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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-g-priority.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-g-priority.rst')
-rw-r--r-- | Documentation/media/uapi/v4l/vidioc-g-priority.rst | 117 |
1 files changed, 117 insertions, 0 deletions
diff --git a/Documentation/media/uapi/v4l/vidioc-g-priority.rst b/Documentation/media/uapi/v4l/vidioc-g-priority.rst new file mode 100644 index 0000000..9f774ce --- /dev/null +++ b/Documentation/media/uapi/v4l/vidioc-g-priority.rst @@ -0,0 +1,117 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _VIDIOC_G_PRIORITY: + +****************************************** +ioctl VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY +****************************************** + +Name +==== + +VIDIOC_G_PRIORITY - VIDIOC_S_PRIORITY - Query or request the access priority associated with a file descriptor + + +Synopsis +======== + +.. cpp:function:: int ioctl( int fd, int request, enum v4l2_priority *argp ) + +.. cpp:function:: int ioctl( int fd, int request, const enum v4l2_priority *argp ) + + +Arguments +========= + +``fd`` + File descriptor returned by :ref:`open() <func-open>`. + +``request`` + VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY + +``argp`` + Pointer to an enum v4l2_priority type. + + +Description +=========== + +To query the current access priority applications call the +:ref:`VIDIOC_G_PRIORITY <VIDIOC_G_PRIORITY>` ioctl with a pointer to an enum v4l2_priority +variable where the driver stores the current priority. + +To request an access priority applications store the desired priority in +an enum v4l2_priority variable and call :ref:`VIDIOC_S_PRIORITY <VIDIOC_G_PRIORITY>` ioctl +with a pointer to this variable. + + +.. _v4l2-priority: + +.. flat-table:: enum v4l2_priority + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + + - .. row 1 + + - ``V4L2_PRIORITY_UNSET`` + + - 0 + + - + + - .. row 2 + + - ``V4L2_PRIORITY_BACKGROUND`` + + - 1 + + - Lowest priority, usually applications running in background, for + example monitoring VBI transmissions. A proxy application running + in user space will be necessary if multiple applications want to + read from a device at this priority. + + - .. row 3 + + - ``V4L2_PRIORITY_INTERACTIVE`` + + - 2 + + - + + - .. row 4 + + - ``V4L2_PRIORITY_DEFAULT`` + + - 2 + + - Medium priority, usually applications started and interactively + controlled by the user. For example TV viewers, Teletext browsers, + or just "panel" applications to change the channel or video + controls. This is the default priority unless an application + requests another. + + - .. row 5 + + - ``V4L2_PRIORITY_RECORD`` + + - 3 + + - Highest priority. Only one file descriptor can have this priority, + it blocks any other fd from changing device properties. Usually + applications which must not be interrupted, like video recording. + + +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. + +EINVAL + The requested priority value is invalid. + +EBUSY + Another application already requested higher priority. |