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88 lines
2.7 KiB
Plaintext
88 lines
2.7 KiB
Plaintext
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Linux sound-driver module
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(c) Peter Trattler
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License: GPL (Gnu Public License)
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Idea:
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I've modified the sources for the sound driver to allow simply insert and
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remove the sound driver from the kernel by calling (only available for Linux)
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insmod /usr/src/linux/modules/sound.o
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and
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rmmod sound
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This may be useful if you are doing one of the following things:
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1) Debugging the sound driver
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2) Creating a new device within the sound-driver
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3) You do not the sound driver all the time (as it wastes quite a lot of
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memory for its buffers)
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Compilation:
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Go to /usr/src/linux and make the following steps:
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a) configure the sound driver: To do that call "make config" and enable the
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sound-driver -- you will be asked different questions about your
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sound-hardware (remember not to use a too big DMA-Buffer size; you
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should use 16kB, if you have 16Bit devices, otherwise you can use 32kB)
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b) disable the sound driver in the kernel: call make config again but answer
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'N' to "Sound card support"
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c) run "make modules"; the sound-driver sound.o should end up in
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/usr/src/linux/modules
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If memory is tight:
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I've allocated at about 70kB for the sound-drivers internal tables. If this
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is too much, 'insmod sound.o' will generate the following warning
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...
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use 'insmod memsize=xxxx'
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...
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You can only use this command, if you have (I think) at least
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modules-1.1.87 or up. You can also switch debugging on by running the command
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insmod sound.o debugmem=1
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Files I changed:
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I've only changed the files soundcard.c(most changes) and some changes within
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the Makefile, sound_config.h and the Makefile in /usr/src/linux/drivers
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Bugs:
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a) As the kmalloc (..., GFP_DMA) caused some unexpected errors (I don't know if
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it is my fault), I created some code, which is (by default) enabled by
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#define KMALLOC_DMA_BROKEN 1 (within soundcard.c).
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It trys to allocate a large enough region, so that the complete dma-buffer
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can be occupied in this space. If it does not fit within this region it
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doubles the size of it. But this can cause problems, if the sound-buffer is
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too big (as kmalloc can only handle regions at up to circa 100kB).
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So take care to use for 8Bit devices a sound-DMA-buffer of 32kB (maximum)
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and for 16Bit devices a maximum of 16kB. Otherwise the allocation scheme
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might fail.
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b) Buffers allocated by the different sound devices via calls to kmalloc are
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not freed, if the sound driver is removed again (these buffers tend to be
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quite small -- so it does not harm a lot)
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c) If there is not enough (kernel-) memory available, the installation of
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the sound-driver fails. (This happens quite often, if you did not install the
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driver right after booting -- [PS: I've only got 5MB of Ram, so this might
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be the source for this problem])
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Author:
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Peter Trattler (peter@sbox.tu-graz.ac.at)
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