--- zzzz-none-000/linux-3.10.107/Documentation/DocBook/media/v4l/vidioc-querystd.xml	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/Documentation/DocBook/media/v4l/vidioc-querystd.xml	2021-02-04 17:41:59.000000000 +0000
@@ -54,7 +54,8 @@
 VIDIOC_QUERYSTD</constant> with a pointer to a &v4l2-std-id; type. The
 driver stores here a set of candidates, this can be a single flag or a
 set of supported standards if for example the hardware can only
-distinguish between 50 and 60 Hz systems. When detection is not
+distinguish between 50 and 60 Hz systems. If no signal was detected,
+then the driver will return V4L2_STD_UNKNOWN. When detection is not
 possible or fails, the set must contain all standards supported by the
 current video input or output.</para>