> 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.
Seems to me rather _implicitely_ assumed.
> > 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).
Culprit of what?
Intel and Symbios break your preferred code by violating an implicitely
assumed PCI requirement, but your preferred code may break running
systems.
If I were in your shoes, I would not expect all users who will get their
running system broken by 'lspci' to point their fingers in the direction
you suggest. ;-)
> > 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.
Are you requiring all Linux System administrator to be as knowledgeable as
us on PCI technology? My opinion is that there is at least reason to
_clearly_ discourage users to press this _red_ _button_, unless you just
want _millions_ of fingers to point at your direction. ;-)
Regards,
Gerard.
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