1 files changed, 124 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-audio.rst b/Documentation/userspace-api/media/v4l/vidioc-g-audio.rst
new file mode 100644
index 000000000..bf61db04d
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/vidioc-g-audio.rst
@@ -0,0 +1,124 @@
+.. 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``
+      - Audio capability flags, see :ref:`audio-capability`.
+    * - __u32
+      - ``mode``
+      - Audio mode flags set by drivers and applications (on
+	:ref:`VIDIOC_S_AUDIO <VIDIOC_G_AUDIO>` ioctl), see :ref:`audio-mode`.
+    * - __u32
+      - ``reserved``\ [2]
+      - Reserved for future extensions. Drivers and applications must set
+	the array to zero.
+
+
+.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}|
+
+.. _audio-capability:
+
+.. flat-table:: Audio Capability Flags
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       3 1 4
+
+    * - ``V4L2_AUDCAP_STEREO``
+      - 0x00001
+      - This is a stereo input. The flag is intended to automatically
+	disable stereo recording etc. when the signal is always monaural.
+	The API provides no means to detect if stereo is *received*,
+	unless the audio input belongs to a tuner.
+    * - ``V4L2_AUDCAP_AVL``
+      - 0x00002
+      - Automatic Volume Level mode is supported.
+
+
+.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}|
+
+.. _audio-mode:
+
+.. flat-table:: Audio Mode Flags
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       3 1 4
+
+    * - ``V4L2_AUDMODE_AVL``
+      - 0x00001
+      - AVL mode is on.
+
+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
+    No audio inputs combine with the current video input, or the number
+    of the selected audio input is out of bounds or it does not combine.