File descriptor returned by
To query the attributes of an audio output applications
index field and zero out the
reserved array of a struct v4l2_audioout and
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.
On success 0 is returned, on error -1 and the
errno variable is set appropriately:
The number of the audio output is out of bounds, or there are no audio outputs at all and this ioctl is not supported.