Research Pre Audio

This side should cover the audio architecture used on the Palm Pre.

Hardware
The used TWL4030 PMIC covers the audio part. TODO: datasheet available?

Soundcards
root@castle:/var/home/root# aplay -l card 0: mcbsp2 [twl4030-i2s (mcbsp2)], device 0: omap-mcbsp-pcm [omap-mcbsp-pcm] Subdevices: 1/1 Subdevice #0: subdevice #0 card 1: mcbsp3 [btsco (mcbsp3)], device 0: omap-mcbsp-pcm [omap-mcbsp-pcm] Subdevices: 1/1 Subdevice #0: subdevice #0
 * List of PLAYBACK Hardware Devices ****

Scripts
Palm uses scripts to configure the lower levels of the sound system that are executed inside the kernel. Audiod triggers them over a sysfs interface. echo "#list" > /sys/devices/platform/twl4030_audio/scdebug for example lists you all available scripts over the kernel message output which you can view with dmesg. You can also try


 * all
 * 1) volume
 * 2) init

These scripts can be triggered by writing is name as a string into

/sys/devices/platform/twl4030_audio/scrun

A good start to dive into this is sound/arm/omap-twl4030/script.c in the kernel patch from palm.

New scripts are inserted into the kernel list via:

/sys/devices/platform/twl4030_audio/scinit

This is also handled by audiod. The scripts can be found in /etc/audio

strace audiod
this script restarts the audiod with an attached strace which is saved in ./audio.log:

mv /usr/sbin/audiod /usr/sbin/audiod-backup kill $(pidof audiod)
 * 1) !/bin/sh
 * 2) Make sure audiod gets not restarted when we kill it

sleep 2

strace -x -s 10000 -f -F -o audio.log audiod-backup & echo "press any key to return to normal mode" read foo kill $(pidof audiod-backup)

sleep 2

mv /usr/sbin/audiod-backup /usr/sbin/audiod sh /etc/event.d/audiod
 * 1) Bring the system into a useable state again