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

From: Bartosz Golaszewski <brgl@bgdev.pl>
To: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Linus Walleij <linus.walleij@linaro.org>,
	Florian Fainelli <f.fainelli@gmail.com>,
	 Nicolas Saenz Julienne <nsaenz@kernel.org>,
	Ray Jui <rjui@broadcom.com>,
	 Scott Branden <sbranden@broadcom.com>,
	 bcm-kernel-feedback-list <bcm-kernel-feedback-list@broadcom.com>,
	Arnd Bergmann <arnd@arndb.de>, Phil Elwell <phil@raspberrypi.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	 "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>
Subject: Re: [PATCH RFC 1/2] gpiolib: of: Introduce hook for missing gpio-ranges
Date: Tue, 15 Mar 2022 16:17:26 +0100	[thread overview]
Message-ID: <CAMRc=MeenhStqP0t8tSGcmhcjbHX8c3jUPTKQPS7jTzKta+vEw@mail.gmail.com> (raw)
In-Reply-To: <1646855026-9132-2-git-send-email-stefan.wahren@i2se.com>

On Wed, Mar 9, 2022 at 8:44 PM Stefan Wahren <stefan.wahren@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@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@bgdev.pl>

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