.. Permission is granted to copy, distribute and/or modify this
.. document under the terms of the GNU Free Documentation License,
.. Version 1.1 or any later version published by the Free Software
.. Foundation, with no Invariant Sections, no Front-Cover Texts
.. and no Back-Cover Texts. A copy of the license is included at
.. Documentation/media/uapi/fdl-appendix.rst.
..
.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections

.. _VIDIOC_ENUMAUDOUT:

***********************
ioctl VIDIOC_ENUMAUDOUT
***********************

Name
====

VIDIOC_ENUMAUDOUT - Enumerate audio outputs


Synopsis
========

.. c:function:: int ioctl( int fd, VIDIOC_ENUMAUDOUT, struct v4l2_audioout *argp )
    :name: VIDIOC_ENUMAUDOUT


Arguments
=========

``fd``
    File descriptor returned by :ref:`open() <func-open>`.

``argp``
    Pointer to struct :c:type:`v4l2_audioout`.


Description
===========

To query the attributes of an audio output applications initialize the
``index`` field and zero out the ``reserved`` array of a struct
:c:type:`v4l2_audioout` and call the ``VIDIOC_G_AUDOUT``
ioctl with a pointer to this structure. Drivers fill the rest of the
structure or return an ``EINVAL`` error code when the index is out of
bounds. To enumerate all audio outputs applications shall begin at index
zero, incrementing by one until the driver returns ``EINVAL``.

.. note::

    Connectors on a TV card to loop back the received audio signal
    to a sound card are not audio outputs in this sense.

See :ref:`VIDIOC_G_AUDIOout <VIDIOC_G_AUDOUT>` for a description of struct
:c:type:`v4l2_audioout`.


Return Value
============

On success 0 is returned, on error -1 and the ``errno`` variable is set
appropriately. The generic error codes are described at the
:ref:`Generic Error Codes <gen-errors>` chapter.

EINVAL
    The number of the audio output is out of bounds.