regulator: rpi-panel-attiny: use lock guards for the state mutex

Use mutex lock guards from linux/cleanup.h to simplify the driver code.

Note that ret must be initialized in order to avoid a build warning as
scoped_guard() is implemented as a for loop.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://patch.msgid.link/20250408-gpiochip-set-rv-regulator-v1-3-a18b6154b31a@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Bartosz Golaszewski

drivers/regulator/rpi-panel-attiny-regulator.c

@@ -6,6 +6,7 @@
  */
 
 #include <linux/backlight.h>
+#include <linux/cleanup.h>
 #include <linux/err.h>
 #include <linux/gpio/driver.h>
 #include <linux/i2c.h>
@@ -94,7 +95,7 @@ static int attiny_lcd_power_enable(struct regulator_dev *rdev)
 {
 	struct attiny_lcd *state = rdev_get_drvdata(rdev);
 
-	mutex_lock(&state->lock);
+	guard(mutex)(&state->lock);
 
 	/* Ensure bridge, and tp stay in reset */
 	attiny_set_port_state(state, REG_PORTC, 0);
@@ -115,16 +116,14 @@ static int attiny_lcd_power_enable(struct regulator_dev *rdev)
 
 	msleep(80);
 
-	mutex_unlock(&state->lock);
-
 	return 0;
 }
 
 static int attiny_lcd_power_disable(struct regulator_dev *rdev)
 {
 	struct attiny_lcd *state = rdev_get_drvdata(rdev);
 
-	mutex_lock(&state->lock);
+	guard(mutex)(&state->lock);
 
 	regmap_write(rdev->regmap, REG_PWM, 0);
 	usleep_range(5000, 10000);
@@ -136,28 +135,24 @@ static int attiny_lcd_power_disable(struct regulator_dev *rdev)
 	attiny_set_port_state(state, REG_PORTC, 0);
 	msleep(30);
 
-	mutex_unlock(&state->lock);
-
 	return 0;
 }
 
 static int attiny_lcd_power_is_enabled(struct regulator_dev *rdev)
 {
 	struct attiny_lcd *state = rdev_get_drvdata(rdev);
 	unsigned int data;
-	int ret, i;
-
-	mutex_lock(&state->lock);
-
-	for (i = 0; i < 10; i++) {
-		ret = regmap_read(rdev->regmap, REG_PORTC, &data);
-		if (!ret)
-			break;
-		usleep_range(10000, 12000);
+	int ret = 0, i;
+
+	scoped_guard(mutex, &state->lock) {
+		for (i = 0; i < 10; i++) {
+			ret = regmap_read(rdev->regmap, REG_PORTC, &data);
+			if (!ret)
+				break;
+			usleep_range(10000, 12000);
+		}
 	}
 
-	mutex_unlock(&state->lock);
-
 	if (ret < 0)
 		return ret;
 
@@ -190,16 +185,14 @@ static int attiny_update_status(struct backlight_device *bl)
 	int brightness = backlight_get_brightness(bl);
 	int ret, i;
 
-	mutex_lock(&state->lock);
+	guard(mutex)(&state->lock);
 
 	for (i = 0; i < 10; i++) {
 		ret = regmap_write(regmap, REG_PWM, brightness);
 		if (!ret)
 			break;
 	}
 
-	mutex_unlock(&state->lock);
-
 	return ret;
 }
 
@@ -217,7 +210,7 @@ static void attiny_gpio_set(struct gpio_chip *gc, unsigned int off, int val)
 	struct attiny_lcd *state = gpiochip_get_data(gc);
 	u8 last_val;
 
-	mutex_lock(&state->lock);
+	guard(mutex)(&state->lock);
 
 	last_val = attiny_get_port_state(state, mappings[off].reg);
 	if (val)
@@ -239,8 +232,6 @@ static void attiny_gpio_set(struct gpio_chip *gc, unsigned int off, int val)
 
 		msleep(100);
 	}
-
-	mutex_unlock(&state->lock);
 }
 
 static int attiny_i2c_read(struct i2c_client *client, u8 reg, unsigned int *buf)