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    SubjectRe: [Patch v2] Make PCI extended config space (MMCONFIG) a driver opt-in
    On Sat, Jan 12, 2008 at 09:45:57AM -0800, Arjan van de Ven wrote:
    > btw this is my main objection to your patch; it intertwines the conf1
    > and mmconfig code even more.

    There is nothing wrong with it; please realize that mmconf and conf1 are
    just different cpu-side interfaces. Both produce precisely the *same* bus
    cycles as far as the lower 256-byte space is concerned.

    > When (and I'm saying "when" not "if") systems arrive that only have
    > MMCONFIG for some of the devices, we'll have to detangle this again,
    > and I'm really not looking forward to that.

    MMCONFIG for *some* of the devices? This doesn't sound realistic
    from technical point of view.
    MMCONFIG-only systems? Sure. I really hope to see these. But it won't
    be PC-AT architecture anymore. It has to be something like alpha,
    for instance, fully utilizing the 64-bit address space, and we'll have
    to have the whole low-level PCI infrastructure completely different
    for these future platforms anyway.
    Right now, each and every x86 chipset *does* require working
    conf1 just in order to set up the mmconf aperture. It's the very
    fundamental thing, sort of design philosophy.

    Ivan.


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