On Thu, 14 Nov 2024 12:52:12 +0000, <Victor.Duicu@xxxxxxxxxxxxx> wrote: > On Thu, 2024-11-14 at 12:00 +0100, Matteo Martelli wrote: > > EXTERNAL EMAIL: Do not click links or open attachments unless you > > know the content is safe > > > > Hi Matteo, > > > On Thu, 14 Nov 2024 10:47:02 +0200, <victor.duicu@xxxxxxxxxxxxx> > > wrote: > > > From: Victor Duicu <victor.duicu@xxxxxxxxxxxxx> > > > > > > This patch implements ACPI support to Microchip pac1921. > > > The driver can read the shunt resistor value and label from the > > > ACPI table. > > > > > > Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx> > > > Signed-off-by: Victor Duicu <victor.duicu@xxxxxxxxxxxxx> > > > --- > > > > > .... > > > > > > > > > > +#define PAC1921_ACPI_GET_uOHMS_VALSÂ Â Â Â Â Â Â Â Â Â Â Â 0 > > > +#define PAC1921_ACPI_GET_LABELÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 1 > > > +/* > > > + * The maximum acceptable shunt value is 2146.999999 OHM. > > > + * This value, which is below INT_MAX, was chosen in order to > > > + * allow the readings from dt and ACPI to share the same range > > > + * and to simplify the checks. > > > + * With this value the maximum current that can be read is > > > + * 0.1V / 2146.999999OHM = 46.576 uA > > > + * If we use INT_MAX the maximum current that can be read is > > > + * 0.1V / 2147.483647OHM = 46.566 uA > > > + * The relative error between the two values is > > > + * |(46.566 - 46.576) / 46.566| * 100 = 0.0214 > > > + */ > > > +#define PAC1921_MAX_SHUNT_VALUE_uOHMSÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â 2146999999UL > > > + > > > > Just a minor point about this: if I understand correctly that value > > comes from (INT_MAX / MICRO - 1) * MICRO + MAX_MICRO. This was to > > simplify the check in a single statement in > > pac1921_write_shunt_resistor() > > which is called when the shunt resistor is set from *sysfs* (neither > > from DT nor ACPI). I'm fine with this value and the new check but I > > find > > the explanation comment a bit confusing. If you could come up with a > > bit > > more clear explanation about the reason of such value I think it > > would be > > better otherwise I am fine with it as it is. Also, maybe use the full > > room > > for 80 characters per line and UOHMS instead of uOHMS to avoid mixed > > case if > > you are going with a new version. > > We could completely remove the need to use a constant below INT_MAX > with this check in pac1921_write_shunt_resistor: > > if ((!val && !val_fract) ||Â > ((val >= INT_MAX / MICRO) && (val_fract > INT_MAX % MICRO))) > return -EINVAL; > > Do you agree with this approach? Yes, something like this would be clearer to me. Anyway, I think you also need to check for val > INT_MAX / MICRO when val_fract is < INT_MAX % MICRO, right? Also, I think you can remove a couple of parenthesis. So something like the following maybe (but please double check it): if ((!val && !val_fract) || val > INT_MAX / MICRO || (val == INT_MAX / MICRO && val_fract > INT_MAX % MICRO)) I think that usually it would be better to use pre-computed constants instead of run-time divisions for efficiency but since the shunt resistor is likely going to be set rarely, I would go for this code for better clarity. > Also, the use of mixed case was suggested by Andy to increase > readability. Ah, sorry for missing Andy's comment. I am fine with it if you also find it more readable. > > ... > > > > > > > Best regards, > > Matteo Martelli > > With Best Regards, > Duicu Victor Thanks, Matteo Martelli
