hwmon: (adt7475) Change update functions to add error handling

I2C SMBus sometimes returns error codes.
In the error case, measurement values are updated incorrectly.
The sensor application then generates warning log messages and SNMP traps.
To prevent this, add error handling into the update functions.

Signed-off-by: Tokunori Ikegami <ikegami@allied-telesis.co.jp>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Chris Packham <chris.packham@alliedtelesis.co.nz>
[groeck: Update description]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/adt7475.c

@@ -1384,63 +1384,119 @@ static void adt7475_remove_files(struct i2c_client *client,
 		sysfs_remove_group(&client->dev.kobj, &vid_attr_group);
 }
 
-static void adt7475_update_limits(struct i2c_client *client)
+static int adt7475_update_limits(struct i2c_client *client)
 {
 	struct adt7475_data *data = i2c_get_clientdata(client);
 	int i;
+	int ret;
 
-	data->config4 = adt7475_read(REG_CONFIG4);
-	data->config5 = adt7475_read(REG_CONFIG5);
+	ret = adt7475_read(REG_CONFIG4);
+	if (ret < 0)
+		return ret;
+	data->config4 = ret;
+
+	ret = adt7475_read(REG_CONFIG5);
+	if (ret < 0)
+		return ret;
+	data->config5 = ret;
 
 	for (i = 0; i < ADT7475_VOLTAGE_COUNT; i++) {
 		if (!(data->has_voltage & (1 << i)))
 			continue;
 		/* Adjust values so they match the input precision */
-		data->voltage[MIN][i] =
-			adt7475_read(VOLTAGE_MIN_REG(i)) << 2;
-		data->voltage[MAX][i] =
-			adt7475_read(VOLTAGE_MAX_REG(i)) << 2;
+		ret = adt7475_read(VOLTAGE_MIN_REG(i));
+		if (ret < 0)
+			return ret;
+		data->voltage[MIN][i] = ret << 2;
+
+		ret = adt7475_read(VOLTAGE_MAX_REG(i));
+		if (ret < 0)
+			return ret;
+		data->voltage[MAX][i] = ret << 2;
 	}
 
 	if (data->has_voltage & (1 << 5)) {
-		data->voltage[MIN][5] = adt7475_read(REG_VTT_MIN) << 2;
-		data->voltage[MAX][5] = adt7475_read(REG_VTT_MAX) << 2;
+		ret = adt7475_read(REG_VTT_MIN);
+		if (ret < 0)
+			return ret;
+		data->voltage[MIN][5] = ret << 2;
+
+		ret = adt7475_read(REG_VTT_MAX);
+		if (ret < 0)
+			return ret;
+		data->voltage[MAX][5] = ret << 2;
 	}
 
 	for (i = 0; i < ADT7475_TEMP_COUNT; i++) {
 		/* Adjust values so they match the input precision */
-		data->temp[MIN][i] =
-			adt7475_read(TEMP_MIN_REG(i)) << 2;
-		data->temp[MAX][i] =
-			adt7475_read(TEMP_MAX_REG(i)) << 2;
-		data->temp[AUTOMIN][i] =
-			adt7475_read(TEMP_TMIN_REG(i)) << 2;
-		data->temp[THERM][i] =
-			adt7475_read(TEMP_THERM_REG(i)) << 2;
-		data->temp[OFFSET][i] =
-			adt7475_read(TEMP_OFFSET_REG(i));
+		ret = adt7475_read(TEMP_MIN_REG(i));
+		if (ret < 0)
+			return ret;
+		data->temp[MIN][i] = ret << 2;
+
+		ret = adt7475_read(TEMP_MAX_REG(i));
+		if (ret < 0)
+			return ret;
+		data->temp[MAX][i] = ret << 2;
+
+		ret = adt7475_read(TEMP_TMIN_REG(i));
+		if (ret < 0)
+			return ret;
+		data->temp[AUTOMIN][i] = ret << 2;
+
+		ret = adt7475_read(TEMP_THERM_REG(i));
+		if (ret < 0)
+			return ret;
+		data->temp[THERM][i] = ret << 2;
+
+		ret = adt7475_read(TEMP_OFFSET_REG(i));
+		if (ret < 0)
+			return ret;
+		data->temp[OFFSET][i] = ret;
 	}
 	adt7475_read_hystersis(client);
 
 	for (i = 0; i < ADT7475_TACH_COUNT; i++) {
 		if (i == 3 && !data->has_fan4)
 			continue;
-		data->tach[MIN][i] =
-			adt7475_read_word(client, TACH_MIN_REG(i));
+		ret = adt7475_read_word(client, TACH_MIN_REG(i));
+		if (ret < 0)
+			return ret;
+		data->tach[MIN][i] = ret;
 	}
 
 	for (i = 0; i < ADT7475_PWM_COUNT; i++) {
 		if (i == 1 && !data->has_pwm2)
 			continue;
-		data->pwm[MAX][i] = adt7475_read(PWM_MAX_REG(i));
-		data->pwm[MIN][i] = adt7475_read(PWM_MIN_REG(i));
+		ret = adt7475_read(PWM_MAX_REG(i));
+		if (ret < 0)
+			return ret;
+		data->pwm[MAX][i] = ret;
+
+		ret = adt7475_read(PWM_MIN_REG(i));
+		if (ret < 0)
+			return ret;
+		data->pwm[MIN][i] = ret;
 		/* Set the channel and control information */
 		adt7475_read_pwm(client, i);
 	}
 
-	data->range[0] = adt7475_read(TEMP_TRANGE_REG(0));
-	data->range[1] = adt7475_read(TEMP_TRANGE_REG(1));
-	data->range[2] = adt7475_read(TEMP_TRANGE_REG(2));
+	ret = adt7475_read(TEMP_TRANGE_REG(0));
+	if (ret < 0)
+		return ret;
+	data->range[0] = ret;
+
+	ret = adt7475_read(TEMP_TRANGE_REG(1));
+	if (ret < 0)
+		return ret;
+	data->range[1] = ret;
+
+	ret = adt7475_read(TEMP_TRANGE_REG(2));
+	if (ret < 0)
+		return ret;
+	data->range[2] = ret;
+
+	return 0;
 }
 
 static int adt7475_probe(struct i2c_client *client,
@@ -1719,54 +1775,101 @@ static void adt7475_read_pwm(struct i2c_client *client, int index)
 	}
 }
 
-static void adt7475_update_measure(struct device *dev)
+static int adt7475_update_measure(struct device *dev)
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct adt7475_data *data = i2c_get_clientdata(client);
 	u16 ext;
 	int i;
+	int ret;
+
+	ret = adt7475_read(REG_STATUS2);
+	if (ret < 0)
+		return ret;
+	data->alarms = ret << 8;
 
-	data->alarms = adt7475_read(REG_STATUS2) << 8;
-	data->alarms |= adt7475_read(REG_STATUS1);
+	ret = adt7475_read(REG_STATUS1);
+	if (ret < 0)
+		return ret;
+	data->alarms |= ret;
+
+	ret = adt7475_read(REG_EXTEND2);
+	if (ret < 0)
+		return ret;
+
+	ext = (ret << 8);
+
+	ret = adt7475_read(REG_EXTEND1);
+	if (ret < 0)
+		return ret;
+
+	ext |= ret;
 
-	ext = (adt7475_read(REG_EXTEND2) << 8) |
-		adt7475_read(REG_EXTEND1);
 	for (i = 0; i < ADT7475_VOLTAGE_COUNT; i++) {
 		if (!(data->has_voltage & (1 << i)))
 			continue;
+		ret = adt7475_read(VOLTAGE_REG(i));
+		if (ret < 0)
+			return ret;
 		data->voltage[INPUT][i] =
-			(adt7475_read(VOLTAGE_REG(i)) << 2) |
+			(ret << 2) |
 			((ext >> (i * 2)) & 3);
 	}
 
-	for (i = 0; i < ADT7475_TEMP_COUNT; i++)
+	for (i = 0; i < ADT7475_TEMP_COUNT; i++) {
+		ret = adt7475_read(TEMP_REG(i));
+		if (ret < 0)
+			return ret;
 		data->temp[INPUT][i] =
-			(adt7475_read(TEMP_REG(i)) << 2) |
+			(ret << 2) |
 			((ext >> ((i + 5) * 2)) & 3);
+	}
 
 	if (data->has_voltage & (1 << 5)) {
-		data->alarms |= adt7475_read(REG_STATUS4) << 24;
-		ext = adt7475_read(REG_EXTEND3);
-		data->voltage[INPUT][5] = adt7475_read(REG_VTT) << 2 |
+		ret = adt7475_read(REG_STATUS4);
+		if (ret < 0)
+			return ret;
+		data->alarms |= ret << 24;
+
+		ret = adt7475_read(REG_EXTEND3);
+		if (ret < 0)
+			return ret;
+		ext = ret;
+
+		ret = adt7475_read(REG_VTT);
+		if (ret < 0)
+			return ret;
+		data->voltage[INPUT][5] = ret << 2 |
 			((ext >> 4) & 3);
 	}
 
 	for (i = 0; i < ADT7475_TACH_COUNT; i++) {
 		if (i == 3 && !data->has_fan4)
 			continue;
-		data->tach[INPUT][i] =
-			adt7475_read_word(client, TACH_REG(i));
+		ret = adt7475_read_word(client, TACH_REG(i));
+		if (ret < 0)
+			return ret;
+		data->tach[INPUT][i] = ret;
 	}
 
 	/* Updated by hw when in auto mode */
 	for (i = 0; i < ADT7475_PWM_COUNT; i++) {
 		if (i == 1 && !data->has_pwm2)
 			continue;
-		data->pwm[INPUT][i] = adt7475_read(PWM_REG(i));
+		ret = adt7475_read(PWM_REG(i));
+		if (ret < 0)
+			return ret;
+		data->pwm[INPUT][i] = ret;
 	}
 
-	if (data->has_vid)
-		data->vid = adt7475_read(REG_VID) & 0x3f;
+	if (data->has_vid) {
+		ret = adt7475_read(REG_VID);
+		if (ret < 0)
+			return ret;
+		data->vid = ret & 0x3f;
+	}
+
+	return 0;
 }
 
 static struct adt7475_data *adt7475_update_device(struct device *dev)