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    SubjectRe: [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:
    > > 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.


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