6.6-stable review patch. If anyone has any objections, please let me know.
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From: David Lechner dlechner@baylibre.com
[ Upstream commit e2c68cea431d65292b592c9f8446c918d45fcf78 ]
Fix several issues with division of negative numbers in the tmp513 driver.
The docs on the DIV_ROUND_CLOSEST macro explain that dividing a negative value by an unsigned type is undefined behavior. The driver was doing this in several places, i.e. data->shunt_uohms has type of u32. The actual "undefined" behavior is that it converts both values to unsigned before doing the division, for example:
int ret = DIV_ROUND_CLOSEST(-100, 3U);
results in ret == 1431655732 instead of -33.
Furthermore the MILLI macro has a type of unsigned long. Multiplying a signed long by an unsigned long results in an unsigned long.
So, we need to cast both MILLI and data data->shunt_uohms to long when using the DIV_ROUND_CLOSEST macro.
Fixes: f07f9d2467f4 ("hwmon: (tmp513) Use SI constants from units.h") Fixes: 59dfa75e5d82 ("hwmon: Add driver for Texas Instruments TMP512/513 sensor chips.") Signed-off-by: David Lechner dlechner@baylibre.com Link: https://lore.kernel.org/r/20250114-fix-si-prefix-macro-sign-bugs-v1-1-696fd8... [groeck: Drop some continuation lines] Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/hwmon/tmp513.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/hwmon/tmp513.c b/drivers/hwmon/tmp513.c index 070f93226ed69..62d31aadda4bb 100644 --- a/drivers/hwmon/tmp513.c +++ b/drivers/hwmon/tmp513.c @@ -203,7 +203,8 @@ static int tmp51x_get_value(struct tmp51x_data *data, u8 reg, u8 pos, *val = sign_extend32(regval, reg == TMP51X_SHUNT_CURRENT_RESULT ? 16 - tmp51x_get_pga_shift(data) : 15); - *val = DIV_ROUND_CLOSEST(*val * 10 * MILLI, data->shunt_uohms); + *val = DIV_ROUND_CLOSEST(*val * 10 * (long)MILLI, (long)data->shunt_uohms); + break; case TMP51X_BUS_VOLTAGE_RESULT: case TMP51X_BUS_VOLTAGE_H_LIMIT: @@ -219,7 +220,7 @@ static int tmp51x_get_value(struct tmp51x_data *data, u8 reg, u8 pos, case TMP51X_BUS_CURRENT_RESULT: // Current = (ShuntVoltage * CalibrationRegister) / 4096 *val = sign_extend32(regval, 15) * (long)data->curr_lsb_ua; - *val = DIV_ROUND_CLOSEST(*val, MILLI); + *val = DIV_ROUND_CLOSEST(*val, (long)MILLI); break; case TMP51X_LOCAL_TEMP_RESULT: case TMP51X_REMOTE_TEMP_RESULT_1: @@ -259,7 +260,7 @@ static int tmp51x_set_value(struct tmp51x_data *data, u8 reg, long val) * The user enter current value and we convert it to * voltage. 1lsb = 10uV */ - val = DIV_ROUND_CLOSEST(val * data->shunt_uohms, 10 * MILLI); + val = DIV_ROUND_CLOSEST(val * (long)data->shunt_uohms, 10 * (long)MILLI); max_val = U16_MAX >> tmp51x_get_pga_shift(data); regval = clamp_val(val, -max_val, max_val); break;