gpiolib: provide gpio_device_to_device()

There are users in the kernel who need to retrieve the address of the
struct device backing the GPIO device. Currently they needlessly poke in
the internals of GPIOLIB. Add a dedicated getter function.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Peter Rosin <peda@axentia.se>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>

Author: Bartosz Golaszewski

drivers/gpio/gpiolib.c

@@ -1189,6 +1189,23 @@ void gpio_device_put(struct gpio_device *gdev)
 }
 EXPORT_SYMBOL_GPL(gpio_device_put);
 
+/**
+ * gpio_device_to_device() - Retrieve the address of the underlying struct
+ *                           device.
+ * @gdev: GPIO device for which to return the address.
+ *
+ * This does not increase the reference count of the GPIO device nor the
+ * underlying struct device.
+ *
+ * Returns:
+ * Address of struct device backing this GPIO device.
+ */
+struct device *gpio_device_to_device(struct gpio_device *gdev)
+{
+	return &gdev->dev;
+}
+EXPORT_SYMBOL_GPL(gpio_device_to_device);
+
 #ifdef CONFIG_GPIOLIB_IRQCHIP
 
 /*

include/linux/gpio/driver.h

@@ -619,6 +619,8 @@ void gpio_device_put(struct gpio_device *gdev);
 DEFINE_FREE(gpio_device_put, struct gpio_device *,
 	    if (IS_ERR_OR_NULL(_T)) gpio_device_put(_T));
 
+struct device *gpio_device_to_device(struct gpio_device *gdev);
+
 bool gpiochip_line_is_irq(struct gpio_chip *gc, unsigned int offset);
 int gpiochip_reqres_irq(struct gpio_chip *gc, unsigned int offset);
 void gpiochip_relres_irq(struct gpio_chip *gc, unsigned int offset);