2026-01-21 18:59:54 +08:00
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.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
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.. c:namespace:: V4L
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.. _VIDIOC_G_OUTPUT:
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**************************************
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ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT
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**************************************
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Name
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====
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VIDIOC_G_OUTPUT - VIDIOC_S_OUTPUT - Query or select the current video output
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Synopsis
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========
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.. c:macro:: VIDIOC_G_OUTPUT
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``int ioctl(int fd, VIDIOC_G_OUTPUT, int *argp)``
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.. c:macro:: VIDIOC_S_OUTPUT
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``int ioctl(int fd, VIDIOC_S_OUTPUT, int *argp)``
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Arguments
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=========
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``fd``
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File descriptor returned by :c:func:`open()`.
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``argp``
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Pointer to an integer with output index.
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Description
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===========
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To query the current video output applications call the
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:ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a pointer to an integer where the driver
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stores the number of the output, as in the struct
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:c:type:`v4l2_output` ``index`` field. This ioctl will
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fail only when there are no video outputs, returning the ``EINVAL`` error
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code.
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To select a video output applications store the number of the desired
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output in an integer and call the :ref:`VIDIOC_S_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a
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pointer to this integer. Side effects are possible. For example outputs
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may support different video standards, so the driver may implicitly
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2026-01-29 22:25:33 +08:00
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switch the current standard. Because of these possible side
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2026-01-21 18:59:54 +08:00
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effects applications must select an output before querying or
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negotiating any other parameters.
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Information about video outputs is available using the
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:ref:`VIDIOC_ENUMOUTPUT` ioctl.
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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EINVAL
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The number of the video output is out of bounds, or there are no
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video outputs at all.
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