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    SubjectRe: [PATCH] x86/sfi: fix ioapic gsi range
    > The issue is what acpi calls bus 0 irqs, and how drivers deal with
    > them. We wind up having well know irqs: irqs 3 and 4 for serial
    > ports, irq 7 for parallel ports. irqs 14, and 15 for ide.

    Only we don't.

    IRQ 3/4 for serial is not true on many boxes today that have serial -
    in fact its been iffy since about the Thinkpad 600 !
    IRQ 7 for parallel is rarely used (and in fact we usually poll)
    IRQ 14/15 is wrong for ATA today as its AHCI based on modern boxes

    And all the drivers you list are *cross platform* already.

    > A bunch of these hardware devices we can get if someone connects up a
    > lpc superio chip.

    To an x86 PC class system using some very traditional (and no longer
    valid) bits of behaviour.

    > Even if sfi is never implemented on a platform where that kind of
    > hardware exists, the current sfi code is setup to coexist
    > simultaneously in the kernel with all of the infrastructure of other
    > platforms where those kinds of devices exist. Which means there can
    > be drivers compiled into your kernel that make assumptions about
    > special properties of the irqs 0-15.

    That would be a driver bug. It would be bite other systems beyond the
    legacy PC. In the PC world its been unsafe since PnP BIOS let alone
    ACPI.

    > With the current code you should get all of the remapping of the
    > gsi's out of the legacy irq space without needing to lift a finger,
    > and if someone later decides we need an irq override so we can have
    > an isa irq present on a weird embedded system on a chip the code will
    > be able to handle that easily.

    There is only one reason to care about this - that is ISA bus devices
    with software IRQ steering registers for the ISA lines. Now that might
    just about be a real reason, but as former maintainer of both serial
    and IDE (and part time fixer of parport) I'd say the other reasons are
    bunkum.

    Alan
    --


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