pinctrl: add function to retrieve range from pin

This adds a function to the pinctrl core to retrieve the GPIO
range associated with a certain pin for a certain controller.
This is needed when a pinctrl driver want to look up the
corresponding struct gpio_chip for a certain pin. As the
GPIO drivers can now create these ranges themselves, the
pinctrl driver no longer knows about all its associated GPIO
chips.
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/core.c

@@ -363,6 +363,30 @@ struct pinctrl_dev *pinctrl_find_and_add_gpio_range(const char *devname,
 }
 EXPORT_SYMBOL_GPL(pinctrl_find_and_add_gpio_range);
 
+/**
+ * pinctrl_find_gpio_range_from_pin() - locate the GPIO range for a pin
+ * @pctldev: the pin controller device to look in
+ * @pin: a controller-local number to find the range for
+ */
+struct pinctrl_gpio_range *
+pinctrl_find_gpio_range_from_pin(struct pinctrl_dev *pctldev,
+				 unsigned int pin)
+{
+	struct pinctrl_gpio_range *range = NULL;
+
+	/* Loop over the ranges */
+	list_for_each_entry(range, &pctldev->gpio_ranges, node) {
+		/* Check if we're in the valid range */
+		if (pin >= range->pin_base &&
+		    pin < range->pin_base + range->npins) {
+			return range;
+		}
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(pinctrl_find_gpio_range_from_pin);
+
 /**
  * pinctrl_remove_gpio_range() - remove a range of GPIOs fro a pin controller
  * @pctldev: pin controller device to remove the range from

include/linux/pinctrl/pinctrl.h

@@ -139,6 +139,9 @@ extern void pinctrl_remove_gpio_range(struct pinctrl_dev *pctldev,
 
 extern struct pinctrl_dev *pinctrl_find_and_add_gpio_range(const char *devname,
 		struct pinctrl_gpio_range *range);
+extern struct pinctrl_gpio_range *
+pinctrl_find_gpio_range_from_pin(struct pinctrl_dev *pctldev,
+				 unsigned int pin);
 
 #ifdef CONFIG_OF
 extern struct pinctrl_dev *of_pinctrl_get(struct device_node *np);