The usb_as driver is a USBA (Solaris USB Architecture) compliant client
driver that supports the USB Audio Class 1.0 specification.
The usb_as driver processes audio data messages during
play and record and sets sample frequency, precision, encoding and other functions
on request from the USB audio control driver. See usb_ac(7D).
This driver is plumbed under the USB audio control driver and does not
directly interface with the user application.