[hwmon PATCH v2 2/8] hwmon: (adt7470) Fix cache updated before hardware write on I2C error

[Luiz Angelo Daros de Luca <luizluca@gmail.com>]

adt7470_temp_write() and adt7470_pwm_write() update the driver's
cached values (temp_min, temp_max, pwm_input, pwm_enable) before issuing
the corresponding regmap_write(), and never check whether the write
succeeded before committing that update. If the I2C transaction fails,
the function correctly propagates the error to the caller, but the cache
silently keeps the new value, which was never actually applied to the
hardware. Subsequent reads then report a value that does not match the
device state.

Reorder both write paths to update the cache only after a successful
regmap_write(), so the cache always reflects what was actually
written to the hardware.

Fixes: ef67959c4253 ("hwmon: (adt7470) Convert to use regmap")
Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
---
 drivers/hwmon/adt7470.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/hwmon/adt7470.c b/drivers/hwmon/adt7470.c
index 481d51617f4b..62ec68ea0a40 100644
--- a/drivers/hwmon/adt7470.c
+++ b/drivers/hwmon/adt7470.c
@@ -589,14 +589,16 @@ static int adt7470_temp_write(struct device *dev, u32 attr, int channel, long va
 	switch (attr) {
 	case hwmon_temp_min:
 		mutex_lock(&data->lock);
-		data->temp_min[channel] = val;
 		err = regmap_write(data->regmap, ADT7470_TEMP_MIN_REG(channel), val);
+		if (!err)
+			data->temp_min[channel] = val;
 		mutex_unlock(&data->lock);
 		break;
 	case hwmon_temp_max:
 		mutex_lock(&data->lock);
-		data->temp_max[channel] = val;
 		err = regmap_write(data->regmap, ADT7470_TEMP_MAX_REG(channel), val);
+		if (!err)
+			data->temp_max[channel] = val;
 		mutex_unlock(&data->lock);
 		break;
 	default:
@@ -831,9 +833,10 @@ static int adt7470_pwm_write(struct device *dev, u32 attr, int channel, long val
 	case hwmon_pwm_input:
 		val = clamp_val(val, 0, 255);
 		mutex_lock(&data->lock);
-		data->pwm[channel] = val;
 		err = regmap_write(data->regmap, ADT7470_REG_PWM(channel),
-				   data->pwm[channel]);
+				   val);
+		if (!err)
+			data->pwm[channel] = val;
 		mutex_unlock(&data->lock);
 		break;
 	case hwmon_pwm_enable:
@@ -847,10 +850,11 @@ static int adt7470_pwm_write(struct device *dev, u32 attr, int channel, long val
 		val--;
 
 		mutex_lock(&data->lock);
-		data->pwm_automatic[channel] = val;
 		err = regmap_update_bits(data->regmap, ADT7470_REG_PWM_CFG(channel),
 					 pwm_auto_reg_mask,
 					 val ? pwm_auto_reg_mask : 0);
+		if (!err)
+			data->pwm_automatic[channel] = val;
 		mutex_unlock(&data->lock);
 		break;
 	case hwmon_pwm_freq:

-- 
2.55.0