Documentation/userspace-api/media/v4l/vidioc-g-audio.rst

Source file repositories/reference/linux-study-clean/Documentation/userspace-api/media/v4l/vidioc-g-audio.rst

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Linux kernel
Corpus path
Documentation/userspace-api/media/v4l/vidioc-g-audio.rst
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.rst
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3591 bytes
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Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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Annotated Snippet

.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
.. c:namespace:: V4L

.. _VIDIOC_G_AUDIO:

************************************
ioctl VIDIOC_G_AUDIO, VIDIOC_S_AUDIO
************************************

Name
====

VIDIOC_G_AUDIO - VIDIOC_S_AUDIO - Query or select the current audio input and its attributes

Synopsis
========

.. c:macro:: VIDIOC_G_AUDIO

``int ioctl(int fd, VIDIOC_G_AUDIO, struct v4l2_audio *argp)``

.. c:macro:: VIDIOC_S_AUDIO

``int ioctl(int fd, VIDIOC_S_AUDIO, const struct v4l2_audio *argp)``

Arguments
=========

``fd``
    File descriptor returned by :c:func:`open()`.

``argp``
    Pointer to struct :c:type:`v4l2_audio`.

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

To query the current audio input applications zero out the ``reserved``
array of a struct :c:type:`v4l2_audio` and call the
:ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` ioctl with a pointer to this structure. Drivers fill
the rest of the structure or return an ``EINVAL`` error code when the device
has no audio inputs, or none which combine with the current video input.

Audio inputs have one writable property, the audio mode. To select the
current audio input *and* change the audio mode, applications initialize
the ``index`` and ``mode`` fields, and the ``reserved`` array of a
struct :c:type:`v4l2_audio` structure and call the :ref:`VIDIOC_S_AUDIO <VIDIOC_G_AUDIO>`
ioctl. Drivers may switch to a different audio mode if the request
cannot be satisfied. However, this is a write-only ioctl, it does not
return the actual new audio mode.

.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|

.. c:type:: v4l2_audio

.. flat-table:: struct v4l2_audio
    :header-rows:  0
    :stub-columns: 0
    :widths:       1 1 2

    * - __u32
      - ``index``
      - Identifies the audio input, set by the driver or application.
    * - __u8
      - ``name``\ [32]
      - Name of the audio input, a NUL-terminated ASCII string, for
	example: "Line In". This information is intended for the user,
	preferably the connector label on the device itself.
    * - __u32
      - ``capability``

Annotation

Implementation Notes