On Thu, 2012-01-26 at 14:33 -0700, Grant Likely wrote:

I've got the x86 fix in my tree now.  It will be part of the next
merge.  MIPS, Microblaze and OpenRISC cannot turn on CONFIG_IRQ_DOMAIN
without rework.  I just hacked together the microblaze version, but
Michal will have to verify that it is correct.  I just posted it.  It
will be similar for the other two.

The real problem is sparc which does something entirely different for
irqs.  Rather than resolving irqs on-demand, it calculates the Linux
irq numbers at boot time for every node in the tree.  The irq_domains
will need to be set up for all interrupt controllers before sparc
begins it's big walk of the tree to resolve interrupts.  I haven't dug
into everything that needs to be done to support this.

I don't think you can count on turning on IRQ_DOMAIN on all
architectures just yet.  Adding irq_domain support directly to
irq_generic_chip is going to be difficult for that reason.  However,
it would be useful to have an irq_domain+irq_generic_chip wrapper that
can be enabled only when IRQ_DOMAIN is enabled.

Beware also that there are plenty of cases where 1 irq domain != 1 irq
chip, for example on cell or xics where a single domain can encompass
multiple chips. I don't know whether x86 APICs are the same, they could
be tho :-)

Cheers,
Ben.