mirror of
https://github.com/torvalds/linux.git
synced 2024-11-01 09:41:44 +00:00
1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
107 lines
4.6 KiB
Plaintext
107 lines
4.6 KiB
Plaintext
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
|
|
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.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, jb@as220.org, http://as220.org/jb.
|