Re: [PATCH v2 2/2] hwmon: (pmbus/ina233) Handle sign extension for negative shunt voltage

[Guenter Roeck]

On 3/18/26 12:40, Pradhan, Sanman wrote:
> From: Sanman Pradhan <psanman@xxxxxxxxxxx>
>
> ina233_read_word_data() reads MFR_READ_VSHUNT, which is a 16-bit
> two's complement value. Because pmbus_read_word_data() returns an
> integer, negative voltages (values > 32767) are currently treated as
> large positive values, leading to incorrect scaling in DIV_ROUND_CLOSEST().
>
> Add a cast to (s16) to ensure negative shunt voltages are correctly
> sign-extended before the scaling calculation is performed.
>
> Fixes: b64b6cb163f16 ("hwmon: Add driver for TI INA233 Current and Power Monitor")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Sanman Pradhan <psanman@xxxxxxxxxxx>
> ---
> v2:
>    - Added (s16) cast to fix sign-extension for negative shunt voltages,
>      complementing the error check fix applied in v1
> ---
>   drivers/hwmon/pmbus/ina233.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hwmon/pmbus/ina233.c b/drivers/hwmon/pmbus/ina233.c
> index dde1e16783943..819f4e8aeab61 100644
> --- a/drivers/hwmon/pmbus/ina233.c
> +++ b/drivers/hwmon/pmbus/ina233.c
> @@ -70,7 +70,7 @@ static int ina233_read_word_data(struct i2c_client *client, int page,
>   
>   		/* Adjust returned value to match VIN coefficients */
>   		/* VIN: 1.25 mV VSHUNT: 2.5 uV LSB */
> -		ret = DIV_ROUND_CLOSEST(ret * 25, 12500);
> +		ret = DIV_ROUND_CLOSEST((s16)ret * 25, 12500);

This may end up reporting a negative error value to the caller.
Should the result be masked against 0xffff ?

Thanks,
Guenter