hwmon: (pwm-fan) Extract __set_pwm() function to only modify PWM duty cycle

It was necessary to decouple code handling writing to sysfs from the one
responsible for setting PWM of the fan.
Due to that, new __set_pwm() method was extracted, which is responsible for
only setting new PWM duty cycle.

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pwm-fan.c

@@ -33,20 +33,14 @@ struct pwm_fan_ctx {
 	unsigned char pwm_value;
 };
 
-static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
-		       const char *buf, size_t count)
+static int  __set_pwm(struct pwm_fan_ctx *ctx, unsigned long pwm)
 {
-	struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
-	unsigned long pwm, duty;
-	ssize_t ret;
-
-	if (kstrtoul(buf, 10, &pwm) || pwm > MAX_PWM)
-		return -EINVAL;
+	unsigned long duty;
+	int ret = 0;
 
 	mutex_lock(&ctx->lock);
-
 	if (ctx->pwm_value == pwm)
-		goto exit_set_pwm_no_change;
+		goto exit_set_pwm_err;
 
 	if (pwm == 0) {
 		pwm_disable(ctx->pwm);
@@ -66,13 +60,28 @@ static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
 
 exit_set_pwm:
 	ctx->pwm_value = pwm;
-exit_set_pwm_no_change:
-	ret = count;
 exit_set_pwm_err:
 	mutex_unlock(&ctx->lock);
 	return ret;
 }
 
+static ssize_t set_pwm(struct device *dev, struct device_attribute *attr,
+		       const char *buf, size_t count)
+{
+	struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
+	unsigned long pwm;
+	int ret;
+
+	if (kstrtoul(buf, 10, &pwm) || pwm > MAX_PWM)
+		return -EINVAL;
+
+	ret = __set_pwm(ctx, pwm);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
 static ssize_t show_pwm(struct device *dev,
 			struct device_attribute *attr, char *buf)
 {