On Wed, 2 Mar 2011, Will Deacon wrote:

Hi Thomas,

quoted

Can you please take the time and explain me the difference of the
following:

irqchip1.c

struct irq_chip1;

handle_primary_irq(int irq, struct irq_desc *desc)
{
	chip->irq_ack();
	desc->demux();
}

init()
{
	irq_set_chip(PRIMARY_IRQ, &irq_chip1);
	irq_set_primary_handler(PRIMARY_IRQ, handle_primary_irq);
}

I think with this approach you get the exact opposite problem; that
is the primary irq_chip doesn't know which IRQs are going to be
demuxed so it cannot know at init time which IRQs need their primary 
handler set. Is the idea that you set_primary_handler for all IRQs,
stash that in the descriptor somewhere and then replace handle_irq
with the primary handler when a demux handler is registered?

I guess I'm missing something here,

No, I missed that. Darn, yes this would need storing the
primary_handler in some separate pointer or having a callback into the
chip implementation to make this fully distangled.

Grmbl.

	tglx