_create_buffers *v4l2_cb);
 extern int uvc_queue_buffer(struct uvc_video_queue *queue,
 		struct v4l2_buffer *v4l2_buf);
 extern int uvc_dequeue_buffer(struct uvc_video_queue *queue,