|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.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
|post-install sb /sbin/modprobe "-k" "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
| 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.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.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.conf 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, firstname.lastname@example.org, http://as220.org/jb.