Re: [PATCH v3 2/4] hwmon: (aquacomputer_d5next) Avoid truncating scaled sensor readings

[Guenter Roeck <linux@roeck-us.net>]

On 9/14/26 16:37, Vas Zayarskiy wrote:
> High Flow Next power is reported in watts. Multiplying the 16-bit value
> by one million can overflow both the signed intermediate and the u32
> cache. Store power in long, perform the conversion in u64, and clamp to
> LONG_MAX. The other existing power conversions fit in a signed 32-bit
> value. Return ENODATA for unavailable power instead of exposing the

-ENODATA

> stored error as a reading.
> 
> Widen the shared current cache to u32. The Aquastream XT calibration can
> exceed 65535 mA; clamp its negative calibration results to zero before

That isn't a calibration. It is a conversion or scaling to hwmon ABI units.

> assigning to the unsigned cache. This also permits devices with scaled
> aggregate currents to store milliamperes directly.
> 
> Assisted-by: LLM sparse
> Signed-off-by: Vas Zayarskiy <contact@vasily.cc>
> ---
>   drivers/hwmon/aquacomputer_d5next.c | 12 ++++++++----
>   1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hwmon/aquacomputer_d5next.c b/drivers/hwmon/aquacomputer_d5next.c
> index 1ca70e726..9178ac4cb 100644
> --- a/drivers/hwmon/aquacomputer_d5next.c
> +++ b/drivers/hwmon/aquacomputer_d5next.c
> @@ -19,6 +19,7 @@
>   #include <linux/hwmon.h>
>   #include <linux/jiffies.h>
>   #include <linux/ktime.h>
> +#include <linux/limits.h>
>   #include <linux/module.h>
>   #include <linux/seq_file.h>
>   #include <linux/unaligned.h>
> @@ -599,9 +600,9 @@ struct aqc_data {
>   	u32 speed_input_min[1];
>   	u32 speed_input_target[1];
>   	u32 speed_input_max[1];
> -	u32 power_input[8];
> +	long power_input[8];
>   	u16 voltage_input[8];
> -	u16 current_input[8];
> +	u32 current_input[8];
>   
>   	/* Label values */
>   	const char *const *temp_label;
> @@ -976,7 +977,7 @@ static int aqc_legacy_read(struct aqc_data *priv)
>   
>   		/* Calculation derived from linear regression */
>   		sensor_value = get_unaligned_le16(priv->buffer + AQUASTREAMXT_PUMP_CURR_OFFSET);
> -		priv->current_input[0] = DIV_ROUND_CLOSEST(sensor_value * 176, 100) - 52;
> +		priv->current_input[0] = max(DIV_ROUND_CLOSEST(sensor_value * 176, 100) - 52, 0);
>   
>   		sensor_value = get_unaligned_le16(priv->buffer + AQUASTREAMXT_PUMP_VOLTAGE_OFFSET);
>   		priv->voltage_input[0] = DIV_ROUND_CLOSEST(sensor_value * 1000, 61);
> @@ -1070,6 +1071,8 @@ static int aqc_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
>   		}
>   		break;
>   	case hwmon_power:
> +		if (priv->power_input[channel] == -ENODATA)
> +			return -ENODATA;
>   		*val = priv->power_input[channel];
>   		break;
>   	case hwmon_pwm:
> @@ -1426,7 +1429,8 @@ static int aqc_raw_event(struct hid_device *hdev, struct hid_report *report, u8
>   			priv->power_input[0] = -ENODATA;
>   		else
>   			priv->power_input[0] =
> -			    get_unaligned_be16(data + HIGHFLOWNEXT_POWER) * 1000000;
> +			    min_t(u64, get_unaligned_be16(data + HIGHFLOWNEXT_POWER) * 1000000ULL,
> +				  LONG_MAX);
>   
>   		priv->voltage_input[0] = get_unaligned_be16(data + HIGHFLOWNEXT_5V_VOLTAGE) * 10;
>   		priv->voltage_input[1] =