Documentation/media/uapi/v4l/vidioc-enumaudioout.rst

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 .. _VIDIOC_ENUMAUDOUT:
   4
   5 ***********************
   6 ioctl VIDIOC_ENUMAUDOUT
   7 ***********************
   8
   9 Name
  10 ====
  11
  12 VIDIOC_ENUMAUDOUT - Enumerate audio outputs
  13
  14
  15 Synopsis
  16 ========
  17
  18 .. c:function:: int ioctl( int fd, VIDIOC_ENUMAUDOUT, struct v4l2_audioout *argp )
  19     :name: VIDIOC_ENUMAUDOUT
  20
  21
  22 Arguments
  23 =========
  24
  25 ``fd``
  26     File descriptor returned by :ref:`open() <func-open>`.
  27
  28 ``argp``
  29
  30
  31 Description
  32 ===========
  33
  34 To query the attributes of an audio output applications initialize the
  35 ``index`` field and zero out the ``reserved`` array of a struct
  36 :c:type:`v4l2_audioout` and call the ``VIDIOC_G_AUDOUT``
  37 ioctl with a pointer to this structure. Drivers fill the rest of the
  38 structure or return an ``EINVAL`` error code when the index is out of
  39 bounds. To enumerate all audio outputs applications shall begin at index
  40 zero, incrementing by one until the driver returns ``EINVAL``.
  41
  42 .. note::
  43
  44     Connectors on a TV card to loop back the received audio signal
  45     to a sound card are not audio outputs in this sense.
  46
  47 See :ref:`VIDIOC_G_AUDIOout <VIDIOC_G_AUDOUT>` for a description of struct
  48 :c:type:`v4l2_audioout`.
  49
  50
  51 Return Value
  52 ============
  53
  54 On success 0 is returned, on error -1 and the ``errno`` variable is set
  55 appropriately. The generic error codes are described at the
  56 :ref:`Generic Error Codes <gen-errors>` chapter.
  57
  58 EINVAL
  59     The number of the audio output is out of bounds.