http://mail-index.netbsd.org/tech-kern/2002/03/04/0005.html
auconv.c: Add conversion functions
audio.c: Sample alignment, calling conversion functions, etc.
audio_if.h: Add four hw_* members to "struct audio_params"
audiovar.h: Add conversion buffers, etc.
auich and uaudio: Add conversion request code to *_set_params().
The changes is to allow some limited mixer manipulation through
the audio device (instead of the mixer device).
This rendered 4 methods in audio_hw_if unused so garbage collect these.
- Change the way attach and open works to allow multiple audio
devices.
- Split the mulaw.c file into two to avoid dragging in mulaw
convertsion when they are not needed. Add 16 bit alaw/mulaw tables.
- Change the way audio properties are gotten.
- Recognize more versions os SoundBlaster.
- It is now possible to handle devices that want "looping" DMA,
e.g. the SoundBlaster correctly. The WSS and SB drivers use this.
To do this several new methods were introduced in audio_hw_if.
- Different silence handling (forced by previous change).
- The audio driver can now be mmap()-ed, but due to problems in
the VM system only for writing for now.
- The OSS (Linux) audio emulation takes advantage of some of the
new features.
fix semantics of AUDIO_WERROR (now returns a count).
Also repair audio driver back to "real-time mode" where user must
provide data quickly enough for real time audio or silence is played
until user catches up. Add optional "play all" mode (additional bit in
mode field) to play all samples provided, with silence when needed to
avoid buffer underrun.
enami