Michael Lorenz <macallan@netbsd.org> writes:

> Hello,
>
> On Feb 21, 2007, at 09:46, Toru Nishimura wrote:
>
>> NetBSD/arm, in general, does smart things with "ipending" global
>> variable to implement NetBSD-peculiar (other OS camp would call it
>> strange) spl(9) priority level scheme.  While this approach fits
>> with 32 way interrupt source, it is rather painful to adapt 64bit
>> source.
>
> Depends wether you really have >30 distinct interrupt sources in
> use.  Macppc for instance can have 32, 64 or 128 IRQs ( some
> powerbooks have two Heathrow PICs with 64 IRQ lines each ) but only
> a fraction is actually connected to anything. So what we do there is
> to map those interrupts actually in use into a uint32_t. Not that I
> think this is a particularly nice approach but it does the job and
> it's fairly painless.

It's not unusual on ARM embedded systems to have > 32 interrupts, as
GPIOs can be configured to generate interrupts and hardware guys love
to use GPIOs for signalling.