gpio: provide gpiod_is_equal()

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.

Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20250407-gpiod-is-equal-v1-1-7d85f568ae6e@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index b8197502a5ac598ce3c88c1e9a1d6c0b74516aac..2e5b6982e76d08f0c06ce1474a51d1c6c99e2215 100644 (file)
--- 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 45b651c05b9c87f577862bfa6cc8d627366a7712..7355abadaef460d5ed79e79f4569224a3ef41f93 100644 (file)
--- 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)