Enable buttons GPIO passthrough

[Linus Walleij]

Hi Kwin!

On Tue, Jan 15, 2019 at 8:21 AM Wang, Kuiying <kuiying.wang at intel.com> wrote:

> My proposal to enable buttons GPIO pass-through based on pinmux driver as following:
> 1. remove codes about SCU7C clearance (from line 194 to line 236) in
> aspeed_sig_expr_set function in pinctrl-aspeed.c file.
> 2. create 2 new functions in pinctrl-aspeed.c file: “aspeed_gpio_passthrough_enable”
> and “aspeed_gpio_passthrough_disable”

These are coding implementation issues that you need to discuss with
the maintainer of pinctrl-aspeed.c, Andrew.

> 3. bind button gpio to pinctrl

This will just be a pin control state like "default" or any other stare.

What you need to do first is establish a standard for this, so augment the
pin control bindings and the generic parser code to handle this and
provide a new enumerator back to .set_config in the pin config
portion of the pin control driver.

So:

Step 1: standardize pin pass through for everyone
Step 2: implement support for this in the Aspeed driver

I think using a name like "gpio-passthrough" is misleading, something
describing what is actually happening, like "latch" or just "passthrough"
is better.

Yours,
Linus Walleij