README

		SALSA-Lib - Small ALSA Library
		==============================

GENERAL
-------

SALSA-Lib is a small, light-weight, hot and spicy version of the ALSA
library, mainly for embedded systems with limited resources.
The library is designed to be source-level compatible with ALSA
library API for limited contents.  Most of function calls are inlined,
and accesses directly to the hardware via system calls.
Some components like ALSA sequencer aren't supported, and most of all,
the alsa-lib plugins and configurations are completely dropped.  Thus,
neither dmix nor format conversion is available with SALSA-lib.

The current features are like below:

CONFIG
  o All functions snd_config_*() are replaced with dummy ones since
    SALSA-Lib doesn't support the configuration files.
    The apps accessing config stuff won't work properly as expected.
  o Disabled as default

PCM
  o Supports only the hw layer, i.e. no up/down-mixing, format
    conversion, rate conversion, etc, and no external plug-in
  o Accepts the limited PCM name, "hw", "default", "default:x",
    and "hw:x,y,z"
  o snd_pcm_mmap_read/write*() are declared but not implemented
    (returns -ENXIO)
  o The support of async handlers can be built in via configure
    option, --enable-async.  For simplicity, SALSA-lib supports
    only one async handler per PCM handler.

CONTROL
  o Supports only the hw layer, no plug-in
  o Some H-control functions are not included
  o The support of async handlers via --enable-async as well as
    PCM async handlers.

MIXER
  o No sort with weight as default, sorted in the order of numid
  o Simple-none layer only
  o "Capture Source" isn't split to switches but handled as an enum
    (I personally like this better :)
  o dB support can be selected via configure option
  o No linear <-> log dB conversion

TIMER
  o No query interface (returns errors)
  o No async handler (returns -ENXIO)
  o Disabled as default

RAWMIDI
  o Should work
  o Disabled as default

HWDEP
  o Should work
  o Disabled as default

SEQUENCER
  o All replaced with dummy functions.  The apps using sequencer won't
    work properly.
  o Disabled as default

INSTRUMENT LAYER
  o No APIs are provided

UCM
  o Not supported yet at all

MISC
  o The API functions that are not supported but defined have
    "deprecated" attribute.  You'll get compile warnings when
    compiling the code using such functions.  (The same is true for
    the all components below.)  They are just warnings that you can
    usually ignore.  The warnings are given so that you can find the
    non-functional features easily.  If warnings really matter, remove
    the deprecated attribute via --disable-deprecated configure
    option.


INSTALLATION
------------

Some configure options are available to reduce the binary size.
As default, rawmidi, hwdep, timer, conf and seq components are
disabled.  They can be enabled via --enable-xxx option, such as
--enable-rawmidi.
The PCM and mixer components are enabled as default, and can be
disabled via --disable-pcm and --disable-mixer option, respectively.

The dB range support can be enabled via --enable-tlv option.  It's
disabled as default.  For enabling the floating-point math calculation
used in dB <-> linear conversion for the mixer, pass --enable-float
option as well.

The support for user-space control elements is enabled as default
to keep the compatibility with the older salsa-lib releases.  But now
it can be disabled via --disable-user-elem configure option, too.

The async handler support can be enabled via --enable-async option.
It's disabled as default.

With option --enable-libasound, libasound.so will be created as an
opt-in ABI-compatible library with the genuine ALSA-lib.

When --enable-abicheck is given, each open function checks the ABI
compatibility with the installed library.

All these options can be enabled via a single option,
--enable-everything, for your convenience.

For disabling the deprecated attribute for non-working functions (see
the description of "MISC" in the section "GENERAL"), pass
--disable-deprecated option.

For enabling the support for the string buffer with snd_output_*()
function (e.g. used by PulseAudio), pass --enable-output-buffer option.

The alsa-library version to be compatible can be given explicitly via
--with-compat-version option.  As default, 1.0.24 is set.

If the ALSA device files are not in /dev/snd, another directory can be
specified with the --with-alsa-devdir option.

The library is installed as $LIBDIR/libsalsa.so.*.
This package provides also the compatible alsa.m4 and alsa.pc.  If the
other packages can be autoreconf'ed, you'll be able to link libsalsa
as it is.

The C header files are installed into $INCLUDEDIR/alsa.  The
alsa/asoundlib.h should be compatible with the normal alsa-lib's one.


CROSS-COMPILATION
-----------------

For compiling the library with a cross compiler, run like the
following:

	% CC=arm-linux-gcc \
	  ./configure --target=arm-linux --host=i686-linux

Don't forget to add "-linux" to the host option value.  Otherwise
configure script won't detect the host type correctly, and the shared
library won't be built properly.


DOCUMENTATION
-------------

See alsa-lib reference.  It's compatible!


KNOWN PROBLEMS
--------------

- Incomplete MMAP mode

  snd_pcm_mmap_*() are not implemented, and the mmap-mode is less
  tested, so far.

- When built without --enable-output-buffer, the buffer output via 
  snd_output_*() functions doesn't work.  And, the last "close"
  argument in snd_input_stdio_attach() and snd_output_stdio_attach()
  is ignored and the attached IO is always closed.


LICENSE
-------

Distributed under LGPL.  See COPYING file.