[media] v4l2-mem2mem: set the queue owner field just as vb2_ioctl_reqbufs does

The queue owner will be used by videobuf2 trace events to determine and
record the device minor number. It is set in v4l2_m2m_reqbufs instead of
v4l2_m2m_ioctl_reqbufs because several drivers implement their own
vidioc_reqbufs handlers that still call v4l2_m2m_reqbufs directly.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/v4l2-core/v4l2-mem2mem.c

@@ -357,9 +357,16 @@ int v4l2_m2m_reqbufs(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
 		     struct v4l2_requestbuffers *reqbufs)
 {
 	struct vb2_queue *vq;
+	int ret;
 
 	vq = v4l2_m2m_get_vq(m2m_ctx, reqbufs->type);
-	return vb2_reqbufs(vq, reqbufs);
+	ret = vb2_reqbufs(vq, reqbufs);
+	/* If count == 0, then the owner has released all buffers and he
+	   is no longer owner of the queue. Otherwise we have an owner. */
+	if (ret == 0)
+		vq->owner = reqbufs->count ? file->private_data : NULL;
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(v4l2_m2m_reqbufs);