Documentation/sound/oss/README.modules - linux-imx - Git at Google


            
            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.
	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.