Audio Class 1.0 (legacy implementation)

configname: CONFIG_USB_CONFIGFS_F_UAC1_LEGACY

Linux Kernel Configuration
└─>Device Drivers
└─>USB support
└─>USB Gadget Support
└─>Advanced Linux Sound Architecture
└─>Audio Class 1.0 (legacy implementation)
In linux kernel since version 4.2 (release Date: 2015-08-30)  
This Audio function implements 1 AudioControl interface,
1 AudioStreaming Interface each for USB-OUT and USB-IN.
This is a legacy driver and requires a real Audio codec
to be present on the device.