Re: [PATCH v2] hwmon: (nct7802) Fix overflows seen when writing into limit attributes

[Jean Delvare <jdelvare@suse.de>]

On Mon, 12 Dec 2016 06:14:14 -0800, Guenter Roeck wrote:
> Hi Jean,
> 
> On 12/12/2016 02:03 AM, Jean Delvare wrote:
> > On Fri,  9 Dec 2016 12:41:02 -0800, Guenter Roeck wrote:
> >> Fix overflows seen when writing voltage and temperature limit attributes.
> >>
> >> The value passed to DIV_ROUND_CLOSEST() needs to be clamped, and the
> >> value parameter passed to nct7802_write_fan_min() is an unsigned long.
> >>
> >> Also, writing values larger than 2700000 into a limit attribute results
> >> in writing 0 into the chip's limit registers.
> >
> > You are only talking about _fan_ limits, right?
> >
> Yes. I'll clarify.
> 
> >> The exact behavior when
> >> writing this value is unspecified. For consistency, report a limit of
> >> 1350000 if the chip register reads 0.  This may be wrong, and the chip
> >> behavior should be verified with the actual chip, but it is better than
> >> reporting a value of 0 (which, if written, results in writing a value
> >> of 0x1fff into the chip register).
> >
> > This fix is good by doesn't seem to be related with the overflows?
> >
> Writing a limit larger than 2700000 results in writing 0 into the register,
> which is reported back as 0. 2699999 -> 1 -> 1350000, 2700000 -> 0 -> 0.
> I consider that an overflow situation.

OK, I understand, you are right.

-- 
Jean Delvare
SUSE L3 Support