USB audio surround support

[Hans Petter Selasky]

Hi,

There are patches now in the the USB P4 repository that enables support for 
more than 2 audio channels:

uaudio0: <XXXXXXXXXXXXXXX, class 0/0, rev 1.10/0.10, addr 2> on usbus0
uaudio0: Play: 48000 Hz, 8 ch, 16-bit S-LE PCM format
uaudio0: Record: 48000 Hz, 2 ch, 16-bit S-LE PCM format
uaudio0: No midi sequencer

For FULL speed devices this feature is disabled by default due to high 
bandwidth usage:

use:

sysctl hw.usb.uaudio.default_channels=16

or

echo "hw.usb.uaudio.default_channels=16" >> /boot/loader.conf

To override.

Reference:

http://p4web.freebsd.org/chv.cgi?CH=171845

--HPS