Re: [patch 2.6.14-rc2 0/5] swiotlb maintenance and x86_64 dma_sync_single_range_for_{cpu,device}

From: Grant Grundler <iod00d_at_hp.com>
Date: 2005-09-27 08:46:03
On Mon, Sep 26, 2005 at 03:08:23PM -0700, Luck, Tony wrote:
> Historically swiotlb.c was written with just PCI in mind (hence
> all the comments ("... implement the PCI DMA API",  "The PCI address
> to use is returned", "teardown the PCI dma mapping") and a few
> error messages ("PCI-DMA: Out of SW-IOMMU space ...", "PCI-DMA: Memory
> would be corrupted", "PCI-DMA: Random memory would be DMAed").
> Perhaps back then the only options were PCI and ISA????

Yes. The DMA interface davem/et al introduce in linux-2.4 only
supported "PCI-Like" busses. Ie the API required struct pci_dev.

> Matthew is probably technically right in that this is a more
> generic interface ... but is it actually being used for anything
> other than PCI?  Will it ever be so used?

Besides 32-bit PCI devices, I expect legacy 24-bit E/ISA DMA will
need it.  Is ISA ~= PCI? I never got a clear answer on that.
I'm inclined to say it's not.

But since swiotlb complies with DMA-API interface and is not related
to any particular type of bus, I'd rather it go into lib/ instead of
drivers/pci.

hth,
grant
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Received on Tue Sep 27 08:46:36 2005

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