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Date: Fri, 28 Feb 2003 20:27:21 +0300
From: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
To: "Dmitry A. Fedorov" <D.A.Fedorov@inp.nsk.su>, linux-kernel@vger.kernel.org
Subject: Re: Proposal: Eliminate GFP_DMA
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On Fri, Feb 28, 2003 at 04:05:50PM +0000, Russell King wrote:
> Umm, question - I've seen ISA bridges with the ability to perform 32-bit
> DMA using the ISA DMA controllers.  AFAIK, Linux doesn't make use of this
> feature, except on ARM PCI systems with ISA bridges.

Alpha uses this from day 1, BTW.
Also, in 2.5 we have "isa_bridge" stuff which was intended exactly for
that - it's a pointer to pci device (real ISA bridge with appropriate
dma_mask) that can be used by non-busmastering ISA devices as a pci_dev *
arg to pci_* mapping functions.

>  Is there a reason
> why this isn't used on x86 hardware?

Given a huge number of various ISA bridges found in x86 systems,
I don't see a generic way to determine which ones can do 32-bit DMA...
Maybe kind of white list?

Ivan.
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