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Diffstat (limited to 'Documentation/sound/oss/README.modules')
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diff --git a/Documentation/sound/oss/README.modules b/Documentation/sound/oss/README.modules new file mode 100644 index 000000000..cdc039421 --- /dev/null +++ b/Documentation/sound/oss/README.modules @@ -0,0 +1,106 @@ +Building a modular sound driver +================================ + + The following information is current as of linux-2.1.85. Check the other +readme files, especially README.OSS, for information not specific to +making sound modular. + + First, configure your kernel. This is an idea of what you should be +setting in the sound section: + +<M> Sound card support + +<M> 100% Sound Blaster compatibles (SB16/32/64, ESS, Jazz16) support + + I have SoundBlaster. Select your card from the list. + +<M> Generic OPL2/OPL3 FM synthesizer support +<M> FM synthesizer (YM3812/OPL-3) support + + If you don't set these, you will probably find you can play .wav files +but not .midi. As the help for them says, set them unless you know your +card does not use one of these chips for FM support. + + Once you are configured, make zlilo, modules, modules_install; reboot. +Note that it is no longer necessary or possible to configure sound in the +drivers/sound dir. Now one simply configures and makes one's kernel and +modules in the usual way. + + Then, add to your /etc/modprobe.d/oss.conf something like: + +alias char-major-14-* sb +install sb /sbin/modprobe -i sb && /sbin/modprobe adlib_card +options sb io=0x220 irq=7 dma=1 dma16=5 mpu_io=0x330 +options adlib_card io=0x388 # FM synthesizer + + Alternatively, if you have compiled in kernel level ISAPnP support: + +alias char-major-14 sb +softdep sb post: adlib_card +options adlib_card io=0x388 + + The effect of this is that the sound driver and all necessary bits and +pieces autoload on demand, assuming you use kerneld (a sound choice) and +autoclean when not in use. Also, options for the device drivers are +set. They will not work without them. Change as appropriate for your card. +If you are not yet using the very cool kerneld, you will have to "modprobe +-k sb" yourself to get things going. Eventually things may be fixed so +that this kludgery is not necessary; for the time being, it seems to work +well. + + Replace 'sb' with the driver for your card, and give it the right +options. To find the filename of the driver, look in +/lib/modules/<kernel-version>/misc. Mine looks like: + +adlib_card.o # This is the generic OPLx driver +opl3.o # The OPL3 driver +sb.o # <<The SoundBlaster driver. Yours may differ.>> +sound.o # The sound driver +uart401.o # Used by sb, maybe other cards + + Whichever card you have, try feeding it the options that would be the +default if you were making the driver wired, not as modules. You can +look at function referred to by module_init() for the card to see what +args are expected. + + Note that at present there is no way to configure the io, irq and other +parameters for the modular drivers as one does for the wired drivers.. One +needs to pass the modules the necessary parameters as arguments, either +with /etc/modprobe.d/*.conf or with command-line args to modprobe, e.g. + +modprobe sb io=0x220 irq=7 dma=1 dma16=5 mpu_io=0x330 +modprobe adlib_card io=0x388 + + recommend using /etc/modprobe.d/*.conf. + +Persistent DMA Buffers: + +The sound modules normally allocate DMA buffers during open() and +deallocate them during close(). Linux can often have problems allocating +DMA buffers for ISA cards on machines with more than 16MB RAM. This is +because ISA DMA buffers must exist below the 16MB boundary and it is quite +possible that we can't find a large enough free block in this region after +the machine has been running for any amount of time. The way to avoid this +problem is to allocate the DMA buffers during module load and deallocate +them when the module is unloaded. For this to be effective we need to load +the sound modules right after the kernel boots, either manually or by an +init script, and keep them around until we shut down. This is a little +wasteful of RAM, but it guarantees that sound always works. + +To make the sound driver use persistent DMA buffers we need to pass the +sound.o module a "dmabuf=1" command-line argument. This is normally done +in /etc/modprobe.d/*.conf files like so: + +options sound dmabuf=1 + +If you have 16MB or less RAM or a PCI sound card, this is wasteful and +unnecessary. It is possible that machine with 16MB or less RAM will find +this option useful, but if your machine is so memory-starved that it +cannot find a 64K block free, you will be wasting even more RAM by keeping +the sound modules loaded and the DMA buffers allocated when they are not +needed. The proper solution is to upgrade your RAM. But you do also have +this improper solution as well. Use it wisely. + + I'm afraid I know nothing about anything but my setup, being more of a +text-mode guy anyway. If you have options for other cards or other helpful +hints, send them to me, Jim Bray, jb@as220.org, http://as220.org/jb. |