1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2.. c:namespace:: V4L 3 4.. _VIDIOC_ENUMAUDOUT: 5 6*********************** 7ioctl VIDIOC_ENUMAUDOUT 8*********************** 9 10Name 11==== 12 13VIDIOC_ENUMAUDOUT - Enumerate audio outputs 14 15Synopsis 16======== 17 18.. c:macro:: VIDIOC_ENUMAUDOUT 19 20``int ioctl(int fd, VIDIOC_ENUMAUDOUT, struct v4l2_audioout *argp)`` 21 22Arguments 23========= 24 25``fd`` 26 File descriptor returned by :c:func:`open()`. 27 28``argp`` 29 Pointer to struct :c:type:`v4l2_audioout`. 30 31Description 32=========== 33 34To 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`` 37ioctl with a pointer to this structure. Drivers fill the rest of the 38structure or return an ``EINVAL`` error code when the index is out of 39bounds. To enumerate all audio outputs applications shall begin at index 40zero, 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 47See :ref:`VIDIOC_G_AUDIOout <VIDIOC_G_AUDOUT>` for a description of struct 48:c:type:`v4l2_audioout`. 49 50Return Value 51============ 52 53On success 0 is returned, on error -1 and the ``errno`` variable is set 54appropriately. The generic error codes are described at the 55:ref:`Generic Error Codes <gen-errors>` chapter. 56 57EINVAL 58 The number of the audio output is out of bounds. 59