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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Sun, 4 Sep 2016 19:45:03 +0200
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To: Linus Torvalds <torvalds@linux-foundation.org>
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Hi Linus,

On Fri, Sep 2, 2016 at 7:25 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Fri, Sep 2, 2016 at 3:46 AM, Vinod Koul <vinod.koul@intel.com> wrote:
>>
>> Arm seems to define NO_IRQ. This is not available in other arch and one
>> driver (moxart-dma) is using it. I don't see why this should be arm specific.
>
> NO_IRQ is broken. We long long since agreed that 0 is "no irq", and
> that the right way to test for it is just
>
>    if (!irq) ...
>
> which is what all the generic drivers use.

[...]

> Some people have said "..but but but I have a real irq that has the
> value 0", but that's irrelevant - the kernel "irq" value isn't
> necessarily the same as the value that an interrupt _controller_ sees,
> since the interrupt controller can be hiding behind various other
> nested controllers etc. So an architecture might need to translate
> "irq" into the actual hw interrupt controller value.

Let's bite ;-)

What about the legacy timer interrupt?

$ git grep 'setup_irq(0,'
arch/alpha/kernel/sys_ruffian.c:        setup_irq(0, &timer_irqaction);
arch/avr32/kernel/time.c:       ret = setup_irq(0, &timer_irqaction);
arch/mips/kernel/i8253.c:       setup_irq(0, &irq0);
arch/x86/kernel/time.c: setup_irq(0, &irq0);
$

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds