alsa-configuration.txt

底层驱动开发

    Module for UART16550A serial MIDI ports.

    port	- port # for UART16550A chip
    irq		- IRQ # for UART16550A chip, -1 = poll mode
    speed	- speed in bauds (9600,19200,38400,57600,115200)
		  38400 = default
    base	- base for divisor in bauds (57600,115200,230400,460800)
		  115200 = default
    outs	- number of MIDI ports in a serial port (1-4)
		  1 = default
    adaptor	- Type of adaptor.
                  0 = Soundcanvas, 1 = MS-124T, 2 = MS-124W S/A,
		  3 = MS-124W M/B, 4 = Generic
    
    Module supports up to 8 cards. This module does not support autoprobe
    thus the main port must be specified!!! Other options are optional.

  Module snd-trident
  ------------------

    Module for Trident 4DWave DX/NX sound cards.
			* Best Union  Miss Melody 4DWave PCI
			* HIS  4DWave PCI
			* Warpspeed  ONSpeed 4DWave PCI
			* AzTech  PCI 64-Q3D
			* Addonics  SV 750
			* CHIC  True Sound 4Dwave
			* Shark  Predator4D-PCI
			* Jaton  SonicWave 4D

    pcm_channels   - max channels (voices) reserved for PCM
    wavetable_size - max wavetable size in kB (4-?kb)

    Module supports up to 8 cards and autoprobe.

    The power-management is supported.

  Module snd-usb-audio
  --------------------

    Module for USB audio and USB MIDI devices.

    vid             - Vendor ID for the device (optional)
    pid             - Product ID for the device (optional)

    This module supports up to 8 cards, autoprobe and hotplugging.

  Module snd-usb-usx2y
  --------------------

    Module for Tascam USB US-122, US-224 and US-428 devices.

    This module supports up to 8 cards, autoprobe and hotplugging.

    Note: you need to load the firmware via usx2yloader utility included
          in alsa-tools and alsa-firmware packages.

  Module snd-via82xx
  ------------------

    Module for AC'97 motherboards based on VIA 82C686A/686B, 8233,
    8233A, 8233C, 8235, 8237 (south) bridge.

    mpu_port	- 0x300,0x310,0x320,0x330, otherwise obtain BIOS setup
		  [VIA686A/686B only]
    joystick	- Enable joystick (default off) [VIA686A/686B only]
    ac97_clock	- AC'97 codec clock base (default 48000Hz)
    dxs_support	- support DXS channels,
		  0 = auto (default), 1 = enable, 2 = disable,
		  3 = 48k only, 4 = no VRA, 5 = enable any sample
		  rate and different sample rates on different
		  channels
		  [VIA8233/C, 8235, 8237 only]
    ac97_quirk  - AC'97 workaround for strange hardware
		  See "AC97 Quirk Option" section below.

    Module supports autoprobe and multiple bus-master chips (max 8).

    Note: on some SMP motherboards like MSI 694D the interrupts might
          not be generated properly.  In such a case, please try to
          set the SMP (or MPS) version on BIOS to 1.1 instead of
          default value 1.4.  Then the interrupt number will be
          assigned under 15. You might also upgrade your BIOS.
    
    Note: VIA8233/5/7 (not VIA8233A) can support DXS (direct sound)
	  channels as the first PCM.  On these channels, up to 4
	  streams can be played at the same time, and the controller
	  can perform sample rate conversion with separate rates for
	  each channel.
	  As default (dxs_support = 0), 48k fixed rate is chosen
	  except for the known devices since the output is often
	  noisy except for 48k on some mother boards due to the
	  bug of BIOS.
	  Please try once dxs_support=5 and if it works on other
	  sample rates (e.g. 44.1kHz of mp3 playback), please let us
	  know the PCI subsystem vendor/device id's (output of
	  "lspci -nv").
	  If dxs_support=5 does not work, try dxs_support=4; if it
	  doesn't work too, try dxs_support=1.  (dxs_support=1 is
	  usually for old motherboards.  The correct implemented
	  board should work with 4 or 5.)  If it still doesn't
	  work and the default setting is ok, dxs_support=3 is the
	  right choice.  If the default setting doesn't work at all,
	  try dxs_support=2 to disable the DXS channels.
	  In any cases, please let us know the result and the
	  subsystem vendor/device ids.  See "Links and Addresses"
	  below.

    Note: for the MPU401 on VIA823x, use snd-mpu401 driver
	  additionally.  The mpu_port option is for VIA686 chips only.

  Module snd-via82xx-modem
  ------------------------

    Module for VIA82xx AC97 modem

    ac97_clock	- AC'97 codec clock base (default 48000Hz)

    Module supports up to 8 cards.

    Note: The default index value of this module is -2, i.e. the first
          slot is excluded.

  Module snd-virmidi
  ------------------

    Module for virtual rawmidi devices.
    This module creates virtual rawmidi devices which communicate
    to the corresponding ALSA sequencer ports.

    midi_devs	- MIDI devices # (1-8, default=4)
    
    Module supports up to 8 cards.

  Module snd-vx222
  ----------------

    Module for Digigram VX-Pocket VX222, V222 v2 and Mic cards.

    mic		- Enable Microphone on V222 Mic (NYI)
    ibl		- Capture IBL size. (default = 0, minimum size)

    Module supports up to 8 cards.

    When the driver is compiled as a module and the hotplug firmware
    is supported, the firmware data is loaded via hotplug automatically.
    Install the necessary firmware files in alsa-firmware package.
    When no hotplug fw loader is available, you need to load the
    firmware via vxloader utility in alsa-tools package.  To invoke
    vxloader automatically, add the following to /etc/modprobe.conf

	install snd-vx222 /sbin/modprobe --first-time -i snd-vx222 && /usr/bin/vxloader

    (for 2.2/2.4 kernels, add "post-install /usr/bin/vxloader" to
     /etc/modules.conf, instead.)
    IBL size defines the interrupts period for PCM.  The smaller size
    gives smaller latency but leads to more CPU consumption, too.
    The size is usually aligned to 126.  As default (=0), the smallest
    size is chosen.  The possible IBL values can be found in
    /proc/asound/cardX/vx-status proc file.

  Module snd-vxpocket
  -------------------

    Module for Digigram VX-Pocket VX2 and 440 PCMCIA cards.

    ibl      - Capture IBL size. (default = 0, minimum size)

    Module supports up to 8 cards.  The module is compiled only when
    PCMCIA is supported on kernel.

    With the older 2.6.x kernel, to activate the driver via the card
    manager, you'll need to set up /etc/pcmcia/vxpocket.conf.  See the
    sound/pcmcia/vx/vxpocket.c.  2.6.13 or later kernel requires no
    longer require a config file.

    When the driver is compiled as a module and the hotplug firmware
    is supported, the firmware data is loaded via hotplug automatically.
    Install the necessary firmware files in alsa-firmware package.
    When no hotplug fw loader is available, you need to load the
    firmware via vxloader utility in alsa-tools package.

    About capture IBL, see the description of snd-vx222 module.

    Note: the driver is build only when CONFIG_ISA is set.
    
    Note2: snd-vxp440 driver is merged to snd-vxpocket driver since
           ALSA 1.0.10.

  Module snd-ymfpci
  -----------------

    Module for Yamaha PCI chips (YMF72x, YMF74x & YMF75x).

    mpu_port      - 0x300,0x330,0x332,0x334, 0 (disable) by default,
                    1 (auto-detect for YMF744/754 only)
    fm_port       - 0x388,0x398,0x3a0,0x3a8, 0 (disable) by default
                    1 (auto-detect for YMF744/754 only)
    joystick_port - 0x201,0x202,0x204,0x205, 0 (disable) by default,
                    1 (auto-detect)
    rear_switch   - enable shared rear/line-in switch (bool)

    Module supports autoprobe and multiple chips (max 8).

    The power-management is supported.

  Module snd-pdaudiocf
  --------------------

    Module for Sound Core PDAudioCF sound card.

    Note: the driver is build only when CONFIG_ISA is set.


AC97 Quirk Option
=================

The ac97_quirk option is used to enable/override the workaround for
specific devices on drivers for on-board AC'97 controllers like
snd-intel8x0.  Some hardware have swapped output pins between Master
and Headphone, or Surround (thanks to confusion of AC'97
specifications from version to version :-)

The driver provides the auto-detection of known problematic devices,
but some might be unknown or wrongly detected.  In such a case, pass
the proper value with this option.

The following strings are accepted:
    - default	Don't override the default setting
    - disable	Disable the quirk
    - hp_only	Bind Master and Headphone controls as a single control
    - swap_hp	Swap headphone and master controls
    - swap_surround  Swap master and surround controls
    - ad_sharing  For AD1985, turn on OMS bit and use headphone
    - alc_jack	For ALC65x, turn on the jack sense mode
    - inv_eapd	Inverted EAPD implementation
    - mute_led	Bind EAPD bit for turning on/off mute LED

For backward compatibility, the corresponding integer value -1, 0,
... are  accepted, too.

For example, if "Master" volume control has no effect on your device
but only "Headphone" does, pass ac97_quirk=hp_only module option.


Configuring Non-ISAPNP Cards
============================

When the kernel is configured with ISA-PnP support, the modules
supporting the isapnp cards will have module options "isapnp".
If this option is set, *only* the ISA-PnP devices will be probed.
For probing the non ISA-PnP cards, you have to pass "isapnp=0" option
together with the proper i/o and irq configuration.

When the kernel is configured without ISA-PnP support, isapnp option
will be not built in.


Module Autoloading Support
==========================

The ALSA drivers can be loaded automatically on demand by defining
module aliases.  The string 'snd-card-%1' is requested for ALSA native
devices where %i is sound card number from zero to seven.

To auto-load an ALSA driver for OSS services, define the string
'sound-slot-%i' where %i means the slot number for OSS, which
corresponds to the card index of ALSA.  Usually, define this
as the same card module.

An example configuration for a single emu10k1 card is like below:
----- /etc/modprobe.conf
alias snd-card-0 snd-emu10k1
alias sound-slot-0 snd-emu10k1
----- /etc/modprobe.conf

The available number of auto-loaded sound cards depends on the module
option "cards_limit" of snd module.  As default it's set to 1.
To enable the auto-loading of multiple cards, specify the number of
sound cards in that option.

When multiple cards are available, it'd better to specify the index
number for each card via module option, too, so that the order of
cards is kept consistent.

An example configuration for two sound cards is like below:

----- /etc/modprobe.conf
# ALSA portion
options snd cards_limit=2
alias snd-card-0 snd-interwave
alias snd-card-1 snd-ens1371
options snd-interwave index=0
options snd-ens1371 index=1
# OSS/Free portion
alias sound-slot-0 snd-interwave
alias sound-slot-1 snd-ens1371
----- /etc/moprobe.conf

In this example, the interwave card is always loaded as the first card
(index 0) and ens1371 as the second (index 1).


ALSA PCM devices to OSS devices mapping
=======================================

/dev/snd/pcmC0D0[c|p]  -> /dev/audio0 (/dev/audio) -> minor 4
/dev/snd/pcmC0D0[c|p]  -> /dev/dsp0 (/dev/dsp)     -> minor 3
/dev/snd/pcmC0D1[c|p]  -> /dev/adsp0 (/dev/adsp)   -> minor 12
/dev/snd/pcmC1D0[c|p]  -> /dev/audio1              -> minor 4+16 = 20
/dev/snd/pcmC1D0[c|p]  -> /dev/dsp1                -> minor 3+16 = 19
/dev/snd/pcmC1D1[c|p]  -> /dev/adsp1               -> minor 12+16 = 28
/dev/snd/pcmC2D0[c|p]  -> /dev/audio2              -> minor 4+32 = 36
/dev/snd/pcmC2D0[c|p]  -> /dev/dsp2                -> minor 3+32 = 39
/dev/snd/pcmC2D1[c|p]  -> /dev/adsp2               -> minor 12+32 = 44

The first number from /dev/snd/pcmC{X}D{Y}[c|p] expression means
sound card number and second means device number.  The ALSA devices
have either 'c' or 'p' suffix indicating the direction, capture and
playback, respectively.

Please note that the device mapping above may be varied via the module
options of snd-pcm-oss module.


DEVFS support
=============

The ALSA driver fully supports the devfs extension.
You should add lines below to your devfsd.conf file:

LOOKUP snd MODLOAD ACTION snd
REGISTER ^sound/.* PERMISSIONS root.audio 660
REGISTER ^snd/.* PERMISSIONS root.audio 660

Warning: These lines assume that you have the audio group in your system.
         Otherwise replace audio word with another group name (root for
         example).


Proc interfaces (/proc/asound)
==============================

/proc/asound/card#/pcm#[cp]/oss
-------------------------------
  String "erase" - erase all additional informations about OSS applications
  String "<app_name> <fragments> <fragment_size> [<options>]"

   <app_name> - name of application with (higher priority) or without path
   <fragments> - number of fragments or zero if auto
   <fragment_size> - size of fragment in bytes or zero if auto
   <options> - optional parameters
	  - disable   the application tries to open a pcm device for
		      this channel but does not want to use it.
		      (Cause a bug or mmap needs)
		      It's good for Quake etc...
	  - direct    don't use plugins
	  - block     force block mode (rvplayer)
	  - non-block force non-block mode
	  - whole-frag  write only whole fragments (optimization affecting
			playback only)
	  - no-silence  do not fill silence ahead to avoid clicks
	  - buggy-ptr	Returns the whitespace blocks in GETOPTR ioctl
			instead of filled blocks

  Example: echo "x11amp 128 16384" > /proc/asound/card0/pcm0p/oss
           echo "squake 0 0 disable" > /proc/asound/card0/pcm0c/oss
	   echo "rvplayer 0 0 block" > /proc/asound/card0/pcm0p/oss


Early Buffer Allocation
=======================

Some drivers (e.g. hdsp) require the large contiguous buffers, and
sometimes it's too late to find such spaces when the driver module is
actually loaded due to memory fragmentation.  You can pre-allocate the
PCM buffers by loading snd-page-alloc module and write commands to its
proc file in prior, for example, in the early boot stage like
/etc/init.d/*.local scripts.

Reading the proc file /proc/drivers/snd-page-alloc shows the current
usage of page allocation.  In writing, you can send the following
commands to the snd-page-alloc driver:

  - add VENDOR DEVICE MASK SIZE BUFFERS

    VENDOR and DEVICE are PCI vendor and device IDs.  They take
    integer numbers (0x prefix is needed for the hex).
    MASK is the PCI DMA mask.  Pass 0 if not restricted.
    SIZE is the size of each buffer to allocate.  You can pass
    k and m suffix for KB and MB.  The max number is 16MB.
    BUFFERS is the number of buffers to allocate.  It must be greater
    than 0.  The max number is 4.

  - erase

    This will erase the all pre-allocated buffers which are not in
    use.


Links and Addresses
===================

  ALSA project homepage
       http://www.alsa-project.org

  ALSA Bug Tracking System
       https://bugtrack.alsa-project.org/bugs/

  ALSA Developers ML
       mailto:[e-mail]