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hwmon: (sht15) Fix integer overflow in humidity calculation 

An integer overflow occurs in the calculation of RHlinear when the
relative humidity is greater than around 30%. The consequence is a subtle
(but noticeable) error in the resulting humidity measurement.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: stable@kernel.org
Cc: Jonathan Cameron <jic23@cam.ac.uk>
This commit is contained in:
Vivien Didelot 2011-03-21 17:59:35 +01:00 committed by Jean Delvare
parent 396bd766a6
commit ccd32e735d
1 changed files with 2 additions and 2 deletions
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4
drivers/hwmon/sht15.c
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@ -333,11 +333,11 @@ static inline int sht15_calc_humid(struct sht15_data *data)
const int c1 = -4; const int c1 = -4;
const int c2 = 40500; /* x 10 ^ -6 */ const int c2 = 40500; /* x 10 ^ -6 */
const int c3 = -2800; /* x10 ^ -9 */ const int c3 = -28; /* x 10 ^ -7 */
RHlinear = c1*1000 RHlinear = c1*1000
+ c2 * data->val_humid/1000 + c2 * data->val_humid/1000
+ (data->val_humid * data->val_humid * c3)/1000000; + (data->val_humid * data->val_humid * c3) / 10000;
return (temp - 25000) * (10000 + 80 * data->val_humid) return (temp - 25000) * (10000 + 80 * data->val_humid)
/ 1000000 + RHlinear; / 1000000 + RHlinear;
} }