Subject: Re: buslogic/adaptec conflicts
To: None <Mike.Long@analog.com>
From: None <Havard.Eidnes@runit.sintef.no>
Date: 04/05/1996 18:10:21
> >Sounds cards are a good example of where `bounce buffers' are exactly
> >the wrong thing to do. It means you can't ever mmap() the sound
> Bounce-buffering is only needed by bus master cards, yes? I've
> *never* seen a bus-mastering sound card.
Hm, not exactly, especially if you are in the "hair-splitting
mood" ;-) It depends on what you call "bounce buffering": either
the variant NetBSD doesn't have at present (support for ISA
bus-master cards in machines with >16MB memory), or the more
generic function of limiting ISA DMA to the <16MB region. From
my rummaging in the NetBSD internals a while ago, I seem to
remember that there is already bounce buffer support in for the
on-board DMA controller, and as you note all the currently
supported sound cards relies on the on-board DMA controller
(i.e. they are not ISA bus-master cards).
I agree that if we are to provide mmap capability for /dev/audio,
it's probably best to avoid that bouncing as well.