Re: [PATCH v2 3/9] hwmon: adm1275: Detect coefficient overflow

[Guenter Roeck]

On Fri, Jun 26, 2026 at 10:23:58AM +0300, Matti Vaittinen wrote:
> From: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
> 
> Sashiko detected potential coefficient overflow if large shunt resistor
> is used. When going unnoticed it can cause "drastically incorrect
> telemetry scaling factors" as Sashiko put it.
> 
> I am not convinced such "drastically incorrect telemetry scaling
> factors" could have gone unnoticed, so I suspect such large shunt
> resistors aren't really used. Well, it shouldn't hurt to detect the
> error and abort the probe before Really Wrong current / power -values
> are reported to user by the hwmon.
> 
> Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
> ---
> Revision history:
> v1 => v2:
>  - New patch
> 
> This patch returns -EOVERFLOW with an error print if overflow is
> detected. IF there really are systems where the overflow truly occurs,
> then this change will cause the probe to fail - which might hurt the
> boot process. It might be safer to only print the warning. One could
> also try changing the order of the shunt resistor value division (/1000)
> and the multiplication and see if overflow goes away - but it'll be
> somewhat more complex then. Hence, I just decided to error-out if this
> happens, and leave this for the people facing the real overflow to fix
> (if needed)... It's still fair to mention this might cause issues.

Let's see if it happens.

Applied.

Thanks,
Guenter