Ok guys, sorry about wasting your time, I tried find by myself the audio driver in dmesg, checked the man page and, as you see here, it has no volume control, I checked the 4.4 man pages, and it is the same. At least we now all now what it's all about.
Code:
AOA(4) OpenBSD Programmer's Manual (MacPPC) AOA(4)
NAME
aoa - Apple aoa audio device
SYNOPSIS
aoa* at macobio?
audio* at aoa?
DESCRIPTION
The aoa driver provides support for the audio hardware found in some
macppc machines.
HARDWARE
Machines supported by the aoa driver include:
- PowerMac7,3
- PowerMac10,1
- PowerMac10,2
SEE ALSO
audio(4), intro(4)
HISTORY
The aoa driver first appeared in OpenBSD 3.9.
AUTHORS
The aoa driver was written by Tsubai Masanari and ported to OpenBSD by
Joris Vink.
BUGS
This driver needs more testing.
This manual page needs more precision and detail.
Right now this driver does not support volume control.
OpenBSD 4.3 May 31, 2007