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.