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SubjectRe: [RFC patch 2/3] genirq: Add buslock support for irq chips on slow busses

* Mark Brown <broonie@opensource.wolfsonmicro.com> wrote:

> On Fri, Aug 14, 2009 at 12:20:49PM +0200, Thomas Gleixner wrote:
> > On Fri, 14 Aug 2009, Pavel Machek wrote:
>
> > > AFAICT this means that driver would need to know what kind of IRQ it
> > > is hooked to, right? That will lead to some ugly code in drivers that
> > > can handle both normal and slowbus irqs, right?
>
> > Are there such drivers in reality ?
>
> Yes. The GPIO based stuff is the prime example but there's other
> examples - one is the WM831x touchscreen (no driver in mainline
> yet) which can use interrupts via the main interrupt controller on
> the CPU but also has the option of bringing the interrupt signals
> out to dedicated pins on the chip for direct connection to the CPU
> precisely to avoid the overheads of these slow interrupt
> controllers.

This would call for Thomas's first version of the patch, that is
transparent to drivers - the IRQ subsystem will know how to lock
access to the line.

How about implementing that first patch in a cleaner way - can we
somehow express the slow-bus property purely via the irqchip? Or is
that too lowlevel?

Ingo


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