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1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later2.. c:namespace:: V4L3 4.. _VIDIOC_G_OUTPUT:5 6**************************************7ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT8**************************************9 10Name11====12 13VIDIOC_G_OUTPUT - VIDIOC_S_OUTPUT - Query or select the current video output14 15Synopsis16========17 18.. c:macro:: VIDIOC_G_OUTPUT19 20``int ioctl(int fd, VIDIOC_G_OUTPUT, int *argp)``21 22.. c:macro:: VIDIOC_S_OUTPUT23 24``int ioctl(int fd, VIDIOC_S_OUTPUT, int *argp)``25 26Arguments27=========28 29``fd``30 File descriptor returned by :c:func:`open()`.31 32``argp``33 Pointer to an integer with output index.34 35Description36===========37 38To query the current video output applications call the39:ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a pointer to an integer where the driver40stores the number of the output, as in the struct41:c:type:`v4l2_output` ``index`` field. This ioctl will42fail only when there are no video outputs, returning the ``EINVAL`` error43code.44 45To select a video output applications store the number of the desired46output in an integer and call the :ref:`VIDIOC_S_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a47pointer to this integer. Side effects are possible. For example outputs48may support different video standards, so the driver may implicitly49switch the current standard. Because of these possible side50effects applications must select an output before querying or51negotiating any other parameters.52 53Information about video outputs is available using the54:ref:`VIDIOC_ENUMOUTPUT` ioctl.55 56Return Value57============58 59On success 0 is returned, on error -1 and the ``errno`` variable is set60appropriately. The generic error codes are described at the61:ref:`Generic Error Codes <gen-errors>` chapter.62 63EINVAL64 The number of the video output is out of bounds, or there are no65 video outputs at all.66