Re: [PATCH 00/16] dyn_array and nr_irqs support v2

From: Eric W. Biederman
Date: Fri Aug 01 2008 - 22:43:22 EST


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

> I also see little value in stably encoding IRQ numbers using geographical
> identifiers. It seems that the only case where you care that an interrupt
> number is stable is when it is *not* tied to a geographically addressed entity,
> so why does it matter?

In the case of msi it is a minor. In the case of GSIs from ACPI it dramatically
simplified the code, and improved it's reliability. Because then everyone including
ACPI was always using the same.

So in general principle I think we should have stable irq numbers if we can. Which
allows someone to say I have a problem with irq X. And it will always be irq X on
their box. An extra level of indirection makes debugging more difficult.

Having a human readable name like: eth0irq22 or hbairq5 is likely just
as good in the case of msi. Still all of the users interfaces today take numbers.
So we are stuck with dealing with numbers for a long time to come.

Eric
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