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author | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-27 10:45:04 -0300 |
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committer | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-27 10:45:04 -0300 |
commit | 85538b1ad145c67198cb55d02de14ba269cc323d (patch) | |
tree | 409fca93b357839b8c89b7099f2888c087694b64 /Documentation/media/uapi/v4l/vidioc-g-priority.rst | |
parent | 9c1958fc326a0a0a533ec8e86ea6fa30977207de (diff) | |
parent | d271d3d9b333c94cd54a12fa506e17772a04617c (diff) |
Merge branch 'topic/docs-next' into v4l_for_linus
* topic/docs-next: (322 commits)
[media] cx23885-cardlist.rst: add a new card
[media] doc-rst: add some needed escape codes
[media] doc-rst: kapi: use :c:func: instead of :cpp:func
doc-rst: kernel-doc: fix a change introduced by mistake
[media] v4l2-ioctl.h add debug info for struct v4l2_ioctl_ops
[media] dvb_ringbuffer.h: some documentation improvements
[media] v4l2-ctrls.h: fully document the header file
[media] doc-rst: Fix some typedef ugly warnings
[media] doc-rst: reorganize the kAPI v4l2 chapters
[media] rename v4l2-framework.rst to v4l2-intro.rst
[media] move V4L2 clocks to a separate .rst file
[media] v4l2-fh.rst: add cross references and markups
[media] v4l2-fh.rst: add fh contents from v4l2-framework.rst
[media] v4l2-fh.h: add documentation for it
[media] v4l2-event.rst: add cross-references and markups
[media] v4l2-event.h: document all functions
[media] v4l2-event.rst: add text from v4l2-framework.rst
[media] v4l2-framework.rst: remove videobuf quick chapter
[media] v4l2-dev: add cross-references and improve markup
[media] doc-rst: move v4l2-dev doc to a separate file
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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 000000000000..9f774ce400a4 --- /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. |