[PATCH v3 00/25] irq_domain generalization and refinement

On Sat, 2012-02-04 at 22:17 +0000, Russell King - ARM Linux wrote:

On Fri, Jan 27, 2012 at 02:35:54PM -0700, Grant Likely wrote:

quoted

Hey everyone,

This patch series is ready for much wider consumption now.  I'd like
to get it into linux-next ASAP because there will be ARM board support
depending on it.  I'll wait a few days before I ask Stephen to pull
this in.

Grant,

Can you answer me this: does this irqdomain support require DT?

The original powerpc code this is based on didn't require it. It was an
explicit design decision and I remember insisting that Grant follows it,
but I haven't yet reviewed his last batch.

DT is orthogonal. You have "helpers" that use the DT to resolve the
domain of an interrupt source and do the mapping for you, but I made
sure that you call always still create domains and map interrupts using
explicit domain pointers & hw numbers.

(And I need them to deal with ancient broken device-tree's on some
platforms such as oldworld PowerMacs).

The question comes up because OMAP has converted some of their support
to require irq domain support for their PMICs, and it seems irq domain
support requires DT.  This seems to have made the whole of OMAP
essentially become a DT-only platform.

 .../...

Now, here's the thing: I believe that IRQ domains - at least as far as
the hwirq stuff - should be available irrespective of whether we have
the rest of the IRQ domain support code in place, so that IRQ support
code doesn't have to keep playing games to decode from the global
space to the per-controller number space.

I believe that would certainly help the current OMAP problems, where
the current lack of CONFIG_IRQ_DOMAIN basically makes the kernel oops
on boot.

How we fix this regression for 3.4 I've no idea at present, I'm trying
to work out what the real dependencies are for OMAP on this stuff.

Finally, do we need asm/irq.h in our asm/prom.h ?  That's causing
fragility between DT and non-DT builds, because people are finding
that their DT builds work without their mach/irqs.h includes but
fail when built with non-DT.  The only thing which DT might need -
at the most - is NR_IRQS, but I'd hope with things like irq domains
it doesn't actually require it.

Cheers,
Ben.