[PATCH v4 3/5] irqchip: Add DT binding doc for the virtual irq demuxer chip

Boris Brezillon
2015-02-11T16:15:15Z

On Wed, 11 Feb 2015 15:57:20 +0000
Mark Rutland <mark.rutland@arm.com> wrote:

> [...]
>
> > > > > So for the flag at request time approach to work, all the drivers using
> > > > > the interrupt would have to flag they're safe in that context.
> > > >
> > > > Something like IRQF_"I can share the line with a timer" I guess? That wouldn't
> > > > hurt and can be checked at request time even.
> > >
> > > I guess that would have to imply IRQF_SHARED, so we'd have something
> > > like:
> > >
> > > IRQF_SHARED_SUSPEND_OK - This handler is safe to call spuriously during
> > > suspend in the case the line is shared. The
> > > handler will not access unavailable hardware
> > > or kernel infrastructure during this period.
> > >
> > > #define __IRQF_SUSPEND_SPURIOUS 0x00040000
> > > #define IRQF_SHARED_SUSPEND_OK (IRQF_SHARED | __IRQF_SUSPEND_SPURIOUS)
> >
> > What about
> >
> > #define __IRQF_TIMER_SIBLING_OK 0x00040000
> > #define IRQF_SHARED_TIMER_OK (IRQF_SHARED | __IRQF_TIMER_SIBLING_OK)
> >
> > The "suspend" part is kind of a distraction to me here, because that really
> > only is about sharing an IRQ with a timer and the "your interrupt handler
> > may be called when the device is suspended" part is just a consequence of that.
>
> My rationale was that you didn't really care who else was using the IRQ
> (e.g. the timer); you're just stating that you can survive being called
> during suspend (which is what the driver may need to check for in the
> handler if the device happens to be powered down or whatever).
>
> So I guess I see it the other way around. This is essentially claiming
> we can handle sharing with IRQF_NO_SUSPEND rather than IRQF_TIMER.
>
> > So IMO it's better to have "TIMER" in the names to avoid encouraging people to
> > abuse this for other purposes not related to timers.
>
> In the end a name is a name, and if you think IRQF_SHARED_TIMER_OK is
> better I shan't complain.
>
> The fundamental issue I'm concerned with is addressed by this approach.

Okay then, is anyone taking care of submitting such a patch (Mark ?) ?

--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering