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| author |   Hans Verkuil <hverkuil@xs4all.nl> | 2015-12-24 11:18:10 -0200 |
|---|---|---|
| committer |   Mauro Carvalho Chehab <mchehab@osg.samsung.com> | 2016-02-01 08:14:54 -0200 |
| commit | 49fe73400d94027c9402d8fc11d1f8ed1a5aeb61 (patch) | |
| tree | 72b1055a2e838a28edbd266f5ae78c5df9923ff9 /Documentation/DocBook/media/v4l/vidioc-querystd.xml | |
| parent | [media] media: adv7604: implement get_selection (diff) | |
| download | linux-dev-49fe73400d94027c9402d8fc11d1f8ed1a5aeb61.tar.xz linux-dev-49fe73400d94027c9402d8fc11d1f8ed1a5aeb61.zip | |
[media] DocBook media: make explicit that standard/timings never change automatically
A driver might detect a new standard or DV timings, but it will never change to
those new timings automatically. Instead it will send an event and let the application
take care of it.
Make this explicit in the documentation.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Diffstat (limited to 'Documentation/DocBook/media/v4l/vidioc-querystd.xml')
| -rw-r--r-- | Documentation/DocBook/media/v4l/vidioc-querystd.xml | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/DocBook/media/v4l/vidioc-querystd.xml b/Documentation/DocBook/media/v4l/vidioc-querystd.xml index 222348542182..3ceae35fab03 100644 --- a/Documentation/DocBook/media/v4l/vidioc-querystd.xml +++ b/Documentation/DocBook/media/v4l/vidioc-querystd.xml @@ -59,6 +59,16 @@ 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> +<para>Please note that drivers shall <emphasis>not</emphasis> switch the video standard +automatically if a new video standard is detected. Instead, drivers should send the +<constant>V4L2_EVENT_SOURCE_CHANGE</constant> event (if they support this) and expect +that userspace will take action by calling <constant>VIDIOC_QUERYSTD</constant>. +The reason is that a new video standard can mean different buffer sizes as well, and you +cannot change buffer sizes on the fly. In general, applications that receive the +Source Change event will have to call <constant>VIDIOC_QUERYSTD</constant>, +and if the detected video standard is valid they will have to stop streaming, set the new +standard, allocate new buffers and start streaming again.</para> + </refsect1> <refsect1> |