Subject: Re: [machdep_calls] IRQ

From: Michael Ellerman <[email-masked]>
Date: Thu, 21 Aug 2008 18:02:47 +1000

On Thu, 2008-08-21 at 09:13 +0200, Sébastien Chrétien wrote:
> Hello,
> 
> What are the constraints in order to implement a irq_init function ? 

You mean ppc_md.init_IRQ() ?

If so, it's a hook you can use to setup your interrupt controller. It's
called from init_IRQ() (arch/powerpc/kernel/irq.c), which is called from
start_kernel() (init/main.c).

Not long after it is called irqs are enabled. I think it is the last
callback into arch code before irqs are enabled.

When it is called the device tree is unflattened, so you can use the of_
API. Bootmem is setup so you can use alloc_bootmem(), but you can't
kmalloc yet. ioremap should work.

> What is the aim or get_irq ? Does it retun an information about the
> mask, the states, or... ?

The aim of ppc_md.get_irq() ? It's called from do_IRQ()
(arch/powerpc/kernel/irq.c) which is called from assembler in the
appropriate head_x.S

It just returns the number (virtual number) of the irq that just fired.
If for some reason you took a spurious interrupt it should return
NO_IRQ.

I'm not sure what you mean about masks or states, someone else might
though.

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person