From d0b2f91bede3bd5e3d24dd6803e56eee959c1797 Mon Sep 17 00:00:00 2001 From: André Fabian Silva Delgado Date: Thu, 20 Oct 2016 00:10:27 -0300 Subject: Linux-libre 4.8.2-gnu --- Documentation/media/uapi/v4l/vidioc-querystd.rst | 66 ++++++++++++++++++++++++ 1 file changed, 66 insertions(+) create mode 100644 Documentation/media/uapi/v4l/vidioc-querystd.rst (limited to 'Documentation/media/uapi/v4l/vidioc-querystd.rst') diff --git a/Documentation/media/uapi/v4l/vidioc-querystd.rst b/Documentation/media/uapi/v4l/vidioc-querystd.rst new file mode 100644 index 000000000..b4a4e222c --- /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() `. + +``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 ` 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. + +.. note:: 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 ` chapter. + +ENODATA + Standard video timings are not supported for this input or output. -- cgit v1.2.3-54-g00ecf