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author | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-08 11:40:06 -0300 |
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committer | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-08 11:59:40 -0300 |
commit | 60c2820d0f6d3497975b6488e2599f8f611d8b95 (patch) | |
tree | b3b03707c6438ea9b99cc57e847ebf517f968ab1 /Documentation/media/uapi/v4l/vidioc-querystd.rst | |
parent | a97369b5e21ea9b8b5fef7c0f4f48bbe60c07ca3 (diff) | |
download | op-kernel-dev-60c2820d0f6d3497975b6488e2599f8f611d8b95.zip op-kernel-dev-60c2820d0f6d3497975b6488e2599f8f611d8b95.tar.gz |
doc_rst: rename the media Sphinx suff to Documentation/media
The name of the subsystem is "media", and not "linux_tv". Also,
as we plan to add other stuff there in the future, let's
rename also the media uAPI book to media_uapi, to make it
clearer.
No functional changes.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Diffstat (limited to 'Documentation/media/uapi/v4l/vidioc-querystd.rst')
-rw-r--r-- | Documentation/media/uapi/v4l/vidioc-querystd.rst | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/Documentation/media/uapi/v4l/vidioc-querystd.rst b/Documentation/media/uapi/v4l/vidioc-querystd.rst new file mode 100644 index 0000000..5bf6277 --- /dev/null +++ b/Documentation/media/uapi/v4l/vidioc-querystd.rst @@ -0,0 +1,66 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _VIDIOC_QUERYSTD: + +********************* +ioctl VIDIOC_QUERYSTD +********************* + +Name +==== + +VIDIOC_QUERYSTD - Sense the video standard received by the current input + + +Synopsis +======== + +.. cpp:function:: int ioctl( int fd, int request, v4l2_std_id *argp ) + + +Arguments +========= + +``fd`` + File descriptor returned by :ref:`open() <func-open>`. + +``request`` + VIDIOC_QUERYSTD + +``argp`` + + +Description +=========== + +The hardware may be able to detect the current video standard +automatically. To do so, applications call :ref:`VIDIOC_QUERYSTD` with a +pointer to a :ref:`v4l2_std_id <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. 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. + +Please note that drivers shall *not* switch the video standard +automatically if a new video standard is detected. Instead, drivers +should send the ``V4L2_EVENT_SOURCE_CHANGE`` event (if they support +this) and expect that userspace will take action by calling +:ref:`VIDIOC_QUERYSTD`. 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 :ref:`VIDIOC_QUERYSTD`, 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. + + +Return Value +============ + +On success 0 is returned, on error -1 and the ``errno`` variable is set +appropriately. The generic error codes are described at the +:ref:`Generic Error Codes <gen-errors>` chapter. + +ENODATA + Standard video timings are not supported for this input or output. |