Commit 79536059 authored by Maud Spierings's avatar Maud Spierings Committed by Guenter Roeck
Browse files

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



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: default avatarMaud Spierings <maudspierings@gocontroll.com>
Link: https://lore.kernel.org/r/20250307-ntc_oob-v2-1-bba2d32b1a8e@gocontroll.com


Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent ee65d9e6

drivers/hwmon/ntc_thermistor.c

+7 −8
Original line number Diff line number Diff line
@@ -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;

}