gpio: use container_of to resolve cs5535_gpio_chip from gpio_chip

Use container_of instead of casting first structure member.
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-cs5535.c

@@ -201,7 +201,8 @@ EXPORT_SYMBOL_GPL(cs5535_gpio_setup_event);
 
 static int chip_gpio_request(struct gpio_chip *c, unsigned offset)
 {
-	struct cs5535_gpio_chip *chip = (struct cs5535_gpio_chip *) c;
+	struct cs5535_gpio_chip *chip =
+		container_of(c, struct cs5535_gpio_chip, chip);
 	unsigned long flags;
 
 	spin_lock_irqsave(&chip->lock, flags);
@@ -241,7 +242,8 @@ static void chip_gpio_set(struct gpio_chip *chip, unsigned offset, int val)
 
 static int chip_direction_input(struct gpio_chip *c, unsigned offset)
 {
-	struct cs5535_gpio_chip *chip = (struct cs5535_gpio_chip *) c;
+	struct cs5535_gpio_chip *chip =
+		container_of(c, struct cs5535_gpio_chip, chip);
 	unsigned long flags;
 
 	spin_lock_irqsave(&chip->lock, flags);
@@ -254,7 +256,8 @@ static int chip_direction_input(struct gpio_chip *c, unsigned offset)
 
 static int chip_direction_output(struct gpio_chip *c, unsigned offset, int val)
 {
-	struct cs5535_gpio_chip *chip = (struct cs5535_gpio_chip *) c;
+	struct cs5535_gpio_chip *chip =
+		container_of(c, struct cs5535_gpio_chip, chip);
 	unsigned long flags;
 
 	spin_lock_irqsave(&chip->lock, flags);