Re: [PATCH] regulator (max5970): Add hwmon support

[Naresh Solanki]

Hi


On Thu, 31 Aug 2023 at 01:02, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> On 8/30/23 12:14, Naresh Solanki wrote:
> > Hi
> >
> [ ... ]
> >>> +                     /*
> >>> +                      * Calculate voltage from ADC value and MON range.
> >>> +                      * ddata->mon_rng holds the voltage corresponding to the maximum value the
> >>> +                      * 10-bit ADC can measure.
> >>> +                      * To obtain the output, multiply the ADC value by the MON range (in
> >>> +                      * microvolts) and then divide it by the maximum value of the 10-bit ADC.
> >>> +                      */
> >>> +                     *val = mul_u64_u32_shr(*val, ddata->mon_rng[channel], 10);
> >>
> >> Why do you use mul_u64_u32_shr() here but a direct shift above ?
> > There is possibility of overflow due to large value of ddata->mon_rng
>
> Does the right shift guarantee that the result fits into 32 bit ?
Yes. Value in ddata->mon_rng can go upto 26bits, & ADC is 10 bit.
The 10 bit right shift(part of calculation) makes sure the result
never exceed 32 bit

Regards,
Naresh
>
> Thanks,
> Guenter
>