[PATCH RFC 1/2] gpiolib: of: Introduce hook for missing gpio-ranges

[Bartosz Golaszewski]

On Wed, Mar 9, 2022 at 8:44 PM Stefan Wahren <stefan.wahren at i2se.com> wrote:
>
> Since commit 2ab73c6d8323 ("gpio: Support GPIO controllers without pin-ranges")
> the device tree nodes of GPIO controller need the gpio-ranges property to
> handle gpio-hogs. Unfortunately it's impossible to guarantee that every new
> kernel is shipped with an updated device tree binary.
>
> In order to provide backward compatibility with those older DTB, we need a
> callback within of_gpiochip_add_pin_range() so the relevant platform driver
> can handle this case.
>
> Signed-off-by: Stefan Wahren <stefan.wahren at i2se.com>
> ---
>  drivers/gpio/gpiolib-of.c   |  5 +++++
>  include/linux/gpio/driver.h | 12 ++++++++++++
>  2 files changed, 17 insertions(+)
>
> diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
> index 91dcf2c..45b6edb 100644
> --- a/drivers/gpio/gpiolib-of.c
> +++ b/drivers/gpio/gpiolib-of.c
> @@ -933,6 +933,11 @@ static int of_gpiochip_add_pin_range(struct gpio_chip *chip)
>         if (!np)
>                 return 0;
>
> +       if (!of_property_read_bool(np, "gpio-ranges") &&
> +           chip->of_gpio_ranges_fallback) {
> +               return chip->of_gpio_ranges_fallback(chip, np);
> +       }
> +
>         group_names = of_find_property(np, group_names_propname, NULL);
>
>         for (;; index++) {
> diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
> index b0728c8..47a5ea0 100644
> --- a/include/linux/gpio/driver.h
> +++ b/include/linux/gpio/driver.h
> @@ -489,6 +489,18 @@ struct gpio_chip {
>          */
>         int (*of_xlate)(struct gpio_chip *gc,
>                         const struct of_phandle_args *gpiospec, u32 *flags);
> +
> +       /**
> +        * @of_gpio_ranges_fallback
> +        *
> +        * Optional hook for the case that no gpio-ranges property is defined
> +        * within the device tree node "np" (usually DT before introduction
> +        * of gpio-ranges). So this callback is helpful to provide the
> +        * necessary backward compatibility for the pin ranges.
> +        */
> +       int (*of_gpio_ranges_fallback)(struct gpio_chip *gc,
> +                                      struct device_node *np);
> +
>  #endif /* CONFIG_OF_GPIO */
>  };
>
> --
> 2.7.4
>

Acked-by: Bartosz Golaszewski <brgl at bgdev.pl>