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SubjectRe: [parisc-linux] Untested port of parisc_device to generic device interface
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Miles Bader wrote:
> I can't speak for `real machines,' but on my wierd embedded board,
> pci_alloc_consistent allocates from a special area of memory (not
> located at 0) that is the only shared memory between PCI devices and the
> CPU. pci_alloc_consistent happens to fit this situation quite well, but
> I don't think a bitmask is enough to express the situation.

grundler@dsl2.external.hp.com said:
> HP PARISC V-Class do that as well. The "consistent" memory lives on
> the PCI Bus Controller - not in host mem. Note that parisc-linux does
> not (yet) support V-class.

Actually, I think dma_mask and consistent memory are orthogonal problems.
dma_masks are used by the I/O subsystem to determine whether direct DMA to a
memory region containing an I/O buffer is possible or whether it has to be
bounced. Consistent memory is usually allocated for driver specific
transfers. The I/O subsystem doesn't usually require the actual I/O buffers
to be in consistent memory.

James


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