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hwmon: (ntc_thermistor) return error instead of clipping on OOB

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When the ntc is reading Out Of Bounds instead of clipping to the nearest
limit (min/max) return -ENODATA. This prevents malfunctioning sensors
from sending a device into a shutdown loop due to a critical trip.

This implementation will only work for ntc type thermistors if a ptc
type is to be implemented the min/max ohm calculation must be adjusted
to take that into account.

Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
Link: https://lore.kernel.org/r/20250307-ntc_oob-v2-1-bba2d32b1a8e@gocontroll.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Maud Spierings
2025-03-07 09:10:43 +01:00
committed by Guenter Roeck
parent ee65d9e630
commit 7953605976
1 changed files with 7 additions and 8 deletions
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15
drivers/hwmon/ntc_thermistor.c
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@@ -387,12 +387,9 @@ static int get_ohm_of_thermistor(struct ntc_data *data, unsigned int uv)
puo = data->pullup_ohm;
pdo = data->pulldown_ohm;
if (uv == 0)
return (data->connect == NTC_CONNECTED_POSITIVE) ?
INT_MAX : 0;
if (uv >= puv)
return (data->connect == NTC_CONNECTED_POSITIVE) ?
0 : INT_MAX;
/* faulty adc value */
if (uv == 0 || uv >= puv)
return -ENODATA;
if (data->connect == NTC_CONNECTED_POSITIVE && puo == 0)
n = div_u64(pdo * (puv - uv), uv);
@@ -404,8 +401,10 @@ static int get_ohm_of_thermistor(struct ntc_data *data, unsigned int uv)
else
n = div64_u64_safe(pdo * puo * uv, pdo * (puv - uv) - puo * uv);
if (n > INT_MAX)
n = INT_MAX;
/* sensor out of bounds */
if (n > data->comp[0].ohm || n < data->comp[data->n_comp - 1].ohm)
return -ENODATA;
return n;
}