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hwmon: (sht15) Fix sht15_calc_temp interpolation function 

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>
Cc: stable@kernel.org
This commit is contained in:
Jerome Oufella 2010-04-14 16:14:07 +02:00 committed by Jean Delvare
parent 2ba3abd818
commit 328a2c22ab
1 changed files with 3 additions and 3 deletions
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6
drivers/hwmon/sht15.c
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@ -303,13 +303,13 @@ error_ret:
**/ **/
static inline int sht15_calc_temp(struct sht15_data *data) static inline int sht15_calc_temp(struct sht15_data *data)
{ {
int d1 = 0; int d1 = temppoints[0].d1;
int i; int i;
for (i = 1; i < ARRAY_SIZE(temppoints); i++) for (i = ARRAY_SIZE(temppoints) - 1; i > 0; i--)
/* Find pointer to interpolate */ /* Find pointer to interpolate */
if (data->supply_uV > temppoints[i - 1].vdd) { 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].d1 - temppoints[i - 1].d1)
/ (temppoints[i].vdd - temppoints[i - 1].vdd) / (temppoints[i].vdd - temppoints[i - 1].vdd)
+ temppoints[i - 1].d1; + temppoints[i - 1].d1;