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    SubjectRe: PCI DMA to small buffers on cache-incoherent arch
    On Mon, Jun 10, 2002 at 07:22:26PM +0200, Oliver Neukum wrote:
    >
    > > > So is the consensus now that in general drivers should make sure any
    > > > buffers passed to pci_map/unmap are aligned to SMP_CACHE_BYTES (and a
    > > > multiple of SMP_CACHE_BYTES in size)? In other words if a driver uses
    > > > an unaligned buffer it should be fixed unless we can prove (and
    > > > document in a comment :) that it won't cause problems on an arch
    > > > without cache coherency and with a writeback cache.
    > >
    > > And how about we don't call it SMP_CACHE_BYTES too? The processors
    > > where this matters certainly aren't doing SMP...
    >
    > Definitely we should call it something different so we can limit it to
    > architectures that need it.

    No. We should just make it come out to a nop for arches that don't need
    it. Otherwise we'll end up with ugly things like:
    #ifdef CONFIG_NOT_CACHE_COHERENT
    ...
    #else
    ...
    #endif

    All over things like USB...

    --
    Tom Rini (TR1265)
    http://gate.crashing.org/~trini/
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