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    Date
    SubjectRe: [BUG] 2.6.26-rc1 broke X on SPARC Ultra5
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    From: "Dave Airlie" <airlied@gmail.com>
    Date: Wed, 4 Jun 2008 06:45:57 +1000

    > Wow thats a major userspace regression to ship, we'd never get away
    > with doing that on x86 platforms.

    x86 has how many maintainers and contributors last time you checked?

    Meanwhile X itself shipped mostly-non-working for PCI devices on sparc
    for years. And would you also not argue that it's broken to begin
    with that the older X servers cannot work properly without a root PCI
    controller being there?

    The only way I can work around this issue is to provide a virtual host
    bridge driver in the kernel, and I tried to do that, but it doesn't
    work which is why the change got installed that did.

    We'd need this because on many sparc64 machines the PCI host bridge
    (and some sub-bridges) aren't even accessible via PCI config space.

    If you provide a virtual host bridge, you have to emulate all of
    the PCI config space accesses, you have to provide the expected
    linkage and hierarchy with the rest of the PCI devices, and you
    also have to do all of the I/O and MEM space range bits correctly
    too.

    For PCI-E and sub-bridges this becomes even more complicated, and
    frankly a waste of time.

    In short you have to implement an entire non-trivial emulation layer
    for this stuff.

    I'm the only sparc64 platform developer, so my time is better spent
    moving forward and making sure that libpciaccess based X servers
    aren't so broken and do the right thing in a way which works in a
    maintainable long term manner.


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