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

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Date:   Sat,  9 Apr 2022 11:51:28 +0200
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>
Cc:     bcm-kernel-feedback-list@...adcom.com,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Phil Elwell <phil@...pberrypi.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        Stefan Wahren <stefan.wahren@...e.com>
Subject: [PATCH 1/2] gpiolib: of: Introduce hook for missing gpio-ranges

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.

Fixes: 2ab73c6d8323 ("gpio: Support GPIO controllers without pin-ranges")
Signed-off-by: Stefan Wahren <stefan.wahren@...e.com>
Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
Tested-by: Florian Fainelli <f.fainelli@...il.com>
Acked-by: Bartosz Golaszewski <brgl@...ev.pl>
---
 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 ae1ce319cd78..d9b235c88b54 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -931,6 +931,11 @@ 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 98c93510640e..b5d53decea5a 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -492,6 +492,18 @@ 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 */
 };
 
-- 
2.25.1