Re: [PATCH 5/8] watchdog: bindings: Provide ST bindings for ST's LPC Watchdog device

Lee Jones
2014-12-18T09:04:11Z

We
On Thu, 18 Dec 2014, Arnd Bergmann wrote:

> On Thursday 18 December 2014 08:13:34 Lee Jones wrote:
> > On Wed, 17 Dec 2014, Arnd Bergmann wrote:
> >
> > > On Wednesday 17 December 2014 16:45:24 Lee Jones wrote:
> > > > +- compatible : Must be one of: "st,stih407-lpc" "st,stih416-lpc"
> > > > + "st,stih415-lpc" "st,stid127-lpc"
> > > > +- reg : LPC registers base address + size
> > > > +- interrupts : LPC interrupt line number and associated flags
> > > > +- clocks : Clock used by LPC device (See: ../clock/clock-bindings.txt)
> > > > +- st,lpc-mode : The LPC can run either one of two modes ST_LPC_MODE_RTC [0] or
> > > > + ST_LPC_MODE_WDT [1]. One (and only one) mode must be
> > > > + selected.
> > > >
> > >
> > > I'm glad you got it to work with two drivers for the same device.
> > >
> > > With this binding, I'm still a bit unhappy about the st,lpc-mode property,
> > > in particular since you rely on a shared include file for something that
> > > can only be set in one way or another and always has to be present.
> > >
> > > Why not just use a boolean property that enforces one mode when present
> > > and another mode when absent?
> >
> > There is nothing stopping me from doing that, and it was a
> > consideration. I concluded that this method would be more explicit
> > however. Both when describing our choices in DT and at a functional
> > level within each of the drivers.
> >
> > Let me know if you fundamentally disagree and I can fix-up.
>
> I generally don't like header files that define interfaces between C code
> and DT nodes. There are cases where it's the least ugly solution, but I don't
> think this is one of them.
>
> If you want to be more explicit about the modes, how about having one
> boolean property per mode? That would also allow devices that could be
> driven in either mode, e.g. if you have only one instance of this device.

Isn't this was you suggested above?

Making a decision on the absence is a property is what I'm calling
not-explicit. If it's accidentally left off the driver(s) won't issue a
warning, it'll just assume that the lack of this boolean property was
intentional and go follow the Watchdog path for instance.

But as I briefly mentioned to you elsewhere, there are actually 3
devices (Watchdog, RTC and Global Timer). How would you like to
handle that with a Boolean property when we introduce this new driver?

--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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