Re: [RFC] killing the NR_IRQS arrays.

From: Eric W. Biederman
Date: Sat Feb 17 2007 - 04:08:33 EST

Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> writes:

> In addition, if we remove the numbers, archs will need basically the
> exact same services provided by the powerpc irq core for reverse mapping
> (going from a HW irq number on a given PIC back to an irq_desc *).

Ben you seem to be under misapprehension that except for the case of
ISA (0-16) the linux IRQ number is a hardware number. It is an arbitrary
software enumeration, and I think it has been that way a very long time.

> Either using a linear array for simple PICs or a radix tree for
> platforms with very big interrupt numbers (BTW. I think we have lockless
> radix trees nowadays, I can remove the spinlocks to protect it in the
> powerpc remapper).

I can only tell you that my impression of this last is that all the
world's not a PPC.

I have a version of the x86 code with a partial conversion done and
I didn't need a reverse mapping. What you call the hardware interrupt
number never happens to be interesting to me after the system is setup.

I do suspect there may be an interesting chunk of your ppc work that
probably makes sense as a library so other arches could use it.

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