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Date: Tue, 15 Jan 2002 17:35:51 +0100
From: Stephan von Krawczynski <skraw@ithnet.com>
To: Gerd Knorr <kraxel@bytesex.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Memory problem with bttv driver
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On Tue, 15 Jan 2002 16:16:53 +0100
Gerd Knorr <kraxel@bytesex.org> wrote:

> On Tue, Jan 15, 2002 at 02:46:52PM +0100, Stephan von Krawczynski wrote:
> > On Tue, 15 Jan 2002 14:20:17 +0100
> > Gerd Knorr <kraxel@bytesex.org> wrote:
> > 
> > > Yes.  Instead of remapping vmalloced kernel memory it gives you shared
> > > anonymous pages, then does zerocopy DMA using kiobufs.  You may run in
> > > trouble with >4GB machines.
> > 
> > Interesting.
> > What's the problem on > 4GB ?
> 
> The bt878/848 is a 32bit PCI device, it simply can't go DMA to main
> memory above 4GB.  At least on ia32, on architecures with a iommu
> (sparc, ...) it should work without trouble.

Sorry, maybe I should have clarified: what is the problem with allocating those
pages below 4GB in a >4GB box?

Regards,
Stephan

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