ioctl VIDIOC_ENUMAUDIO &manvol; VIDIOC_ENUMAUDIO Enumerate audio inputs int ioctl int fd int request struct v4l2_audio *argp fd &fd; request VIDIOC_ENUMAUDIO argp To query the attributes of an audio input applications initialize the index field and zero out the reserved array of a &v4l2-audio; and call the VIDIOC_ENUMAUDIO ioctl with a pointer to this structure. Drivers fill the rest of the structure or return an &EINVAL; when the index is out of bounds. To enumerate all audio inputs applications shall begin at index zero, incrementing by one until the driver returns EINVAL. See for a description of &v4l2-audio;. &return-value; EINVAL The number of the audio input is out of bounds, or there are no audio inputs at all and this ioctl is not supported.