demuxing irqs

[Scott Wood]

On Tue, Sep 16, 2008 at 10:24:35AM -0400, Jon Smirl wrote:
> On Tue, Sep 16, 2008 at 10:14 AM, Anton Vorontsov
> <avorontsov at ru.mvista.com> wrote:
> > Assume that GPIO 8 does not translate to any IRQ, but IRQ 8 is still
> > valid virq b/c it is mapped for another IRQ controller (particularly
> > lots of kernel code assumes that IRQ 8 is 8259 PIC's CMOS interrupt,
> > the PIC and IRQ8 is widely used on PowerPC).
> 
> Set the base in the GPIO struct such that this won't happen.  You can
> set the base greater than MAX_IRQ.

And then you'll conflict with some other subsystem that decides to engage
in the same shenanigans.

Just allocate a chunk of virq space like any other cascaded IRQ
controller.

-Scott