18c2ecf20Sopenharmony_ci.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 28c2ecf20Sopenharmony_ci.. c:namespace:: V4L 38c2ecf20Sopenharmony_ci 48c2ecf20Sopenharmony_ci.. _VIDIOC_G_PRIORITY: 58c2ecf20Sopenharmony_ci 68c2ecf20Sopenharmony_ci****************************************** 78c2ecf20Sopenharmony_ciioctl VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY 88c2ecf20Sopenharmony_ci****************************************** 98c2ecf20Sopenharmony_ci 108c2ecf20Sopenharmony_ciName 118c2ecf20Sopenharmony_ci==== 128c2ecf20Sopenharmony_ci 138c2ecf20Sopenharmony_ciVIDIOC_G_PRIORITY - VIDIOC_S_PRIORITY - Query or request the access priority associated with a file descriptor 148c2ecf20Sopenharmony_ci 158c2ecf20Sopenharmony_ciSynopsis 168c2ecf20Sopenharmony_ci======== 178c2ecf20Sopenharmony_ci 188c2ecf20Sopenharmony_ci.. c:macro:: VIDIOC_G_PRIORITY 198c2ecf20Sopenharmony_ci 208c2ecf20Sopenharmony_ci``int ioctl(int fd, VIDIOC_G_PRIORITY, enum v4l2_priority *argp)`` 218c2ecf20Sopenharmony_ci 228c2ecf20Sopenharmony_ci.. c:macro:: VIDIOC_S_PRIORITY 238c2ecf20Sopenharmony_ci 248c2ecf20Sopenharmony_ci``int ioctl(int fd, VIDIOC_S_PRIORITY, const enum v4l2_priority *argp)`` 258c2ecf20Sopenharmony_ci 268c2ecf20Sopenharmony_ciArguments 278c2ecf20Sopenharmony_ci========= 288c2ecf20Sopenharmony_ci 298c2ecf20Sopenharmony_ci``fd`` 308c2ecf20Sopenharmony_ci File descriptor returned by :c:func:`open()`. 318c2ecf20Sopenharmony_ci 328c2ecf20Sopenharmony_ci``argp`` 338c2ecf20Sopenharmony_ci Pointer to an enum :c:type:`v4l2_priority` type. 348c2ecf20Sopenharmony_ci 358c2ecf20Sopenharmony_ciDescription 368c2ecf20Sopenharmony_ci=========== 378c2ecf20Sopenharmony_ci 388c2ecf20Sopenharmony_ciTo query the current access priority applications call the 398c2ecf20Sopenharmony_ci:ref:`VIDIOC_G_PRIORITY <VIDIOC_G_PRIORITY>` ioctl with a pointer to an enum v4l2_priority 408c2ecf20Sopenharmony_civariable where the driver stores the current priority. 418c2ecf20Sopenharmony_ci 428c2ecf20Sopenharmony_ciTo request an access priority applications store the desired priority in 438c2ecf20Sopenharmony_cian enum v4l2_priority variable and call :ref:`VIDIOC_S_PRIORITY <VIDIOC_G_PRIORITY>` ioctl 448c2ecf20Sopenharmony_ciwith a pointer to this variable. 458c2ecf20Sopenharmony_ci 468c2ecf20Sopenharmony_ci.. c:type:: v4l2_priority 478c2ecf20Sopenharmony_ci 488c2ecf20Sopenharmony_ci.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}| 498c2ecf20Sopenharmony_ci 508c2ecf20Sopenharmony_ci.. flat-table:: enum v4l2_priority 518c2ecf20Sopenharmony_ci :header-rows: 0 528c2ecf20Sopenharmony_ci :stub-columns: 0 538c2ecf20Sopenharmony_ci :widths: 3 1 4 548c2ecf20Sopenharmony_ci 558c2ecf20Sopenharmony_ci * - ``V4L2_PRIORITY_UNSET`` 568c2ecf20Sopenharmony_ci - 0 578c2ecf20Sopenharmony_ci - 588c2ecf20Sopenharmony_ci * - ``V4L2_PRIORITY_BACKGROUND`` 598c2ecf20Sopenharmony_ci - 1 608c2ecf20Sopenharmony_ci - Lowest priority, usually applications running in background, for 618c2ecf20Sopenharmony_ci example monitoring VBI transmissions. A proxy application running 628c2ecf20Sopenharmony_ci in user space will be necessary if multiple applications want to 638c2ecf20Sopenharmony_ci read from a device at this priority. 648c2ecf20Sopenharmony_ci * - ``V4L2_PRIORITY_INTERACTIVE`` 658c2ecf20Sopenharmony_ci - 2 668c2ecf20Sopenharmony_ci - 678c2ecf20Sopenharmony_ci * - ``V4L2_PRIORITY_DEFAULT`` 688c2ecf20Sopenharmony_ci - 2 698c2ecf20Sopenharmony_ci - Medium priority, usually applications started and interactively 708c2ecf20Sopenharmony_ci controlled by the user. For example TV viewers, Teletext browsers, 718c2ecf20Sopenharmony_ci or just "panel" applications to change the channel or video 728c2ecf20Sopenharmony_ci controls. This is the default priority unless an application 738c2ecf20Sopenharmony_ci requests another. 748c2ecf20Sopenharmony_ci * - ``V4L2_PRIORITY_RECORD`` 758c2ecf20Sopenharmony_ci - 3 768c2ecf20Sopenharmony_ci - Highest priority. Only one file descriptor can have this priority, 778c2ecf20Sopenharmony_ci it blocks any other fd from changing device properties. Usually 788c2ecf20Sopenharmony_ci applications which must not be interrupted, like video recording. 798c2ecf20Sopenharmony_ci 808c2ecf20Sopenharmony_ciReturn Value 818c2ecf20Sopenharmony_ci============ 828c2ecf20Sopenharmony_ci 838c2ecf20Sopenharmony_ciOn success 0 is returned, on error -1 and the ``errno`` variable is set 848c2ecf20Sopenharmony_ciappropriately. The generic error codes are described at the 858c2ecf20Sopenharmony_ci:ref:`Generic Error Codes <gen-errors>` chapter. 868c2ecf20Sopenharmony_ci 878c2ecf20Sopenharmony_ciEINVAL 888c2ecf20Sopenharmony_ci The requested priority value is invalid. 898c2ecf20Sopenharmony_ci 908c2ecf20Sopenharmony_ciEBUSY 918c2ecf20Sopenharmony_ci Another application already requested higher priority. 92