1 .. Permission is granted to copy, distribute and/or modify this
2 .. document under the terms of the GNU Free Documentation License,
3 .. Version 1.1 or any later version published by the Free Software
4 .. Foundation, with no Invariant Sections, no Front-Cover Texts
5 .. and no Back-Cover Texts. A copy of the license is included at
6 .. Documentation/media/uapi/fdl-appendix.rst.
8 .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
10 .. _VIDIOC_G_PRIORITY:
12 ******************************************
13 ioctl VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY
14 ******************************************
19 VIDIOC_G_PRIORITY - VIDIOC_S_PRIORITY - Query or request the access priority associated with a file descriptor
25 .. c:function:: int ioctl( int fd, VIDIOC_G_PRIORITY, enum v4l2_priority *argp )
26 :name: VIDIOC_G_PRIORITY
28 .. c:function:: int ioctl( int fd, VIDIOC_S_PRIORITY, const enum v4l2_priority *argp )
29 :name: VIDIOC_S_PRIORITY
36 File descriptor returned by :ref:`open() <func-open>`.
39 Pointer to an enum :c:type:`v4l2_priority` type.
45 To query the current access priority applications call the
46 :ref:`VIDIOC_G_PRIORITY <VIDIOC_G_PRIORITY>` ioctl with a pointer to an enum v4l2_priority
47 variable where the driver stores the current priority.
49 To request an access priority applications store the desired priority in
50 an enum v4l2_priority variable and call :ref:`VIDIOC_S_PRIORITY <VIDIOC_G_PRIORITY>` ioctl
51 with a pointer to this variable.
54 .. c:type:: v4l2_priority
56 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
58 .. flat-table:: enum v4l2_priority
63 * - ``V4L2_PRIORITY_UNSET``
66 * - ``V4L2_PRIORITY_BACKGROUND``
68 - Lowest priority, usually applications running in background, for
69 example monitoring VBI transmissions. A proxy application running
70 in user space will be necessary if multiple applications want to
71 read from a device at this priority.
72 * - ``V4L2_PRIORITY_INTERACTIVE``
75 * - ``V4L2_PRIORITY_DEFAULT``
77 - Medium priority, usually applications started and interactively
78 controlled by the user. For example TV viewers, Teletext browsers,
79 or just "panel" applications to change the channel or video
80 controls. This is the default priority unless an application
82 * - ``V4L2_PRIORITY_RECORD``
84 - Highest priority. Only one file descriptor can have this priority,
85 it blocks any other fd from changing device properties. Usually
86 applications which must not be interrupted, like video recording.
92 On success 0 is returned, on error -1 and the ``errno`` variable is set
93 appropriately. The generic error codes are described at the
94 :ref:`Generic Error Codes <gen-errors>` chapter.
97 The requested priority value is invalid.
100 Another application already requested higher priority.