.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later .. c:namespace:: V4L .. _VIDIOC_ENUMAUDOUT: *********************** ioctl VIDIOC_ENUMAUDOUT *********************** Name ==== VIDIOC_ENUMAUDOUT - Enumerate audio outputs Synopsis ======== .. c:macro:: VIDIOC_ENUMAUDOUT ``int ioctl(int fd, VIDIOC_ENUMAUDOUT, struct v4l2_audioout *argp)`` Arguments ========= ``fd`` File descriptor returned by :c:func:`open()`. ``argp`` Pointer to struct :c:type:`v4l2_audioout`. Description =========== To query the attributes of an audio output applications initialize the ``index`` field and zero out the ``reserved`` array of a struct :c:type:`v4l2_audioout` and call the ``VIDIOC_G_AUDOUT`` ioctl with a pointer to this structure. Drivers fill the rest of the structure or return an ``EINVAL`` error code when the index is out of bounds. To enumerate all audio outputs applications shall begin at index zero, incrementing by one until the driver returns ``EINVAL``. .. note:: Connectors on a TV card to loop back the received audio signal to a sound card are not audio outputs in this sense. See :ref:`VIDIOC_G_AUDIOout <VIDIOC_G_AUDOUT>` for a description of struct :c:type:`v4l2_audioout`. 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 The number of the audio output is out of bounds.