io-domain voltages as regulators?

[heiko@sntech.de (Heiko Stübner)]

Hi Mark, Linus,

I'd like to clarify what the appropriate way to handle pin output voltages is. 
On the Rockchip SoCs the voltage for some groups of pins can be set between 
3.3V and 1.8V ... like the MMC/SD pins who need this to support UHS mode 
cards.

In [0] when talking about something different, Linus Walleij described a 
similar case as

"I think we need to have a discussion with Mark Brown on how to
handle this.
We have previously had the case of MMC/SD level-shifters, where
a certain setting gives a certain level of signals out, and another setting
gives another level. Like two discrete levels.
So we modeled that as a regulator provider inside the pin control
driver eventually, see sh-pfc/pfc-sh73a0.c"

As this sound like exactly the thing I'm trying to solve, is handling this via 
a regulator the correct general way?


Thanks
Heiko

[0] https://lkml.org/lkml/2014/5/28/147