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Date: Thu, 9 Dec 2004 20:05:29 -0800 (PST)
From: "Kamal R. Prasad" <kamalpr@yahoo.com>
To: Julian Elischer <julian@elischer.org>,
	"Kamal R. Prasad" <kamalp@acm.org>
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--- Julian Elischer <julian@elischer.org> wrote:

> 
> 
> Kamal R. Prasad wrote:
> 
> >
> > My usb device probably doesn't have a dma
> controller, so I don't think 
> > the bulk pipe can use any memory allocated by
> bus_dma. [Pl. correct me 
> > if Im wrong this].
> > thanks
> > -kamal
> >
> all USB devices use full scatter-gather DMA.  UHCI
> and OHCI are limitted 
> I believe to 4GB of ram.
> EHCI (USB2) has a 64 bit extension that allows all
> DMAs  of data to be 
> 64 bit addresses.
> I don't know however which chips support the 64 bit
> extensions.
> 
So how does one use bus_dma within the USB framework?
The API exists, but I don't think any of the src code
in src/sys/dev/usb actually uses bus_dma. Oh btw -my
data transfer is < 100K, so the 64-bit thing is not an
issue.

regards
-kamal

> 
> 
> 


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