Re: [PATCH 1/6] dt-bindings: mfd: add binding for Apple Mac System Management Controller

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Tue, Sep 6, 2022 at 11:31 AM Mark Kettenis <mark.kettenis@xxxxxxxxx> wrote:

> Another argument for having sub-nodes is that the firmware actually
> exposes *two* GPIO controllers.  For now we only support the "master"
> PMU GPIOs, but there also is a "slave" PMU GPIO controller that uses a
> separate set of SMC "keys".  We currently don't need any of the pins
> on the "slave", so we don't expose it in the DT yet.

That sounds backward, like we don't expose device X as DT node
because $OS doesn't use it yet. DT should just expose (by nodes or
other ways) all hardware that exist or at least all hardware we know
about no matter what $OS is using.

FWIW I think nodes makes most sense because no doubt for example
the RTC is a separate hardware unit somewhere, and so is the
GPIO. The fact that it is hidden behind a software abstraction doesn't
change the fact that the HW definitely has these discrete units.

Yours,
Linus Walleij