mirror of https://gitee.com/openkylin/linux.git
62 lines
1.4 KiB
ReStructuredText
62 lines
1.4 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
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.. _VIDIOC_ENUMAUDOUT:
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***********************
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ioctl VIDIOC_ENUMAUDOUT
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***********************
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Name
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====
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VIDIOC_ENUMAUDOUT - Enumerate audio outputs
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Synopsis
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========
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.. c:function:: int ioctl( int fd, int request, struct v4l2_audioout *argp )
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Arguments
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=========
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``fd``
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File descriptor returned by :ref:`open() <func-open>`.
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``request``
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VIDIOC_ENUMAUDOUT
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``argp``
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Description
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===========
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To query the attributes of an audio output applications initialize the
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``index`` field and zero out the ``reserved`` array of a struct
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:ref:`v4l2_audioout <v4l2-audioout>` and call the ``VIDIOC_G_AUDOUT``
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ioctl with a pointer to this structure. Drivers fill the rest of the
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structure or return an ``EINVAL`` error code when the index is out of
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bounds. To enumerate all audio outputs applications shall begin at index
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zero, incrementing by one until the driver returns ``EINVAL``.
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.. note::
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Connectors on a TV card to loop back the received audio signal
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to a sound card are not audio outputs in this sense.
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See :ref:`VIDIOC_G_AUDIOout <VIDIOC_G_AUDOUT>` for a description of struct
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:ref:`v4l2_audioout <v4l2-audioout>`.
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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 audio output is out of bounds.
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