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    SubjectRe: cat /proc/pci and NCR 810 SCSI parity error

    > I'm not sure about what the PCI spec says about side effects. Having read
    > side effect for something called a configuration space looks weird but
    > would perhaps be acceptable.

    I don't have the PCI specs at hand now, but as far as I remember, side
    effects on configuration space reads are explicitly forbidden.

    > However the worst case is that some chips manage to lockup the whole PCI
    > bus (and hence the system) when reading from some configuration registers.
    > This is a clear violation of the PCI spec and a very serious one.

    And let's point our fingers at the culprit: it's Intel. *Again* (PIIX4 ACPI).

    > Yes, but this type of things is unlikely to require frequent accesses to
    > configuration space registers. This space is designed to be essentially
    > safe to access, although maybe slow and I personnally hate side effects in
    > this area. I prefer to be able to type lspci -xx when looking for PCI
    > problems or debugging a driver (although in the last case I rather use
    > lspci -xx -s device).

    I completely agree. /proc/bus/pci restricts non-root accesses to the
    standard header (i.e., 64 bytes or 128 for CardBus bridges). Root can
    read/write everything and there is no reason for disabling this capability --
    /proc/ioports is a clean precedent for root crashing the system by just reading
    a file.

    Have a nice fortnight
    Martin `MJ' Mares <>
    Faculty of Math and Physics, Charles University, Prague, Czech Rep., Earth
    "You can't do that in horizontal mode!"

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