Configuring Linux to support sound involves the following steps:
Installing the sound card.
Configuring Plug and Play (if applicable).
Configuring and building the kernel for sound support.
Creating the device files.
Booting the Linux kernel and testing the installation.
If you are running Red Hat Linux there is a utility called
sndconfig that in most cases will detect your sound card and
set up all of the necessary configuration files to load the
appropriate sound drivers for your card. If you are running Red Hat I
suggest you try using it. If it works for you then you can skip the
rest of the instructions in this section.
If sndconfig fails, you are using another Linux distribution,
or you want to follow the manual method in order to better understand
what you are doing, then the next sections will cover each of these
steps in detail.
Follow the manufacturer's instructions for installing the hardware or
have your dealer perform the installation.
Older sound cards usually have switch or jumper settings
for IRQ, DMA channel, etc; note down the values used. If you are
unsure, use the factory defaults. Try to avoid conflicts with other
devices (e.g. ethernet cards, SCSI host adaptors, serial and parallel
ports) if possible.
Usually you should use the same I/O port, IRQ, and DMA settings that
work under DOS. In some cases though (particularly with PnP cards) you
may need to use different settings to get things to work under Linux.
Some experimentation may be needed.
Most sound cards now use the Plug and Play protocol to configure
settings for i/o addresses, interrupts, and DMA channels. If you have
one of the older sound cards that uses fixed settings or jumpers, then
you can skip this section.
As of version 2.2 Linux does not yet have full Plug and Play support
in the kernel. The preferred solution is to use the isapnp tools which
ship with most Linux distributions (or you can download them from Red
Hat's web site
http://www.redhat.com/).
First check the documentation for your Linux distribution. It may
already have Plug and Play support set up for you or it may work
slightly differently than described here. If you need to configure it
yourself,the details can be found in the man pages for the isapnp
tools. Briefly the process you would normally follow is:
Use pnpdump to capture the possible settings for all
your Plug and Play devices, saving the result to the file
/etc/isapnp.conf.
Choose settings for the sound card that do not conflict with
any other devices in your system and uncomment the appropriate lines
in /etc/isapnp.conf. Don't forget to uncomment the
(ACT Y) command near the end.
Make sure that isapnp is run when your system boots
up, normally done by one of the startup scripts. Reboot your system or
run isapnp manually.
If for some reason you cannot or do not wish to use the isapnp tools,
there are a couple of other options. If you use the card under
Microsoft Windows 95 or 98, you can use the device manager to set up
the card, then soft boot into Linux using the LOADLIN program. Make
sure Windows and Linux use the same card setup parameters.
If you use the card under DOS, you can use the icu utility
that comes with SoundBlaster16 PnP cards to configure it under DOS,
then soft boot into Linux using the LOADLIN program. Again, make sure
DOS and Linux use the same card setup parameters.
A few of the sound card drivers include the necessary software to
initialize Plug and Play for the card. Check the documentation for
that card's driver for details.
When initially installing Linux you likely used a precompiled
kernel. These kernels often do not provide sound support. It is best
to recompile the kernel yourself with the drivers you need. You may
also want to recompile the kernel in order to upgrade to a newer
version or to free up memory resources by minimizing the size of the
kernel. Later, when your sound card is working, you may wish to
rebuild the kernel sound drivers as modules.
The
Linux Kernel HOWTO should be consulted for the details of
building a kernel. I will just mention here some issues that are
specific to sound cards.
If you have never configured the kernel for sound support before it is
a good idea to read the relevant documentation included with the
kernel sound drivers, particularly information specific to your card
type. The files can be found in the kernel documentation directory,
usually installed in /usr/src/linux/Documentation/sound.
If this directory is missing you likely either have a very old kernel
version or you have not installed the kernel source code.
Follow the usual procedure for building the kernel. There are
currently three interfaces to the configuration process. A graphical
user interface that runs under X11 can be invoked using make
xconfig. A menu-based system that only requires text displays is
available as make menuconfig. The original method, using
make config, offers a simple text-based interface.
When configuring the kernel there will be many choices for selecting
the type of sound card you have and the driver options to use.
The on-line help within the configuration tool should provide
an explanation of what each option is for. Select the appropriate
options to the best of your knowledge.
After configuring the options you should compile and install the new
kernel as per the Kernel HOWTO.
For proper operation, device file entries must be created for the
sound devices. These are normally created for you during installation
of your Linux system. A quick check can be made using the command
listed below. If the output is as shown (the date stamp will vary)
then the device files are almost certainly okay.
Note that having the right device files there doesn't guarantee
anything on its own. The kernel driver must also be loaded or compiled
in before the devices will work (more on that later).
In rare cases, if you believe the device files are wrong, you can
recreate them. Most Linux distributions have a /dev/MAKEDEV
script which can be used for this purpose.
You should now be ready to boot the new kernel and test the sound
drivers. Follow your usual procedure for installing and rebooting the
new kernel (keep the old kernel around in case of problems, of
course).
During booting, check for a message such as the following on powerup
(if they scroll by too quickly to read, you may be able to retrieve
them with the dmesg command):
Sound initialization started
<Sound Blaster 16 (4.13)> at 0x220 irq 5 dma 1,5
<Sound Blaster 16> at 0x330 irq 5 dma 0
<Yamaha OPL3 FM> at 0x388
Sound initialization complete
This should match your sound card type and jumper settings (if any).
Note that the above messages are not displayed when using loadable
sound driver module (unless you enable it, e.g. using insmod sound
trace_init=1).
When the sound driver is linked into the kernel, the Sound
initialization started and Sound initialization complete
messages should be displayed. If they are not printed, it means that
there is no sound driver present in the kernel. In this case you
should check that you actually installed the kernel you compiled when
enabling the sound driver.
If nothing is printed between the Sound initialization
started and the Sound initialization complete lines, it
means that no sound devices were detected. Most probably it means that
you don't have the correct driver enabled, the card is not supported,
the I/O port is bad or that you have a PnP card that has not been
configured.
The driver may also display some error messages and warnings during
boot. Watch for these when booting the first time after configuring
the sound driver.
Next you should check the device file
/dev/sndstat. Reading the sound driver status device file
should provide additional information on whether the sound card driver
initialized properly. Sample output should look something like this:
% cat /dev/sndstat
Sound Driver:3.5.4-960630 (Sat Jan 4 23:56:57 EST 1997 root,
Linux fizzbin 2.0.27 #48 Thu Dec 5 18:24:45 EST 1996 i586)
Kernel: Linux fizzbin 2.0.27 #48 Thu Dec 5 18:24:45 EST 1996 i586
Config options: 0
Installed drivers:
Type 1: OPL-2/OPL-3 FM
Type 2: Sound Blaster
Type 7: SB MPU-401
Card config:
Sound Blaster at 0x220 irq 5 drq 1,5
SB MPU-401 at 0x330 irq 5 drq 0
OPL-2/OPL-3 FM at 0x388 drq 0
Audio devices:
0: Sound Blaster 16 (4.13)
Synth devices:
0: Yamaha OPL-3
Midi devices:
0: Sound Blaster 16
Timers:
0: System clock
Mixers:
0: Sound Blaster
The command above can report some error messages. "No such file or
directory" indicates that you need to create the device files (see
section 4.3). "No such device" means that sound driver is not loaded
or linked into kernel. Go back to section 4.2 to correct this.
If lines in the "Card config:" section of /dev/sndstat are
listed inside parentheses (such as "(SoundBlaster at 0x220 irq 5 drq
1,5)"), it means that this device was configured but not detected.
Now you should be ready to play a simple sound file. Get hold of a
sound sample file, and send it to the sound device as a basic check of
sound output, e.g.
(Make sure you don't omit the ">" in the commands above).
Note that, in general, using cat is not the proper way to
play audio files, it's just a quick check. You'll want to get a proper
sound player program (described later) that will do a better job.
This command will work only if there is at least one device listed in
the audio devices section of /dev/sndstat. If the audio
devices section is empty you should check why the device was not
detected.
If the above commands return "I/O error", you should look at the
end of the kernel messages listed using the "dmesg" command. It's
likely that an error message is printed there. Very often the message
is "Sound: DMA (output) timed out - IRQ/DRQ config error?". The above
message means that the driver didn't get the expected interrupt from
the sound card. In most cases it means that the IRQ or the DMA channel
configured to the driver doesn't work. The best way to get it working
is to try with all possible DMAs and IRQs supported by the device.
Another possible reason is that the device is not compatible with the
device the driver is configured for. This is almost certainly the case
when a supposedly "SoundBlaster (Pro/16) compatible" sound card
doesn't work with the SoundBlaster driver. In this case you should try
to find out the device your sound card is compatible with (by posting
to the comp.os.linux.hardware newsgroup, for example).
Now you can verify sound recording. If you have sound input
capability, you can do a quick test of this using commands such as the
following:
# record 4 seconds of audio from microphone
EDT% dd bs=8k count=4 </dev/audio >sample.au
4+0 records in
4+0 records out
# play back sound
% cat sample.au >/dev/audio
Obviously for this to work you need a microphone connected to the
sound card and you should speak into it. You may also need to obtain a
mixer program to set the microphone as the input device and adjust the
recording gain level.
If these tests pass, you can be reasonably confident that the sound
D/A and A/D hardware and software are working. If you experience
problems, refer to the next section of this document.
If you still encounter problems after following the instructions in
the HOWTO, here are some things to check. The checks are listed in
increasing order of complexity. If a check fails, solve the problem
before moving to the next stage.
Step 1: Make sure you are really running the kernel you compiled.
You can check the date stamp on the kernel to see if you are running
the one that you compiled with sound support. You can do this with the
uname command:
% uname -a
Linux fizzbin 2.2.4 #1 Tue Mar 23 11:23:21 EST 1999 i586 unknown
or by displaying the file /proc/version:
% cat /proc/version
Linux version 2.2.4 (root@fizzbin) (gcc version 2.7.2.3) #1 Tue Mar 23 11:23:21 EST 1999
If the date stamp doesn't seem to match when you compiled the kernel,
then you are running an old kernel. Did you really reboot? If you use
LILO, did you re-install it (typically by running
lilo)? If booting from floppy, did you create a
new boot floppy and use it when booting?
Step 2: Make sure the kernel sound drivers are compiled in.
The easiest way to do this is to check the output of
dev/sndstat as described earlier. If the output is not as
expected then something went wrong with the kernel configuration or
build. Start the installation process again, beginning with
configuration and building of the kernel.
Step 3: Did the kernel detect your sound card during booting?
Make sure that the sound card was detected when the kernel booted. You
should have seen a message on bootup. If the messages scrolled off the
screen, you can usually recall them using the dmesg command:
% dmesg
or
% tail /var/log/messages
If your sound card was not found then something is wrong. Make sure it
really is installed. If the sound card works under DOS then you can be
reasonably confident that the hardware is working, so it is likely a
problem with the kernel configuration. Either you configured your
sound card as the wrong type or wrong parameters, or your sound card
is not compatible with any of the Linux kernel sound card drivers.
One possibility is that your sound card is one of the
compatible type that requires initialization by the DOS
driver. Try booting DOS and loading the vendor supplied sound card
driver. Then soft boot Linux using Control-Alt-Delete. Make
sure that card I/O address, DMA, and IRQ settings for Linux are the
same as used under DOS. Read the Readme.cards file from
the sound driver source distribution for hints on configuring your
card type.
If your sound card is not listed in this document, it is possible that
the Linux drivers do not support it. You can check with some of the
references listed at the end of this document for assistance.
Step 4: Can you read data from the dsp device?
Try reading from the /dev/audio device using the dd
command listed earlier in this document. The command should run
without errors.
If it doesn't work, then chances are that the problem is an IRQ or DMA
conflict or some kind of hardware incompatibility (the device is not
supported by Linux or the driver is configured for a wrong device).
A remote possibility is broken hardware. Try testing the sound card
under DOS, if possible, to eliminate that as a possibility.
When All Else Fails
If you still have problems, here are some final suggestions for things
to try:
carefully re-read this HOWTO document
read the references listed at the end of this document
and the relevant kernel source documentation files
post a question to one of the comp.os.linux or other
Usenet newsgroups (comp.os.linux.hardware is a good choice; because of
the high level of traffic in these groups it helps to put the string
"sound" in the subject header for the article so the right experts
will see it)
Using a web/Usenet search engine with an intelligently selected
search criteria can give very good results quickly. One such choice is
http://www.altavista.digital.com
try using the latest Linux kernel (but only as a last resort,
the latest development kernels can be unstable)
