introduction

linux-2.6.15.6

Introduction	Notes on Modular Sound Drivers and Soundcore
Wade Hampton 
2/14/2001

Purpose:  
========
This document provides some general notes on the modular 
sound drivers and their configuration, along with the 
support modules sound.o and soundcore.o.

Note, some of this probably should be added to the Sound-HOWTO!

Note, soundlow.o was present with 2.2 kernels but is not 
required for 2.4.x kernels.  References have been removed
to this.


Copying:
========
none


History:
========
0.1.0  11/20/1998  First version, draft
1.0.0  11/1998     Alan Cox changes, incorporation in 2.2.0
                   as Documentation/sound/oss/Introduction
1.1.0  6/30/1999   Second version, added notes on making the drivers,
                   added info on multiple sound cards of similar types,]
                   added more diagnostics info, added info about esd.
                   added info on OSS and ALSA.
1.1.1  19991031	   Added notes on sound-slot- and sound-service.
			(Alan Cox)
1.1.2  20000920    Modified for Kernel 2.4 (Christoph Hellwig)
1.1.3  20010214    Minor notes and corrections (Wade Hampton)
                   Added examples of sound-slot-0, etc.


Modular Sound Drivers:
======================

Thanks to the GREAT work by Alan Cox ([e-mail]),

[And Oleg Drokin, Thomas Sailer, Andrew Veliath and more than a few 
 others - not to mention Hannu's original code being designed well
 enough to cope with that kind of chopping up](Alan)

the standard Linux kernels support a modular sound driver.  From
Alan's comments in linux/drivers/sound/README.FIRST:

  The modular sound driver patches were funded by Red Hat Software 
  (www.redhat.com). The sound driver here is thus a modified version of 
  Hannu's code. Please bear that in mind when considering the appropriate
  forums for bug reporting.

The modular sound drivers may be loaded via insmod or modprobe.  
To support all the various sound modules, there are two general 
support modules that must be loaded first:
 
   soundcore.o:   Top level handler for the sound system, provides
                  a set of functions for registration of devices
                  by type.

   sound.o:       Common sound functions required by all modules.

For the specific sound modules (e.g., sb.o for the Soundblaster), 
read the documentation on that module to determine what options
are available, for example IRQ, address, DMA.

Warning, the options for different cards sometime use different names 
for the same or a similar feature (dma1= versus dma16=).  As a last 
resort, inspect the code (search for MODULE_PARM).

Notes:

1.  There is a new OpenSource sound driver called ALSA which is
    currently under development:  http://www.alsa-project.org/
    The ALSA drivers support some newer hardware that may not 
    be supported by this sound driver and also provide some 
    additional features.

2.  The commercial OSS driver may be obtained from the site:
    http://www/opensound.com.  This may be used for cards that
    are unsupported by the kernel driver, or may be used
    by other operating systems.  

3.  The enlightenment sound daemon may be used for playing
    multiple sounds at the same time via a single card, eliminating
    some of the requirements for multiple sound card systems.  For
    more information, see:  http://www.tux.org/~ricdude/EsounD.html  
    The "esd" program may be used with the real-player and mpeg 
    players like mpg123 and x11amp.  The newer real-player 
    and some games even include built-in support for ESD!


Building the Modules:
=====================

This document does not provide full details on building the 
kernel, etc.  The notes below apply only to making the kernel
sound modules.   If this conflicts with the kernel's README,
the README takes precedence. 

1.  To make the kernel sound modules, cd to your /usr/src/linux
    directory (typically) and type make config, make menuconfig, 
    or make xconfig (to start the command line, dialog, or x-based
    configuration tool).  

2.  Select the Sound option and a dialog will be displayed.  

3.  Select M (module) for "Sound card support".

4.  Select your sound driver(s) as a module.  For ProAudio, Sound
    Blaster, etc., select M (module) for OSS sound modules.
    [thanks to Marvin Stodolsky <[e-mail]>]A

5.  Make the kernel (e.g., make bzImage), and install the kernel.

6.  Make the modules and install them (make modules; make modules_install).

Note, for 2.5.x kernels, make sure you have the newer module-init-tools 
installed or modules will not be loaded properly.  2.5.x requires an
updated module-init-tools.


Plug and Play (PnP:
===================

If the sound card is an ISA PnP card, isapnp may be used
to configure the card.  See the file isapnp.txt in the 
directory one level up (e.g., /usr/src/linux/Documentation).

Also the 2.4.x kernels provide PnP capabilities, see the 
file NEWS in this directory.

PCI sound cards are highly recommended, as they are far 
easier to configure and from what I have read, they use
less resources and are more CPU efficient.


INSMOD:
=======

If loading via insmod, the common modules must be loaded in the 
order below BEFORE loading the other sound modules.  The card-specific
modules may then be loaded (most require parameters).  For example,
I use the following via a shell script to load my SoundBlaster:

SB_BASE=0x240
SB_IRQ=9
SB_DMA=3
SB_DMA2=5
SB_MPU=0x300
#
echo Starting sound
/sbin/insmod soundcore
/sbin/insmod sound  
#
echo Starting sound blaster....
/sbin/insmod uart401
/sbin/insmod sb io=$SB_BASE irq=$SB_IRQ dma=$SB_DMA dma16=$SB_DMA2 mpu_io=$SB_MP

When using sound as a module, I typically put these commands
in a file such as /root/soundon.sh.


MODPROBE:
=========

If loading via modprobe, these common files are automatically loaded 
when requested by modprobe.  For example, my /etc/modprobe.conf contains:

alias sound sb 
options sb io=0x240 irq=9 dma=3 dma16=5 mpu_io=0x300

All you need to do to load the module is:

	/sbin/modprobe sb


Sound Status:
=============

The status of sound may be read/checked by:
        cat (anyfile).au >/dev/audio

[WWH:  This may not work properly for SoundBlaster PCI 128 cards
such as the es1370/1 (see the es1370/1 files in this directory) 
as they do not automatically support uLaw on /dev/audio.]

The status of the modules and which modules depend on 
which other modules may be checked by:
	/sbin/lsmod

/sbin/lsmod should show something like the following:
	sb                     26280   0 
	uart401                 5640   0  [sb]
	sound                  57112   0  [sb uart401]
	soundcore               1968   8  [sb sound]


Removing Sound: 
=============== 

Sound may be removed by using /sbin/rmmod in the reverse order
in which you load the modules.  Note, if a program has a sound device
open (e.g., xmixer), that module (and the modules on which it 
depends) may not be unloaded.

For example, I use the following to remove my Soundblaster (rmmod
in the reverse order in which I loaded the modules):

/sbin/rmmod sb
/sbin/rmmod uart401
/sbin/rmmod sound
/sbin/rmmod soundcore

When using sound as a module, I typically put these commands
in a script such as /root/soundoff.sh.


Removing Sound for use with OSS: 
================================ 

If you get really stuck or have a card that the kernel modules
will not support, you can get a commercial sound driver from
http://www.opensound.com.  Before loading the commercial sound
driver, you should do the following:

1.  remove sound modules (detailed above)