Re: [V9 PATCH 2/2] irqchip: gicv2m: Add supports for ARM GICv2m MSI(-X)

[Suravee Suthikulanit]

On 11/3/2014 8:10 AM, Marc Zyngier wrote:
> On 03/11/14 09:50, Marc Zyngier wrote:
>
> > > @@ -843,10 +847,14 @@ static int gic_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
> > >          unsigned int type = IRQ_TYPE_NONE;
> > >          struct of_phandle_args *irq_data = arg;
> > >
> > > -       ret = gic_irq_domain_xlate(domain, irq_data->np, irq_data->args,
> > > -                                  irq_data->args_count, &hwirq, &type);
> > > -       if (ret)
> > > -               return ret;
> > > +       if (irq_data) {
> > > +               ret = gic_irq_domain_xlate(domain, irq_data->np, irq_data->args,
> > > +                                          irq_data->args_count, &hwirq, &type);
> > > +               if (ret)
> > > +                       return ret;
> > > +       } else {
> > > +               hwirq = virq;
> > > +       }
> >
> > I'm slightly puzzled here. What's the purpose of this? The whole goal of
> > the domain hierarchy is to avoid that kind of thing. Also, you should
> > never have to call xlate on an MSI, because it should never be described
> > in the device tree the first place.
>
> Thinking of it some more:
>
> The actual reason why this is required is because the MSI domain calls
> into this via irq_domain_alloc_irqs_parent(). But because MSIs are not
> described in DT, they do not have a of_phandle to pass down to the xlate
> helper. In this case, the v2m widget has the knowledge of what are the
> valid SPI numbers, and the core GIC code must blindly accept it.
>
> This definitely requires a fat comment, because this is far from obvious.
>
> Thanks,
>
> 	M.

I'll put in proper comments here.

Suravee

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