[media] DocBook/media/v4l: clarify the QUERYSTD documentation

Explicitly mention that this ioctl should return V4L2_STD_UNKNOWN if
not signal was detected.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Hans Verkuil 2013-05-29 10:19:05 -03:00 committed by Mauro Carvalho Chehab
parent 1a2c6866e3
commit f41c4332cf

View file

@ -54,7 +54,8 @@ standard automatically. To do so, applications call <constant>
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>