Re: [Kernel-discuss] RFC - platform device, IRQs and SoC devices

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Sat, Nov 25, 2006 at 11:37:50AM +0000, Ian Molton wrote:
> Ian Molton wrote:
> >Hi there.
> >
> >Im working on some SoC type devices attached to the system bus of my ARM 
> >devboard in an isa-like way.
> >
> >The devices are small SoC (System On Chip) types, with one IRQ routed to 
> >the half dozen (sub)devices on board the SoC.
> 
> I just thought of a 'third way'.
> 
> let IRQchips have their own struct irq_desc and have subdevice IRQs 
> start from 0.
> 
> since those IRQs can only be raised by the parent chip I think this 
> ought to work, and would eliminated the problem of a fixed size irq array...

It's quite possible to have:

IRQ	chip
0	irqchip_0
1	irqchip_0
2	irqchip_1
3	irqchip_0
4	irqchip_0
5	irqchip_1
6	irqchip_2
7	irqchip_2
8	irqchip_2
9	irqchip_1

Where do you start '0' for each irqchip?  How do you split the irq_desc
array between the irqchips?

(and yes there are platforms merged which do this.)

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of: