diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index af46211..b1859f6 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -472,6 +472,23 @@
 }
 
 /**
+ * vb2_fileio_is_active() - return true if fileio is active.
+ * @q:		videobuf queue
+ *
+ * This returns true if read() or write() is used to stream the data
+ * as opposed to stream I/O. This is almost never an important distinction,
+ * except in rare cases. One such case is that using read() or write() to
+ * stream a format using V4L2_FIELD_ALTERNATE is not allowed since there
+ * is no way you can pass the field information of each buffer to/from
+ * userspace. A driver that supports this field format should check for
+ * this in the queue_setup op and reject it if this function returns true.
+ */
+static inline bool vb2_fileio_is_active(struct vb2_queue *q)
+{
+	return q->fileio;
+}
+
+/**
  * vb2_is_busy() - return busy status of the queue
  * @q:		videobuf queue
  *