4. Installation

4.1. Installing the Sound Card

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.

4.2. Configuring ISA Plug and Play

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.

4.3. Configuring the Kernel

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.

4.4. Creating the Device Files

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.

4.5. Booting Linux and Testing the Installation

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.

4.6. Troubleshooting

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.