100 lines
4.2 KiB
Plaintext
100 lines
4.2 KiB
Plaintext
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Building a loadable sound driver
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================================
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Loadable module support in version 3.5 of VoxWare is mostly rewritten since
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the previous version (3.0.1). This means that some things have changed.
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To compile the sound driver as a loadable module you have to perform
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the following steps:
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1) Install modules-1.2.8.tar.gz package (or later if available).
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2a) Check that symbol remap_page_range is defined in linux/init/ksyms.c.
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Insert a line containing "X(remap_page_range)," if required. The driver will
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not load if this line is missing.
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2b) Recompile kernel with soundcard support disabled.
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3) Boot the new kernel.
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4) cd to the sound driver source directory (this directory). It's no
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longer required that the sound driver sources are installed in the
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kernel source tree (linux/drivers/sound). When installing a separately
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distributed sound driver you may install the sources for example to
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/usr/src/sound.
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5) Execute make in the sound driver source directory. Enter
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configuration parameters as described in Readme.cards. Then just wait until
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the driver is compiled OK.
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6) Copy sound.o to the directory where insmod expects to find it.
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("make install" copies it to /lib/modules/misc).
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7) Use command "insmod sound" to load the driver.
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8) The sound driver can be removed using command "rmmod sound".
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Parameters accepted by the loadable sound driver
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================================================
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Setting DMA buffer size
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-----------------------
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The driver allocates a DMA buffer (or two for full duplex devices)
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every time the audio device (/dev/dsp or /dev/audio) is opened
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and frees it when the device is closed. Size of this buffer is defined
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when the driver is configured (the last question). The buffer size
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can be redefined when loading the driver if required (note that this is
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an optional feature which is not normally required). The buffer size
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is redefined by adding dma_pagesize= parameter to the insmod command line.
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For example:
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insmod sound dma_buffsize=32768
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Minimum buffer size is 4096 and the maximum depends on the DMA channe.
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For 8 bit channels (0 to 3) the limit is 64k and for 16 bit ones (5 to 7)
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it's 128k. Driver selects a suitable buffer size automaticly in case
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you try to spesify an invalid size.
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Q: What is the right DMA buffer size?
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A: It depends on the sampling rate, machine speed and the load of the system.
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Large buffers are required on slow machines, when recording/playing CD-quality
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audio or when there are other processes running on the same system. Also
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recording to hard disk is likely to require large buffers.
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Very small buffers are sufficient when you are just playing 8kHz audio files
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on an empty P133 system. Using a 128k byffer just wastes 120k (or 250k)
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of valuable physical RAM memory.
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The right buffer sice can be easily found by making some experiments
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with the dma_buffsize= parameter. I use usually 16k buffers on a DX4/100 system
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and 64k on an old 386 system.
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NOTE! DMA buffers are used only by /dev/audio# and /dev/dsp# devices.
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Other device files don't use them but there are two exceptions:
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GUS driver uses DMA buffers when loading samples to the card.
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Ensoniq SoundScape driver uses them when doanloading the microcode
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file (sndscape.co[012]) to the card. Using large buffers doesn't
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increase performance in these cases.
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Configuring device parameters when loading the driver
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-----------------------------------------------------
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The loadable version of the sound driver accepts now the same
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sound= parameter that has been available in the LILO command line.
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In this way it's possible to change I/O port, IRQ and DMA addresses
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and to enable/disable various cards at load time. Normally
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the driver uses the configuration parameters entered when compiling
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and configuring the driver.
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Look at Readme.linux for more info.
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NOTE! This method is not normally required. You should use it only when
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you have to use different configuration than normally. The sound=
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command line parameter is error phrone and not recommended.
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Debugging and tracing
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---------------------
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Modularized sound driver doesn't display messages during initialization as
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the kernel compiled one does. This feature can be turned on by adding
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init_trace=1 to the insmod command line.
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For example:
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insmod sound init_trace=1
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