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

> 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 <mj@ucw.cz> http://atrey.karlin.mff.cuni.cz/~mj/
Faculty of Math and Physics, Charles University, Prague, Czech Rep., Earth
"You can't do that in horizontal mode!"

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