Beyond Linux From Scratch - Version 5.1

Chapter 37. Multimedia Libraries and Drivers

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ALSA Driver-1.0.4

Introduction to ALSA Driver

The ALSA Driver package contains the ALSA sound drivers. These are the next generation of sound drivers for Linux.

Package information

Installation of ALSA Driver

Before installing the ALSA drivers, note that in your kernel configuration you should have Sound Card Support (CONFIG_SOUND) enabled but nothing else in the Sound menu (with the possible exception of TV Card Mixer support.) In particular, you should not have OSS Sound Modules enabled as this will cause problems when loading the ALSA driver modules.

[Note]

Note

Because ALSA drivers are kernel modules, they must be compiled with the same compiler used to compile the kernel.

Install ALSA Driver using the following commands: 

CC=/opt/gcc-2.95.3/bin/gcc ./configure \
    --with-moddir=/lib/modules/`uname -r`/kernel/drivers/sound \
    --with-kernel=/lib/modules/`uname -r`/build \
    --with-sequencer=yes \
    --with-oss=yes \
    --with-isapnp=no \
    --with-cards=all &&
make &&
make install

If this is the first time you have installed the ALSA drivers, you will need to create the /dev entries using the script provided in the ALSA Driver source tree: 

./snddevices

Command explanations

--with-sequencer=yes: This tells the ALSA Driver package to build the sequencer modules. Most people want them so you will usually want to leave it set to yes.

--with-oss=yes: This tells the package to build the OSS/Free emulation modules. Again, most people want this so it's probably best to stick with yes.

--with-isapnp=no: Most sound cards these days are PCI and ISA Plug and Play support isn't needed. If you are using an ISA PnP sound card, it's best to say yes here. If your card is ISA, but not PnP, it is safer to stay with 'no'.

--with-cards=all: You can tell the script just to build the drivers for your particular sound card here. For full information on which drivers are available, see ./configure --help. If you aren't sure which chipset your sound card uses, look at the file CARDS-STATUS in the ALSA Driver source tree. The default specified here will build all drivers.

Configuring ALSA Driver

Config files

/etc/modules.conf

Configuration Information

To configure the ALSA drivers, you need to add some lines to /etc/modules.conf: 

cat >> /etc/modules.conf << "EOF"
alias char-major-14 soundcore
alias char-major-116 snd

alias snd-card-0 snd-[soundcard-name]

alias sound-slot-0 snd-card-0

alias sound-service-0-0 snd-mixer-oss
alias sound-service-0-1 snd-seq-oss
alias sound-service-0-3 snd-pcm-oss
alias sound-service-0-8 snd-seq-midi
EOF

[soundcard-name] needs to be replaced with the driver relevant to your sound card. If you have more than one sound card, you can add additional sections by repeating the above, changing the first 0 to 1 and so on.

After editing /etc/modules.conf you need to run depmod. If the drivers you have compiled are for the version of the kernel you are currently running, simply run: 

depmod

If you are compiling drivers for a different kernel version than those you are running, you will need to use a line similar to: 

depmod -a 2.4.22 -F /boot/System.map-2.4.22

Contents

The ALSA Driver package contains the ALSA sound card drivers and include files.

Description

ALSA sound card drivers

These are kernel modules which provide audio and MIDI functionality to the operating system.

include files

These are installed in /usr/include/sound and are required to compile certain packages such as ALSA Libraries.

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