Re: [PATCH v2 1/4] genirq: Walk the irq_data hierarchy when resending an interrupt

Marc Zyngier
2020-09-05T09:26:47Z

Hi Valentin,

On Fri, 04 Sep 2020 20:28:38 +0100,
Valentin Schneider <valentin.schneider@arm.com> wrote:
>
>
> Hi Marc,
>
> On 03/09/20 19:32, Marc Zyngier wrote:
> > On resending an interrupt, we only check the topmost irqchip for
> > a irq_retrigger callback. However, this callback could be implemented
> > at a lower level. Use irq_chip_retrigger_hierarchy() in this case.
> >
>
> Rookie wording question here; re-reading this I'm questioning which way is
> up.
>
> From an irq_data hierarchy PoV, the topmost chip (i.e. last ->parent)
> should be the root irqchip. However, the irq_desc we get from irq_to_desc()
> ought to hold the irq_data for the lowermost irqchip in that irq_data
> hierarchy.
>
> Is it that here by "topmost" you instead mean topmost of the irqchip stack
> on top of the root (IOW furthest away from the root)?

That's indeed what I mean, but I agree that the terminology is
confusing, and often used inconsistently (by me included).

<random>
Maybe considering the irqchip stack along a vertical axis is the wrong
thing to do, and that looking at it as a volume would be marginally
better?

How about innermost (close to the CPU) vs outermost (close to the
device)?
</random>

Thanks,

M.

--
Without deviation from the norm, progress is not possible.