On Thu, 27 Jun 2013 07:31:25 -0700, Guenter Roeck wrote:
> On Thu, Jun 27, 2013 at 10:36:31AM +0200, Jean Delvare wrote:
> > I'm once again late, but I could not find the time to test your ds1621
> > patches before today.
> >
> > On Wed, 8 May 2013 22:45:53 -0700, Robert Coulson wrote:
> > > --- a/drivers/hwmon/ds1621.c
> > > +++ b/drivers/hwmon/ds1621.c
> > > (...)
> > > +/*
> > > + * TEMP: 0.001C/bit (-55C to +125C)
> > > + * REG:
> > > + * - 1621, 1625: x = 0.5C
> > > + * - 1721: x = 0.0625C
> > > + * Assume highest resolution and let the bits fall where they may..
> > > + */
> > > +static inline u16 DS1621_TEMP_TO_REG(long temp)
> > > +{
> > > + int ntemp = clamp_val(temp, DS1621_TEMP_MIN, DS1621_TEMP_MAX);
> > > + ntemp += (ntemp < 0 ? -31 : 31);
> > > + ntemp = DIV_ROUND_CLOSEST(ntemp * 10, 625) << 4;
> > > + return (u16)ntemp;
> > > +}
> >
> > This breaks limit rounding on the DS1621. Limits have a resolution of
> > 0.5°C on that chip, so limit values should rounded to the closest
> > half-degree. It used to work but no longer: if I write 20300 to
> > temp1_min, it is rounded down to 20000, while it should be rounded up
> > to 20500.
> >
> My fault, since I proposed that approach. Didn't I have the same problem
> with some other driver ? Makes it even worse. I'll have to look up my notes.
Yes I am almost certain we discussed this very topic for another driver
recently, I think it was tmp401.
--
Jean Delvare
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