On Fri, 2006-09-08 at 11:25 +0100, David Howells wrote:
> Benjamin Herrenschmidt <[email protected]> wrote:
>
> > No, you do a chain handler. Look at how I do it in
> > arch/powerpc/platform/pseries/setup.c for example. It's actually
> > trivial. You install a special flow handler (which means that there is
> > very little overhead, almost none, from the toplevel irq to the chained
> > irq). You can _also_ if you want just install an IRQ handler for the
> > cascaded controller and call generic_handle_irq (rather than __do_IRQ)
> > from it, but that has more overhead. A chained handler completely
> > relaces the flow handler for the cascade, and thus, if you don't need
> > all of the nits and bits of the other flow handlers for your cascade,
> > you can speed things up by hooking at that level.
>
> Please update Documentation/DocBook/genericirq.tmpl. That doesn't mention it.
I must admit I haven't read the documentation :) I looked at the
code/patches when genirq was posted and did my powerpc implementation
based on my understanding of the code and discussions with Thomas and
Ingo. I'll have a look at the doc next week and see if I can improve it.
Cheers,
Ben.
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