path: root/Documentation/sound/alsa/ALSA-Configuration.txt

		Advanced Linux Sound Architecture - Driver
		==========================================
			    Configuration guide


Kernel Configuration
====================

To enable ALSA support you need at least to build the kernel with
primary sound card support (CONFIG_SOUND).  Since ALSA can emulate OSS,
you don't have to choose any of the OSS modules.

Enable "OSS API emulation" (CONFIG_SND_OSSEMUL) and both OSS mixer and
PCM supports if you want to run OSS applications with ALSA.

If you want to support the WaveTable functionality on cards such as
SB Live! then you need to enable "Sequencer support"
(CONFIG_SND_SEQUENCER).

To make ALSA debug messages more verbose, enable the "Verbose printk"
and "Debug" options.  To check for memory leaks, turn on "Debug memory"
too.  "Debug detection" will add checks for the detection of cards.

Please note that all the ALSA ISA drivers support the Linux isapnp API
(if the card supports ISA PnP).  You don't need to configure the cards
using isapnptools.


Creating ALSA devices
=====================

This depends on your distribution, but normally you use the /dev/MAKEDEV
script to create the necessary device nodes.  On some systems you use a
script named 'snddevices'.


Module parameters
=================

The user can load modules with options. If the module supports more than
one card and you have more than one card of the same type then you can
specify multiple values for the option separated by commas.

Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.

  Module snd
  ----------

    The core ALSA module.  It is used by all ALSA card drivers.
    It takes the following options which have global effects.

    major	- major number for sound driver
		- Default: 116
    cards_limit
		- limiting card index for auto-loading (1-8)
		- Default: 1
		- For auto-loading more than one card, specify this
		  option together with snd-card-X aliases.
    device_mode
		- permission mask for dynamic sound device filesystem
		- This is available only when DEVFS is enabled
		- Default: 0666
		- E.g.: device_mode=0660

  
  Module snd-pcm-oss
  ------------------

    The PCM OSS emulation module.
    This module takes options which change the mapping of devices.

    dsp_map	- PCM device number maps assigned to the 1st OSS device.
		- Default: 0
    adsp_map	- PCM device number maps assigned to the 2st OSS device.
		- Default: 1
    nonblock_open
		- Don't block opening busy PCM devices.

    For example, when dsp_map=2, /dev/dsp will be mapped to PCM #2 of
    the card #0.  Similarly, when adsp_map=0, /dev/adsp will be mapped
    to PCM #0 of the card #0.
    For changing the second or later card, specify the option with
    commas, such like "dsp_map=0,1".

    nonblock_open option is used to change the behavior of the PCM
    regarding opening the device.  When this option is non-zero,
    opening a busy OSS PCM device won't be blocked but return
    immediately with EAGAIN (just like O_NONBLOCK flag).
    
  Module snd-rawmidi
  ------------------

    This module takes options which change the mapping of devices.
    similar to those of the snd-pcm-oss module.

    midi_map	- MIDI device number maps assigned to the 1st OSS device.
		- Default: 0
    amidi_map	- MIDI device number maps assigned to the 2st OSS device.
		- Default: 1

  Common parameters for top sound card modules
  --------------------------------------------

    Each of top level sound card module takes the following options.

    index	- index (slot #) of sound card
		- Values: 0 through 7 or negative
		- If nonnegative, assign that index number
                - if negative, interpret as a bitmask of permissible
		  indices; the first free permitted index is assigned
		- Default: -1
    id		- card ID (identifier or name)
		- Can be up to 15 characters long
		- Default: the card type
		- A directory by this name is created und