Adding high definition audio support to FreeBSD

Note to the readers:
This is a log about _currently_ privite _ongoing_ attempt to add high definition audio to freebsd.

The Origin:
I bought a mainboard, Asus P5GD1-PRO, with Intel ICH6 chipset. Unfortunately the onboard audio is not supported by FreeBSD. It is set to HD Audio mode and equipped with an RealTek HD Audio codec ALC861. So I wondered how much effort is needed to make FreeBSD work with it.

Background:
Hardware: AC'97, HD Audio
Software: Open Sound System

Open Sound System:
Defines the architecture of sound for UNIX.

The userspace usage in brief:
Operations via /dev/dsp.

1. Open /dev/dsp to get fd to operate with.
2. ioctl() to set desired channel/capabilities.
3. read()/write() to play/record sound.

(((to be continued)))

Reference:

• Intel High Definition Audio Specification
• Implementation documentation of Intel High definition Audio
• Open Sound System
• FreeBSD Architecture Handbook