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1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later2.. c:namespace:: V4L3 4.. _VIDIOC_G_PRIORITY:5 6******************************************7ioctl VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY8******************************************9 10Name11====12 13VIDIOC_G_PRIORITY - VIDIOC_S_PRIORITY - Query or request the access priority associated with a file descriptor14 15Synopsis16========17 18.. c:macro:: VIDIOC_G_PRIORITY19 20``int ioctl(int fd, VIDIOC_G_PRIORITY, enum v4l2_priority *argp)``21 22.. c:macro:: VIDIOC_S_PRIORITY23 24``int ioctl(int fd, VIDIOC_S_PRIORITY, const enum v4l2_priority *argp)``25 26Arguments27=========28 29``fd``30 File descriptor returned by :c:func:`open()`.31 32``argp``33 Pointer to an enum :c:type:`v4l2_priority` type.34 35Description36===========37 38To query the current access priority applications call the39:ref:`VIDIOC_G_PRIORITY <VIDIOC_G_PRIORITY>` ioctl with a pointer to an enum v4l2_priority40variable where the driver stores the current priority.41 42To request an access priority applications store the desired priority in43an enum v4l2_priority variable and call :ref:`VIDIOC_S_PRIORITY <VIDIOC_G_PRIORITY>` ioctl44with a pointer to this variable.45 46.. c:type:: v4l2_priority47 48.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}|49 50.. flat-table:: enum v4l2_priority51 :header-rows: 052 :stub-columns: 053 :widths: 3 1 454 55 * - ``V4L2_PRIORITY_UNSET``56 - 057 -58 * - ``V4L2_PRIORITY_BACKGROUND``59 - 160 - Lowest priority, usually applications running in background, for61 example monitoring VBI transmissions. A proxy application running62 in user space will be necessary if multiple applications want to63 read from a device at this priority.64 * - ``V4L2_PRIORITY_INTERACTIVE``65 - 266 -67 * - ``V4L2_PRIORITY_DEFAULT``68 - 269 - Medium priority, usually applications started and interactively70 controlled by the user. For example TV viewers, Teletext browsers,71 or just "panel" applications to change the channel or video72 controls. This is the default priority unless an application73 requests another.74 * - ``V4L2_PRIORITY_RECORD``75 - 376 - Highest priority. Only one file descriptor can have this priority,77 it blocks any other fd from changing device properties. Usually78 applications which must not be interrupted, like video recording.79 80Return Value81============82 83On success 0 is returned, on error -1 and the ``errno`` variable is set84appropriately. The generic error codes are described at the85:ref:`Generic Error Codes <gen-errors>` chapter.86 87EINVAL88 The requested priority value is invalid.89 90EBUSY91 Another application already requested higher priority.92