Subject: Re: FreeBSD Bus DMA (was Re: AdvanSys board support)
To: Noriyuki Soda <>
From: Jason Thorpe <>
List: tech-kern
Date: 06/11/1998 15:52:04
On Fri, 12 Jun 1998 06:08:39 +0900 (JST) 
 Noriyuki Soda <> wrote:

 > About bus_dmamap_callback_t, I think that reducing bounce memory size 
 > is certainly good thing. But it is pain if we must use callback in all 
 > cases.  (Think about hardware_scb in ahc driver.)
 > I think NetBSD's interface is more convenient than FreeBSD's.
 > Isn't there other way to reduce bounce memory ?

Yes, lots of ways.  But you don't have to change the interface to
bus_dma to do it.  The bounce buffer size issue is largely an issue
of the implementation that drivers never see.  To be quite honest,
I implemented it the way I did because bounce buffers were SORELY
needed, and didn't have the time to implement them differently underneath.

I've actually improved the implementation of bounce buffers a little since
the original implementation.

Jason R. Thorpe                             
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