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 found in the sections below.
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.
snd_pcm_mmap_read/write*()functions are declared but not implemented (returns -ENXIO)
--enable-async. For simplicity, SALSA-lib supports only one async handler per PCM handler.
--enable-asyncas well as PCM async handlers.
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-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.
The PCM chmap API support is also optional, can be enabled via
--enable-abi-compat, libasound.so will be created as an opt-in ABI-compatible library with the genuine ALSA-lib.
--enable-abicheck is given, each open function checks the ABI compatibility with the installed library.
--enable-time64 is passed, the library enforces to use the 64bit timespec and 64bit-compatible PCM ioctls even if the libc is still with 32bit time. It's good for testing the 64bit time support.
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
For enabling the support for the string buffer with
snd_output_*() function (e.g. used by PulseAudio), pass
The alsa-library version to be compatible can be given explicitly via
--with-compat-version option. As default, 1.2.5 is set.
If the ALSA device files are not in /dev/snd, another directory can be specified with the
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.
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.
See alsa-lib reference. It's compatible!
Incomplete MMAP mode
snd_pcm_mmap_*() are only partially 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_output_stdio_attach() is ignored and the attached IO is always closed.
Distributed under LGPL. See COPYING file.