[RFC PATCH 1/5] gpio: gpiolib: Add core support for maintaining GPIO values on reset

[Andrew Jeffery]

On Fri, 2017-10-20 at 09:17 +0200, Linus Walleij wrote:
> > On Fri, Oct 20, 2017 at 5:37 AM, Andrew Jeffery <andrew at aj.id.au> wrote:
> 
> > GPIO state reset tolerance is implemented in gpiolib through the
> > addition of a new pinconf parameter. With that, some renaming of helpers
> > is done to clarify the scope of the already existing
> > gpiochip_line_is_persistent(), as it's now ambiguous as to whether that
> > means on suspend, reset or both.
> 
> Isn't it most reasonable to say persistance covers both cases, reset
> and/or sleep? This seems a bit like overdefined.

I definitely had some internal debate about that. I erred on the side of
avoiding potential change in expectations for the arizona. If you consider that
overdefined then I'm happy to go the other way.

> 
> So can we say that is this flag is set, the hardware and driver should
> do its best to preserve the value across any system disruptions.
> 
> We can change the wording of course, patches welcome for that.

Yep.

> 
> But do we really need to distinguish the cases of disruption and
> whether we cover up for them or not?
> 
> I would say we can deal with that the day we have a system with
> two register bits (or similar) where you can select to preserve across
> sleep, reset, one or the other, AND there is also a usecase such that
> a user wants to preserve the value across reset but not suspend or
> vice versa.
> 
> I suspect that will not happen.

A very reasonable approach.

Cheers for the feedback.

Andrew
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