linux-kernel - [PATCH 1/2] gpio: provide gpiod_is

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Message-Id: <20250407-gpiod-is-equal-v1-1-7d85f568ae6e@linaro.org>
Date: Mon, 07 Apr 2025 09:08:14 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>, 
 Bartosz Golaszewski <brgl@...ev.pl>, Liam Girdwood <lgirdwood@...il.com>, 
 Mark Brown <broonie@...nel.org>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH 1/2] gpio: provide gpiod_is_equal()

From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

There are users in the kernel that directly compare raw GPIO descriptor
pointers in order to determine whether they refer to the same physical
GPIO pin. This accidentally works like this but is not guaranteed by any
API contract. Let's provide a comparator function that hides the actual
logic.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
 drivers/gpio/gpiolib.c        | 14 ++++++++++++++
 include/linux/gpio/consumer.h |  9 +++++++++
 2 files changed, 23 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index b8197502a5ac..2e5b6982e76d 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -265,6 +265,20 @@ struct gpio_device *gpiod_to_gpio_device(struct gpio_desc *desc)
 }
 EXPORT_SYMBOL_GPL(gpiod_to_gpio_device);
 
+/**
+ * gpiod_is_equal() - Check if two GPIO descriptors refer to the same pin.
+ * @desc: Descriptor to compare.
+ * @other: The second descriptor to compare against.
+ *
+ * Returns:
+ * True if the descriptors refer to the same physical pin. False otherwise.
+ */
+bool gpiod_is_equal(struct gpio_desc *desc, struct gpio_desc *other)
+{
+	return desc == other;
+}
+EXPORT_SYMBOL_GPL(gpiod_is_equal);
+
 /**
  * gpio_device_get_base() - Get the base GPIO number allocated by this device
  * @gdev: GPIO device
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index 45b651c05b9c..7355abadaef4 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -180,6 +180,8 @@ struct gpio_desc *devm_fwnode_gpiod_get_index(struct device *dev,
 					      enum gpiod_flags flags,
 					      const char *label);
 
+bool gpiod_is_equal(struct gpio_desc *desc, struct gpio_desc *other);
+
 #else /* CONFIG_GPIOLIB */
 
 #include <linux/bug.h>
@@ -547,6 +549,13 @@ struct gpio_desc *devm_fwnode_gpiod_get_index(struct device *dev,
 	return ERR_PTR(-ENOSYS);
 }
 
+static inline bool
+gpiod_is_equal(struct gpio_desc *desc, struct gpio_desc *other)
+{
+	WARN_ON(desc || other);
+	return false;
+}
+
 #endif /* CONFIG_GPIOLIB */
 
 #if IS_ENABLED(CONFIG_GPIOLIB) && IS_ENABLED(CONFIG_HTE)

-- 
2.45.2