Proposal to change sensor interface to use double values

[Emily Shaffer]

Same, I'm ok with this.

On Mon, Aug 6, 2018 at 1:09 PM Patrick Venture <venture at google.com> wrote:

> On Mon, Aug 6, 2018 at 12:10 PM, James Feist
> <james.feist at linux.intel.com> wrote:
> > I've submitted a change to modify the sensor interface to remove scale,
> and
> > make the sensor value a double. The main reason for doing this is
> > simplification of the interface. In most usages, daemons pull the value,
> and
> > the scale, then immediately translate this value to a double. This could
> > easily be done once by the sensor producer instead of all daemons. The
> > counter example that was given was phosphor-fan-presence, but doing a
> quick
> > grep I can't find scale being used, so this might mean for a scaled fan
> you
> > have to factor that in to all configuration files, or scaled fans aren't
> > supported. The threshold interface is not usable independent from the
> value
> > interface, as the thresholds are affected by the same scale. Using a
> fixed
> > scale also won't work well for a logarithmic sensor, while floating point
> > would. Realistic precision should not be affected for any common sensor.
> We
> > also in the future may be interested in a daemon producing a threshold
> for a
> > sensor that another daemon owns. With the scale existing elsewhere, this
> > would not be trivial to map.
> >
> > Review for context: https://gerrit.openbmc-project.xyz/#/c/11739/
> >
> > This change is not ready to be submitted as is, but we would like to
> hear if
> > there are any major objections. If not, we would like to start an upgrade
> > path to support both interfaces until it is possible to make the switch.
> > Bmcweb already supports both. In most cases this is just pulling the
> value
> > using a visitor, and setting the scale to 0 if it does not exist. Max and
> > Min can also be used for IPMI scaling.
>
> I'm fine with this.  It saves everybody converting it to a double
> before using.  Further scaling, which can be necessary can be further
> done against the double.  For instance, with ipmi, to fit a value we
> sometimes scale again.
>
> >
> > Thanks,
> >
> > - James Feist
> >
> >
>
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