Research Pre Audio

2010-03-29T21:17:11Z

Playya: add script to strace audiod

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 ==
<pre>
root@castle:/var/home/root# aplay -l
**** List of PLAYBACK Hardware Devices ****
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
</pre>

== 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.
<pre>
echo "#list" > /sys/devices/platform/twl4030_audio/scdebug
</pre>
for example lists you all available scripts over the kernel message output which you can view with dmesg. You can also try

<pre>
#all
#volume
#init
</pre>

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

<pre>
/sys/devices/platform/twl4030_audio/scrun
</pre>

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:

<pre>
/sys/devices/platform/twl4030_audio/scinit
</pre>

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:

<pre>
#!/bin/sh
#Make sure audiod gets not restarted when we kill it
mv /usr/sbin/audiod /usr/sbin/audiod-backup
kill $(pidof audiod)

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

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

</pre>

WebOS Internals - User contributions [en]

Research Pre Audio