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

[Ingo Molnar <mingo@elte.hu>]

* 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