Re: [PATCH] x86/sfi: fix ioapic gsi range

From: Eric W. Biederman
Date: Tue Jun 08 2010 - 16:04:28 EST

"H. Peter Anvin" <hpa@xxxxxxxxx> writes:

> On 06/08/2010 01:10 AM, Alan Cox wrote:
>>>> You may not use a 1-1 mapping if you don't have legacy irqs. Linux
>>>> irqs 0-15 are the ISA irqs you may not use those irq numbers for
>> Linux IRQ 0 is "no IRQ assigned", except buried in certain bits of arch
>> specific historical knowledge.
>> Also calling 1-15 ISA IRQ lines is also somewhat misleading given they
>> are almost certainly routing for PCI devices. "PIC IRQ routing" maybe -
>> but even that is not really true on a lot of PC hardware today except by
>> convention.
> Yes, but I gather IRQ/GSI 0 is an early-acquire primary timer on MRST on
> Moorestown just as on PC/AT... just a different one. Hence "special" in
> the same sort of way. I don't really care, personally, though.

Right. I have to admit I was stunned when I realized that request_irq
works and has worked for a long time with irq 0. I think that might
actually be a bug. setup_irq is traditionally used for irq 0.

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