diff options
Diffstat (limited to 'Documentation/DocBook/media/v4l/vidioc-query-dv-timings.xml')
| -rw-r--r-- | Documentation/DocBook/media/v4l/vidioc-query-dv-timings.xml | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/Documentation/DocBook/media/v4l/vidioc-query-dv-timings.xml b/Documentation/DocBook/media/v4l/vidioc-query-dv-timings.xml index e9c70a8f3476..0c93677d16b4 100644 --- a/Documentation/DocBook/media/v4l/vidioc-query-dv-timings.xml +++ b/Documentation/DocBook/media/v4l/vidioc-query-dv-timings.xml @@ -60,9 +60,19 @@ input</refpurpose> automatically, similar to sensing the video standard. To do so, applications call <constant>VIDIOC_QUERY_DV_TIMINGS</constant> with a pointer to a &v4l2-dv-timings;. Once the hardware detects the timings, it will fill in the -timings structure. +timings structure.</para> -If the timings could not be detected because there was no signal, then +<para>Please note that drivers shall <emphasis>not</emphasis> switch timings automatically +if new timings are 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_QUERY_DV_TIMINGS</constant>. +The reason is that new timings usually 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_QUERY_DV_TIMINGS</constant>, +and if the detected timings are valid they will have to stop streaming, set the new +timings, allocate new buffers and start streaming again.</para> + +<para>If the timings could not be detected because there was no signal, then <errorcode>ENOLINK</errorcode> is returned. If a signal was detected, but it was unstable and the receiver could not lock to the signal, then <errorcode>ENOLCK</errorcode> is returned. If the receiver could lock to the signal, |