Re: [PATCH] rtc: abx80x: Add support for autocalibration filter capacitor

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On Fri, Jun 12, 2020 at 5:48 AM Kevin P. Fleming <kevin+linux@xxxxxxx> wrote:
>
> On Wed, Jun 10, 2020 at 11:16 AM Alexandre Belloni
> <alexandre.belloni@xxxxxxxxxxx> wrote:
> > When working with RTCs, there is one issue though: boolean properties
> > are not working well because there is no way to express the 3 different
> > conditions:
> >  1/ the capacitor is present, set the register
> >  2/ the capacitor is absent, clear the register
> >  3/ the device tree didn't have this property until not and the register
> >    may have been set or cleared using another mean, don't touch it.
> >
> > As your patch is written, it only handles 1 and 3 which is probably the
> > safest option but then we will never have a way to clear it from the
> > driver. I'd say that this is not an issue but it is also something we
> > will never be able to change without breaking some setups.
>
> I agree. I could implement this as an enumerated string option which
> accepts 'yes' or 'no'. Those would cover cases 1 and 2, and the
> absence of the property would be case 3. I looked through the bindings
> that exist and didn't see any examples of properties configured this
> way, but I think it would be understandable to users.

It's a solved problem:

foo-feature = 0; //disable
foo-feature = 1; //enable
<no prop> // Leave feature configured as-is

Rob



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