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.
Some Linux distributions provide a sound driver configuration utility that will detect your sound card and set up all of the necessary configuration files to load the appropriate sound drivers for your card. Red Hat Linux, for example, provides the sndconfig utility. If your distribution provides such a tool I suggest you try using it. If it works for you then you can skip the rest of the instructions in this section.
If this fails 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.
Some sound cards use the ISA Plug and Play protocol to configure settings for i/o addresses, interrupts, and DMA channels. If you have a newer PCI-bus type of sound card, or one of the very old ISA sound cards that uses fixed settings or jumpers, then you can skip this section.
The preferred way to configure Plug and Play cards 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.
True ISA PnP support is implemented in the 2.4 and later kernels. Some of the sound card drivers now support automatically detecting and configuring the cards without the isapnp tools. Check the documentation for the card's driver for details.
You need the appropriate device drivers for your sound card to be present in the kernel. The kernel running on your system may already include the drivers for your sound card. In most cases the drivers would have been built as kernel loadable modules. You can check which drivers are available as modules by looking in the /lib/modules directories. For the 2.4.4 kernel, the sound drivers would normally appear in /lib/modules/2.4.4/kernel/drivers/sound/. If you see the driver(s) for your sound card, you can try using the module directory and skip recompiling the kernel.
If the sound drivers are not already built, you will need to configure and build a new kernel. You can either build the sound drivers into the kernel or build them as kernel loadable modules. In most cases building as modules is preferred, as it allows you to easily experiment with loading different drivers if unsure which one to use and the drivers can be unloaded when not needed, freeing up memory. Building the drivers into the kernel itself may be desirable if you are unfamiliar with kernel modules and want a simpler solution.
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.
% ls -l /dev/dsp crw-rw-rw- 1 root root 14, 3 Apr 25 1995 /dev/dsp
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.
Note that if you are using the devfs filesystem support in the 2.4 kernels, the sound device files are actually found in /dev/sound, but there will be symbolic links to the older devices, such as /dev/dsp.
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).
If you are using loadable kernel modules for sound, you will need to load them using the modprobe command for the appropriate drivers, e.g. run the command modprobe sb for a SoundBlaster card.
After booting, or loading the kernel modules, check for a message such as the following using the dmesg command:
Soundblaster audio driver Copyright (C) by Hannu Savolainen 1993-1996 sb: Creative SB AWE64 PnP detected sb: ISAPnP reports 'Creative SB AWE64 PnP' at i/o 0x220, irq 5, dma 1, 5 SB 4.16 detected OK (220) sb: 1 Soundblaster PnP card(s) found. Crystal 4280/46xx + AC97 Audio, version 1.22.32, 10:28:40 Apr 28 2001 cs46xx: Card found at 0xf4100000 and 0xf4000000, IRQ 11 cs46xx: Thinkpad 600X/A20/T20 (1014:0153) at 0xf4100000/0xf4000000, IRQ 11 ac97_codec: AC97 Audio codec, id: 0x4352:0x5914 (Cirrus Logic CS4297A rev B)
The message should indicate that a sound card was found and match your sound card type and jumper settings (if any). The driver may also display some error messages and warnings if you have incorrectly configured the driver or chosen the wrong one.
Previous versions of this HOWTO suggested checking the output of /dev/sndstat. This is no longer supported in the 2.4 and later kernels.
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.
% cat endoftheworld >/dev/dsp % cat crash.au >/dev/audio
(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.
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).
Some sample sound files can be obtained from ftp://tsx-11.mit.edu/pub/linux/packages/sound/snd-data-0.1.tar.Z>
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 % 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.
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 220.127.116.11) #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?
If you are using kernel loadable modules, use the lsmod command to make sure the modules are loaded:
% /sbin/lsmod Module Size Used by sb 6320 0 (unused) sb_lib 35040 0 [sb] uart401 6544 0 [sb_lib] sound 59888 0 [sb_lib uart401] soundcore 4144 5 [sb_lib sound] isa-pnp 28304 0 [sb] ...
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.
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:
% 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.
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.
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.google.com
try using the latest Linux kernel (but only as a last resort, the latest development kernels can be unstable)
send mail to the author of the sound driver
send mail to the author of the Sound HOWTO
fire up emacs and type Esc-x doctor :-)