Regarding hw irq to Linux irq mapping on ARM

[Benjamin Herrenschmidt]

On Wed, 2010-09-22 at 00:08 -0300, Grant Likely wrote:
> > Add all the I2C, SPI based irq extenders to that list. They seem to
> > pop up all over the place in rapid speed even in x86. We are happy
> > citizens of the embedded horror^Wuniverse now.
> 
> *shudder*
> 
> What's the irq handling latency on those?  Glad I haven't had to deal
> with any of them yet.

And i2c in many cases want to be called from sleep'able context... might
be a good idea to restrict some of these to threaded interrupts. A whole
different discussion I suppose.

Cheers,
Ben.