hwmon: (max1619) Clamp temperature range when writing limits

Module test code reports underflows when writing sensor limits.

temp2_min: Suspected underflow: [min=-77000, read 101000, written -2147483648]
temp2_max: Suspected underflow: [min=-77000, read 101000, written -2147483648]
temp2_crit: Suspected underflow: [min=-77000, read 101000, written -2147483648]

Clamp temperature ranges when writing limits to fix the problem.
While at it, use sign_extend32() when reading temperatures to make
the code easier to understand.
Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/max1619.c

@@ -52,16 +52,6 @@ static const unsigned short normal_i2c[] = {
  * Conversions
  */
 
-static int temp_from_reg(int val)
-{
-	return (val & 0x80 ? val-0x100 : val) * 1000;
-}
-
-static int temp_to_reg(int val)
-{
-	return (val < 0 ? val+0x100*1000 : val) / 1000;
-}
-
 enum temp_index {
 	t_input1 = 0,
 	t_input2,
@@ -142,7 +132,7 @@ static ssize_t temp_show(struct device *dev, struct device_attribute *devattr,
 	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
 	struct max1619_data *data = max1619_update_device(dev);
 
-	return sprintf(buf, "%d\n", temp_from_reg(data->temp[attr->index]));
+	return sprintf(buf, "%d\n", sign_extend(data->temp[attr->index], 7) * 1000);
 }
 
 static ssize_t temp_store(struct device *dev,
@@ -158,7 +148,7 @@ static ssize_t temp_store(struct device *dev,
 		return err;
 
 	mutex_lock(&data->update_lock);
-	data->temp[attr->index] = temp_to_reg(val);
+	data->temp[attr->index] = DIV_ROUND_CLOSEST(clamp_val(val, -128000, 127000), 1000);
 	i2c_smbus_write_byte_data(client, regs_write[attr->index],
 				  data->temp[attr->index]);
 	mutex_unlock(&data->update_lock);