Re: [PATCH v2 2/2] hwmon: (max6621) fix negative temperature offset and crit readings

[Guenter Roeck]

On Mon, Aug 10, 2026 at 11:28:39AM +0700, Cong Nguyen wrote:
> max6621_read() reads the CONFIG2 offset and the critical alert threshold
> registers into a u32 and scales them without sign extension:
> 
> 	/* offset */ *val = (regval >> MAX6621_REG_TEMP_SHIFT) * 1000L;
> 	/* crit   */ *val = regval * 1000L;
> 
> Both attributes are writable and their write paths clamp to a negative
> minimum and encode negative values, so a value written as negative is read
> back as a large positive number. For example, writing a -10 degrees C
> offset stores max6621_temp_mc2reg(-10000) = (-10 << 6) = 0xfd80; the read
> then computes 0xfd80 >> 6 = 1014 -> 1014000 instead of -10000.
> 
> Cast the register value to s16 before scaling so the read preserves the
> sign the write path encodes. The temperature input path already uses an s8
> intermediate and is left unchanged.
> 
> Fixes: 92b64580f14b ("hwmon: (max6621) Add support for Maxim MAX6621 temperature sensor")
> Cc: stable@xxxxxxxxxxxxxxx
> Assisted-by: Claude:claude-opus-4
> Signed-off-by: Cong Nguyen <congnt264@xxxxxxxxx>

Applied.

Thanks,
Guenter