Could resource_size can be used for IORESOURCE_IRQ in device tree?

[arnd@arndb.de (Arnd Bergmann)]

On Wednesday 27 June 2012, zhangfei gao wrote:
> 
> Excuse me,
> I have one question when using device tree to get resource_size for
> IORESOURCE_IRQ
> 
> Without dt,
> static struct resource
> {
>                 .start  = 18,
>                 .end    = 19,
>                 .flags  = IORESOURCE_IRQ,
> },
> iores = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
> resource_size(iores) = 2 can be used to get how many irq.
> iores->start = 18; iores->end = 19;

IMHO we should just discourage this from being done.
While the API allows you to put multiple interrupts
into a single resource, it does not generally work,
e.g. when the same device is used in another SoC that
puts connects the interrupt lines to non-contiguous
irqs.

It also breaks down with sparse IRQs when you move
away from legacy irqdomains and the linux-internal numbers
that you put in the resource are not related to the hw
numbers any more.

> Is there any API directly get resource number in dt, like resource_size(iores).
> The reason is interrupts is not constant, and we want to parse
> directly from resource.
> If only one irq, then driver parse irqs internally.
> Only if irq number same as channel number, then every channel have own irq.
> It seems inconvenient get irq number one by one and check whether they
> equals channel number or not.

Which driver is it?

I guess in any case the solution would be to split the platform IRQ resource
and change the driver to just read the IRQs individually like most other
drivers do.

	Arnd