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