Re: [PATCH v3 2/2] gpio: mmio: track the direction of chips without direction registers

[Mehmet Fide <mehmet.fide@gmail.com>]

From: Mehmet Fide <mehmet.fide@screeningeagle.com>

> What about just implementing generic optional get_config()
> in struct gpio_chip, implement a likewise generic
> gpiochip_generic_get_config() in gpiolib and use that as
> the fallback?

Yes, that is cleaner: gpio-mmio then knows nothing about pinctrl, the
same way it does not for set_config today. v4 will add the callback and
gpiochip_generic_get_config() as a mirror of gpiochip_generic_config(),
with gpio-mmio installing it for the pinctrl backend and seeding the
shadow through gc->get_config.

One detail for the generic helper: with CONFIG_PINCTRL off the
pinctrl_gpio_get_config() stub returns 0 and leaves *config alone, so
the helper returns -ENOTSUPP there instead of pretending it answered,
like gpiochip_generic_config() does for a chip without pin ranges.

> I don't think it is necessary to provide any consumer API for this
> such as gpiod_get_config(gpiod); as no-one really needs it, we can
> keep it as a private thing in struct gpio_chip for now.

Agreed, nothing outside the chip needs it.

Patch 1 stays as it is, minus the npins check I already told the
Sashiko bot was redundant.

Thanks,
Mehmet