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 .. cpp:function:: int ioctl( int fd, int request, struct v4l2_audioout *argp )
  19
  20
  21 Arguments
  22 =========
  23
  24 ``fd``
  25     File descriptor returned by :ref:`open() <func-open>`.
  26
  27 ``request``
  28     VIDIOC_ENUMAUDOUT
  29
  30 ``argp``
  31
  32
  33 Description
  34 ===========
  35
  36 To query the attributes of an audio output applications initialize the
  37 ``index`` field and zero out the ``reserved`` array of a struct
  38 :ref:`v4l2_audioout <v4l2-audioout>` and call the ``VIDIOC_G_AUDOUT``
  39 ioctl with a pointer to this structure. Drivers fill the rest of the
  40 structure or return an ``EINVAL`` error code when the index is out of
  41 bounds. To enumerate all audio outputs applications shall begin at index
  42 zero, incrementing by one until the driver returns ``EINVAL``.
  43
  44 .. note:: 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 :ref:`v4l2_audioout <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.