[PATCH 02/11] hwmon: (max6650) Introduce pwm_to_dac and dac_to_pwm

[Guenter Roeck <linux@roeck-us.net>]

Consolidate conversion from pwm value to dac value and from dac value
to pwm value into helper functions.

While doing this, only update the cached dac value if writing it to
the chip was successful after an update. Also, put macro argument of
DIV_FROM_REG() into ().

Cc: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/max6650.c | 53 ++++++++++++++++++++++++-------------------------
 1 file changed, 26 insertions(+), 27 deletions(-)

diff --git a/drivers/hwmon/max6650.c b/drivers/hwmon/max6650.c
index 6cce199dab6a..b6b8f8edc1b0 100644
--- a/drivers/hwmon/max6650.c
+++ b/drivers/hwmon/max6650.c
@@ -105,7 +105,8 @@ module_param(clock, int, 0444);
 #define FAN_RPM_MIN 240
 #define FAN_RPM_MAX 30000
 
-#define DIV_FROM_REG(reg) (1 << (reg & 7))
+#define DIV_FROM_REG(reg)	(1 << ((reg) & 7))
+#define DAC_LIMIT(v12)		((v12) ? 180 : 76)
 
 /*
  * Client data (each client gets its own)
@@ -150,6 +151,22 @@ static const struct of_device_id __maybe_unused max6650_dt_match[] = {
 };
 MODULE_DEVICE_TABLE(of, max6650_dt_match);
 
+static int dac_to_pwm(int dac, bool v12)
+{
+	/*
+	 * Useful range for dac is 0-180 for 12V fans and 0-76 for 5V fans.
+	 * Lower DAC values mean higher speeds.
+	 */
+	return clamp_val(255 - (255 * dac) / DAC_LIMIT(v12), 0, 255);
+}
+
+static u8 pwm_to_dac(unsigned int pwm, bool v12)
+{
+	int limit = DAC_LIMIT(v12);
+
+	return limit - (limit * pwm) / 255;
+}
+
 static struct max6650_data *max6650_update_device(struct device *dev)
 {
 	struct max6650_data *data = dev_get_drvdata(dev);
@@ -357,22 +374,10 @@ static ssize_t fan1_target_store(struct device *dev,
 static ssize_t pwm1_show(struct device *dev, struct device_attribute *devattr,
 			 char *buf)
 {
-	int pwm;
 	struct max6650_data *data = max6650_update_device(dev);
 
-	/*
-	 * Useful range for dac is 0-180 for 12V fans and 0-76 for 5V fans.
-	 * Lower DAC values mean higher speeds.
-	 */
-	if (data->config & MAX6650_CFG_V12)
-		pwm = 255 - (255 * (int)data->dac)/180;
-	else
-		pwm = 255 - (255 * (int)data->dac)/76;
-
-	if (pwm < 0)
-		pwm = 0;
-
-	return sprintf(buf, "%d\n", pwm);
+	return sprintf(buf, "%d\n", dac_to_pwm(data->dac,
+					       data->config & MAX6650_CFG_V12));
 }
 
 static ssize_t pwm1_store(struct device *dev,
@@ -383,6 +388,7 @@ static ssize_t pwm1_store(struct device *dev,
 	struct i2c_client *client = data->client;
 	unsigned long pwm;
 	int err;
+	u8 dac;
 
 	err = kstrtoul(buf, 10, &pwm);
 	if (err)
@@ -391,13 +397,10 @@ static ssize_t pwm1_store(struct device *dev,
 	pwm = clamp_val(pwm, 0, 255);
 
 	mutex_lock(&data->update_lock);
-
-	if (data->config & MAX6650_CFG_V12)
-		data->dac = 180 - (180 * pwm)/255;
-	else
-		data->dac = 76 - (76 * pwm)/255;
-	err = i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, data->dac);
-
+	dac = pwm_to_dac(pwm, data->config & MAX6650_CFG_V12);
+	err = i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, dac);
+	if (!err)
+		data->dac = dac;
 	mutex_unlock(&data->update_lock);
 
 	return err < 0 ? err : count;
@@ -728,11 +731,7 @@ static int max6650_set_cur_state(struct thermal_cooling_device *cdev,
 
 	mutex_lock(&data->update_lock);
 
-	if (data->config & MAX6650_CFG_V12)
-		data->dac = 180 - (180 * state)/255;
-	else
-		data->dac = 76 - (76 * state)/255;
-
+	data->dac = pwm_to_dac(state, data->config & MAX6650_CFG_V12);
 	err = i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, data->dac);
 
 	if (!err) {
-- 
2.7.4