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65 lines
1.8 KiB
65 lines
1.8 KiB
.. 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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switch the current standard. Because of these possible side |
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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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