> 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!"- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/