gpio: don't compare raw GPIO descriptor pointers

Merge series from Bartosz Golaszewski <[e-mail]>:

Handling of shared GPIOs in the kernel needs some improvements. Let's
start with a simple change of not comparing GPIO descriptor pointers
directly as there's nothing that guarantees that the same physical pin
will always be represented by a single GPIO descriptor obtained by
calling gpiod_get().

drivers/gpio/gpiolib.c

···
 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
  *

drivers/regulator/core.c

···
 	mutex_lock(&regulator_list_mutex);
 
 	list_for_each_entry(pin, &regulator_ena_gpio_list, list) {
-		if (pin->gpiod == gpiod) {
+		if (gpiod_is_equal(pin->gpiod, gpiod)) {
 			rdev_dbg(rdev, "GPIO is already used\n");
 			goto update_ena_gpio_to_rdev;
 		}

include/linux/gpio/consumer.h

···
 					      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>
···
 					      const char *label)
 {
 	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 */