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    SubjectVGA PCI IO port reservations

    I've been looking at a number of VGA cards recently, and I've started
    wondering out the Linux resource management as far as allocation of
    IO ports. I've come to the conclusion that it does not contain all
    information necessary to allow allocations to be made safely.

    Thus far, VGA cards that I've looked at scatter extra registers through
    out the PCI IO memory region without appearing in the PCI BARs. In fact,
    for some cards there wouldn't be enough BARs to list them all.

    For example, S3 cards typically use:

    0x0102, 0x42e8, 0x46e8, 0x4ae8, 0x8180 - 0x8200, 0x82e8, 0x86e8,
    0x8ae8, 0x8ee8, 0x92e8, 0x96e8, 0x9ae8, 0x9ee8, 0xa2e8, 0xa6e8,
    0xaae8, 0xaee8, 0xb2e8, 0xb6e8, 0xbae8, 0xbee8, 0xe2e8,
    0xff00 - 0xff44

    And Trident TGUI9440 uses:

    0x2120, 0x43c4

    Cyber2000-type cards use:

    0x0102, 0x46e8

    These aren't guaranteed to be exhaustive listings either.

    Some of these cards require writes to these registers to "wake them up"
    so I think we can assume that these cards are listening for accesses to
    those ports. If we allocate another device to use that region, we could
    well end up getting IO port clashes.

    Surely we should be reserving these regions before we start to allocate
    resources to PCI cards?

    |_____| ------------------------------------------------- ---+---+-
    | | Russell King --- ---
    | | | | / / |
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    / | THE developer of ARM Linux |+| /|\
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