[PATCH 00/37] fix paca memory usage and NR_CPU loops, factor ipi and simplify irq code

[Grant Likely]

On Wed, May 11, 2011 at 7:43 AM, Milton Miller <miltonm at bga.com> wrote:
[...]
> After doing a bunch of grep's on arch/sh, I think the interesting
> parts of super8 interrupt handling that Thomas referred to are in
> drivers/sh/intc.  For some reason they populate the radix tree first
> with a descriptor of their common interrupt controler abstraction
> then walk the tree, replacing the tagged elements with the pointer
> to their equivalent to irq_map.  I do not yet understand the purpose
> of this two phase allocation.

BTW, you can also write a patch now that eliminates irq_map entirely.
I just talked to tglx today and we agree in principle to move the
hwirq value and irq_domain pointer directly into irq_data (and hence
directly accessible from the irq_desc).  The final form of irq_domain
is still up in the air, but you could do an initial patch that leaves
it as platform defined, and it can be followed up with a patch series
that creates a common irq_domain definition.

g.