Re: mpparse.c question

From: Ingo Molnar (
Date: Fri Feb 02 2001 - 12:45:43 EST

On Fri, 2 Feb 2001, Maciej W. Rozycki wrote:

> > Can that happen, is that important?
> >
> > Silly question: Why can't we ignore all but the first pin? If we don't
> > enable the additional pins, we don't have to disable them during
> > disable_irq().
> Possibly yes -- I haven't seen such a system.

it does exist, and the feature fixed a real bug. I dont remember which
system exactly :-|

> > Btw, is is correct that the isa irq's are always connected to the first
> > io apic? find_isa_irq_pin() doesn't handle that, and the caller just
> > access io apic 0.
> It appears it happens so for all systems checked so far. The MPS does
> not seem to enforce this configuration, so we might relax this
> dependency for flexibility. Note that not only find_isa_irq_pin()
> hardcodes this assumption -- setup_ExtINT_IRQ0_pin() does as well, for
> example.

(hm, dont we have an assert in there to catch ISA IRQs bound to the second
IO-APIC?) In any case, it would be a very surprising move if anyone added
a second IO-APIC for the sake of *ISA* devices. This would be truly


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