Re: [RFT][PATCH] generic device DMA implementation

David Mosberger (davidm@napali.hpl.hp.com)
Tue, 17 Dec 2002 19:13:45 -0800


James> The attached should represent close to final form for the
James> generic DMA API. It includes documentation (surprise!) and
James> and implementation in terms of the pci_ API for every arch
James> (apart from parisc, which will be submitted later).

James> I've folded in the feedback from the previous thread.
James> Hopefully, this should be ready for inclusion. If people
James> could test it on x86 and other architectures, I'd be
James> grateful.

James> comments and feedback from testing welcome.

Would you mind doing a s/consistent/coherent/g? This has been
misnamed in the PCI DMA interface all along, but I didn't think it's
worth breaking drivers because of it. But since this is a new
interface, there is no such issue.

(Consistency says something about memory access ordering, coherency
only talks about there not being multiple values for a given memory
location. On DMA-coherent platforms with weakly-ordered memory
systems, the returned memory really is only coherent, not consistent,
i.e., you have to use memory barriers if you want to enforce
ordering.)

Thanks,

--david
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