Regarding hw irq to Linux irq mapping on ARM

[Mark Brown]

On Wed, Sep 22, 2010 at 11:51:11AM +0100, Mark Brown wrote:
> On Wed, Sep 22, 2010 at 12:08:17AM -0300, Grant Likely wrote:

> > What's the irq handling latency on those?  Glad I haven't had to deal
> > with any of them yet.

> Milisecondish, but depends on bus congestion and bus type.  You need to
> schedule a thread which then does one but typically more register I/O
> operations on the device (read one or more IRQ status registers, and
> typically write back to acknowledge the interrupts as well).  These tend
> for obvious reasons to be for low volume interrupts like jack detection.

Incidentally, if you want to look at an implementation the wm831x
contains an implementation of such a controller (in drivers/mfd/wm831x-irq.c)
the structure of which has been cloned for quite a few of these chips.