Re: [PATCH 4/5] Centralise NO_IRQ definition

From: Matthew Wilcox
Date: Tue Nov 22 2005 - 09:05:07 EST

On Tue, Nov 22, 2005 at 02:15:39PM +0000, Alan Cox wrote:
> On Maw, 2005-11-22 at 11:13 +0000, David Woodhouse wrote:
> > Yes, there are drivers which are currently broken and assume irq 0 is
> > 'no irq'. They are broken. Let's just fix them and not continue the
> > brain-damage.
> 0 in the Linux kernel has always meant 'no IRQ' and it makes it natural
> to express in C (and on some cpus more efficient too).
> What if my hardware has an IRQ -1 ;)

Then it falls off the bottom of the irq_desc array. Already tried that,
hence patch 1/5.

That was a great one to debug, btw. "The machine hangs when I select
processor type PA8000 but works with processor type PA7200". Why?
synchronize_irq() spins waiting for a bit to become clear ... for some
reason that bit was always set with PA8000 and always clear with PA7200.
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