Re: pre 2.1.92-1 swap, and sound driver issue

David Woodhouse (Dave@imladris.demon.co.uk)
Wed, 01 Apr 1998 00:58:25 +0200


andrewtv@usa.net said:
> I'm trying to write a digital audio driver module for my Turtle Beach
> Multisound Pinnacle to work with OSS/Free which does not support it,
> however I'm running to a problem. OSS/Free seems designed to
> _require_ an audio device to be using DMA (see drivers/sound/
> audio.c:79 for instance).

> Now, this particular card does not use DMA; it uses a shared memory
> with a Motorola 56002 DSP. Are there any known plans to give OSS/Free
> the ability to use audio devices that use the sound_install_audiodrv
> call which do not use a DMA channel, but say a custom method of data
> transfer?

I came across this problem when porting the PC Speaker driver to be a modular
OSS/Free driver, rather than a standalone driver with its own major no.

The way I got round it was to fake it - make your driver pretend to use DMA
channel # -2, and hack the DMAbuf routines so they don't try to deal with the
hardware for DMA#-2, and then fake the trigger routine to copy it where you
want or point the card at it.

It's not too difficult, as long as you don't mind getting your hands dirty.
I'd release my code, but it didn't get past the proof-of-concept stage before I
had to get on with more important things. It works, but it wants rewriting
anyway.

---- ---- ----
David Woodhouse, Robinson College, CB3 9AN, England. (+44) 0976 658355
Dave@imladris.demon.co.uk http://www.imladris.demon.co.uk
finger pgp@dwmw2.robinson.cam.ac.uk for PGP key.

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