hwmon: (sht15) Fix sht15_calc_temp interpolation function

commit 328a2c22abd08911e37fa66f1358f829cecd72e9 upstream.

I discovered two issues.
First the previous sht15_calc_temp() loop did not iterate through the
temppoints array since the (data->supply_uV > temppoints[i - 1].vdd)
test is always true in this direction.

Also the two-points linear interpolation function was returning biased
values due to a stray division by 1000 which shouldn't be there.

[JD: Also change the default value for d1 from 0 to something saner.]

Signed-off-by: Jerome Oufella <jerome.oufella@savoirfairelinux.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/hwmon/sht15.c b/drivers/hwmon/sht15.c
index 864a371f6eb98443f0565b1d1263cb66a370e152..bf41d4e6e5ac34eba0c634238051e5820edcf879 100644 (file)
--- a/drivers/hwmon/sht15.c
+++ b/drivers/hwmon/sht15.c
@@ -302,13 +302,13 @@ error_ret:
  **/
 static inline int sht15_calc_temp(struct sht15_data *data)
 {
-       int d1 = 0;
+       int d1 = temppoints[0].d1;
        int i;
 
-       for (i = 1; i < ARRAY_SIZE(temppoints); i++)
+       for (i = ARRAY_SIZE(temppoints) - 1; i > 0; i--)
                /* Find pointer to interpolate */
                if (data->supply_uV > temppoints[i - 1].vdd) {
-                       d1 = (data->supply_uV/1000 - temppoints[i - 1].vdd)
+                       d1 = (data->supply_uV - temppoints[i - 1].vdd)
                                * (temppoints[i].d1 - temppoints[i - 1].d1)
                                / (temppoints[i].vdd - temppoints[i - 1].vdd)
                                + temppoints[i - 1].d1;