Re: [PATCH v2 2/4] docs: hwmon: (ltc2945): change type of val to ULL in ltc2945_val_to_reg()

[Alexandru Ardelean]

On Wed, Nov 11, 2020 at 4:54 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> On 11/11/20 1:12 AM, Alexandru Ardelean wrote:
> > In order to account for any potential overflows that could occur.
> >
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
>
> Thinking about it, this can only really happen if the user provides
> excessive values for limit attributes. Those are currently clamped
> later, after the conversion. I think it would be better to modify
> the code to apply a clamp _before_ the conversion as well instead
> of trying to solve the overflow problem with unsigned long long.
>
> Either case, can you send me a register dump for this chip ?

I asked Mark to help out on this.
Right now I don't have a board around my home-office.
I"m just pulling patches from our own tree to send upstream.
Is there a specific command you have in mind for this i2cdump?

Is the output of something like this fine:
# i2cdump -r 0x00-0x31 1 0x6f
?

We have a board that's being developed with this driver (and chip).
I think Mark will try to read values from the eval-board [since he has
one around].

Thanks
Alex

> I'd like to write a module test script to actually check if there
> are any over/underflows or other problems.
>
> Thanks,
> Guenter
>
> > ---
> >  drivers/hwmon/ltc2945.c | 12 ++++++------
> >  1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/hwmon/ltc2945.c b/drivers/hwmon/ltc2945.c
> > index 1cea710df668..6d4569a25471 100644
> > --- a/drivers/hwmon/ltc2945.c
> > +++ b/drivers/hwmon/ltc2945.c
> > @@ -155,7 +155,7 @@ static long long ltc2945_reg_to_val(struct device *dev, u8 reg)
> >  }
> >
> >  static int ltc2945_val_to_reg(struct device *dev, u8 reg,
> > -                           unsigned long val)
> > +                           unsigned long long val)
> >  {
> >       struct ltc2945_state *st = dev_get_drvdata(dev);
> >       struct regmap *regmap = st->regmap;
> > @@ -181,14 +181,14 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg,
> >                       return ret;
> >               if (control & CONTROL_MULT_SELECT) {
> >                       /* 25 mV * 25 uV = 0.625 uV resolution. */
> > -                     val = DIV_ROUND_CLOSEST(val, 625);
> > +                     val = DIV_ROUND_CLOSEST_ULL(val, 625);
> >               } else {
> >                       /*
> >                        * 0.5 mV * 25 uV = 0.0125 uV resolution.
> >                        * Divide first to avoid overflow;
> >                        * accept loss of accuracy.
> >                        */
> > -                     val = DIV_ROUND_CLOSEST(val, 25) * 2;
> > +                     val = DIV_ROUND_CLOSEST_ULL(val, 25) * 2;
> >               }
> >               break;
> >       case LTC2945_VIN_H:
> > @@ -197,7 +197,7 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg,
> >       case LTC2945_MAX_VIN_THRES_H:
> >       case LTC2945_MIN_VIN_THRES_H:
> >               /* 25 mV resolution. */
> > -             val /= 25;
> > +             val = div_u64(val, 25);
> >               break;
> >       case LTC2945_ADIN_H:
> >       case LTC2945_MAX_ADIN_H:
> > @@ -219,7 +219,7 @@ static int ltc2945_val_to_reg(struct device *dev, u8 reg,
> >                * dividing the reported current by the sense resistor value
> >                * in mOhm.
> >                */
> > -             val = DIV_ROUND_CLOSEST(val, 25);
> > +             val = DIV_ROUND_CLOSEST_ULL(val, 25);
> >               break;
> >       default:
> >               return -EINVAL;
> > @@ -247,7 +247,7 @@ static ssize_t ltc2945_value_store(struct device *dev,
> >       struct ltc2945_state *st = dev_get_drvdata(dev);
> >       struct regmap *regmap = st->regmap;
> >       u8 reg = attr->index;
> > -     unsigned long val;
> > +     unsigned long long val;
> >       u8 regbuf[3];
> >       int num_regs;
> >       int regval;
> >
>