vidioc-g-output.rst (1840B)
1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2.. c:namespace:: V4L 3 4.. _VIDIOC_G_OUTPUT: 5 6************************************** 7ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT 8************************************** 9 10Name 11==== 12 13VIDIOC_G_OUTPUT - VIDIOC_S_OUTPUT - Query or select the current video output 14 15Synopsis 16======== 17 18.. c:macro:: VIDIOC_G_OUTPUT 19 20``int ioctl(int fd, VIDIOC_G_OUTPUT, int *argp)`` 21 22.. c:macro:: VIDIOC_S_OUTPUT 23 24``int ioctl(int fd, VIDIOC_S_OUTPUT, int *argp)`` 25 26Arguments 27========= 28 29``fd`` 30 File descriptor returned by :c:func:`open()`. 31 32``argp`` 33 Pointer to an integer with output index. 34 35Description 36=========== 37 38To query the current video output applications call the 39:ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a pointer to an integer where the driver 40stores the number of the output, as in the struct 41:c:type:`v4l2_output` ``index`` field. This ioctl will 42fail only when there are no video outputs, returning the ``EINVAL`` error 43code. 44 45To select a video output applications store the number of the desired 46output in an integer and call the :ref:`VIDIOC_S_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a 47pointer to this integer. Side effects are possible. For example outputs 48may support different video standards, so the driver may implicitly 49switch the current standard. Because of these possible side 50effects applications must select an output before querying or 51negotiating any other parameters. 52 53Information about video outputs is available using the 54:ref:`VIDIOC_ENUMOUTPUT` ioctl. 55 56Return Value 57============ 58 59On success 0 is returned, on error -1 and the ``errno`` variable is set 60appropriately. The generic error codes are described at the 61:ref:`Generic Error Codes <gen-errors>` chapter. 62 63EINVAL 64 The number of the video output is out of bounds, or there are no 65 video outputs at all.