[9.10 regression] HDA power_save=10

[dgf]

I use an Sony Vaio SZ2M-B, which is a 13" subnotebook. As you may think I hear a "pop" due to power saving, which doesn't annoy me. What annoys me is that through the acpi-driver my notebook has the capability to power down the hole audio device, which saves even MORE power and this works without a hearable noise. In Jaunty I had scripts in /etc/acpi/ac.d and battery.d which did power off my audio, when I was on battery, but these directories seem to be obsoleted in Karmic.
The Idea of powering on the chip by demand is even better, than these scripts, which annoyed me sometimes. So if it is possible to check if the driver sony_laptop is loaded and to check if the file /sys/devices/platform/sony-laptop/audiopower exists you could on some notebooks even more power saving.
One can turn off the audio power by executing "echo 0 > /sys/devices/platform/sony-laptop/audiopower" and turn on by echoing 1 instead of 0.
This has only one disadvantage: turning on and off takes time, which is noticeable, and which might be too much for simple notifications in e.g. pidgin. I estimate the delay to 0.5s.

I don't expect you to implement this, it is just a suggestion. I would be happy if you could just tell me, which file to modify for powering my audiochip totally on demand.

btw. sony_laptop offers powering off more devices, e.g. wwan, bluetooth and cd power.

UPDATE: what I forgot to say. powering off the cd is sincy jaunty dangerous, because I needed to unload the driver, which is now build into the kernel.

ProblemType: Bug
AplayDevices:
 **** List of PLAYBACK Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: STAC92xx Analog [STAC92xx Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
Architecture: i386
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: STAC92xx Analog [STAC92xx Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: lutz 2697 F.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xdc340000 irq 21'
   Mixer name : 'SigmaTel CXD9872RD/K'
   Components : 'HDA:83847661,104d0700,00104201 HDA:14f12bfa,104d0200,00090000'
   Controls : 13
   Simple ctrls : 9
Date: Sat Aug 15 13:23:49 2009
DistroRelease: Ubuntu 9.10
Package: alsa-base 1.0.20+dfsg-1ubuntu4
PackageArchitecture: all
ProcEnviron:
 PATH=(custom, user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-5.24-generic
SourcePackage: alsa-driver
Uname: Linux 2.6.31-5-generic i686