How I got ALSA sound drivers kind of working
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- Subject: How I got ALSA sound drivers kind of working
- From: Ross Boylan <RossBoylan@stanfordalumni.org>
- Date: Sat, 23 Dec 2000 01:05:47 -0800
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I recently got sound to come out of my speakers using the alsa
drivers, and I thought it might be useful to share my experiences and
This is not a step by step account. Mostly it focuses on key missteps
or problem areas, in hopes that it will help others. I had the
following documents at hand to guide me:
*Alsa-sound-mini-howto (which is not so mini)
*ALSA Tutorial by Timmy (members.home.com/tdouglas/alsa.html)
*Linux Sound How To (which is NOT oriented to ALSA)
*Sound Blaster AWE 32 How To and various SB AWE docs (which I
eventually decided refer to the OSS light, not ALSA, way)
*Debian docs on building the kernel package
And I'm not going to try to duplicate the info there.
I have a Sound Blaster AWE64. Although it's ISA PNP, I (think) I
disabled the PNP. I put it in awhile ago. I have it set to some
non-standard settings to avoid conflicts elsewhere.
My system is Debian Potato with Helix-Gnome, which means I have a bit of
Problem #1: What packages to get.
Well, I never really figured this out. There are packages with
"driver" and with "modules" which seem to be doing the same thing
(maybe the driver is an older set of names). There are utilities, and
lots of libraries. The ALSA Tutorial by Timmy says you should get
esound-alsa and libesd-alsa0, but then adds that the latter conflicts
with libesd, and many packages depend on libesd.
alsa-modules exist, and look like the right idea. But they only exist
for kernel versions way before the stock potato kernel. Perhaps the
stock kernels in potato didn't have the right sound support options?
Or each flavor needed its own set of drivers and this wasn't feasible?
While doing this potato moved to 2.2.18pre21 kernel. Oddly, there was
a package for this kernel, but only in woody! I tried using it,
Problem #2: You have to build from source.
So I broke down and got the kernel source and kernel package tools,
and built my own kernel.
Trick #3: For Linux 2.2, ALSA requires that you enable
the general sound support, but NONE of the specific sound drivers.
Trick #4: To use sound, you must be in the audio group.
I went straight to the alsa site to get the latest source. I figured
as long as I had to build anyway, I might as well get the latest. I
think woody actually has a packaged source, which is probably a better
way to go. It is not immediately obvious which files one should get
from the alsa site (I went down into the drivers section. I used the
packages for alsaconf and alsa-utils).
My final build of
./configure --with-isapnp=yes --with-debug=full --with-kernel=/usr/local/src/kernel-2.2.18pre21 --with-oss=yes --with-cards=sbawe
./configure -help is well worth study. Also note that, if you're
ambitious, you can try to integrate the modules build with the kernel
build. It's possible some of my false starts were the result of
building against a kernel which I then replaced. You probably don't
want --with-debug, but I was getting desperate.
I then followed the steps for building and installing the modules.
Discovery #5: I was trying to load the module with insmod. modprobe
is the right choice to take care of dependencies. I kept staring at
the unresolved symbols messages from insmod and checking the files and
modules.dep. The errors didn't come from problems with either the
files or the dependencies. The needed modules just weren't in memory.
Trap #6: With #5 out of the way, I saw that everything was loading up
until sbawe itself. For some reason alsaconf had set snd_index to 1.
I changed it to 0, and finally the driver loaded. This might be a bug
in alsa conf.
Trap #7: As the ALSA mini-howto warns, the sound is off unless you
turn it on. They suggest "amixer set PCM 100 unmute". I found I
needed "amixer set Master 100" also.
I have not yet been able to get the sound on when the machine starts.
I edited /etc/modules to load sound, but find I need to start the
gnome mixer to have it on. alsactrl looks as if it's designed to keep
the state at start up, but I haven't been able to get that to work.
Or it's working, but something later (e.g., gnome sessions) turns it off.
Trick #8: The ./snddevices script does not put everything (maybe not
anything) in the audio group. You need to chgrp appropriately so
non-root users in audio can hear.
Discovery #9: ALSA scripts may update modules.conf, accounting for
messages I and others received about modules.dep being out of date
with respect to modules.conf. /etc/init.d/alsa calls
update_modules_conf, which is defined in
/usr/lib/alsa-base/snd-dev-utils to run /sbin/update-modules