On Tue, Nov 15, 2016 at 02:25:11PM -0600, Rob Herring wrote:
> On Tue, Nov 15, 2016 at 1:52 PM, Clemens Gruber
> <clemens.gruber@xxxxxxxxxxxx> wrote:
> > Hi,
> >
> > I am preparing a patch for the ina2xx driver to allow configuring the
> > PGA bits (which define the shunt voltage range) and the BRNG bit (which
> > defines the bus voltage range) from the device tree.
> > We have multiple INA219 with different voltage ranges, so I can't just
> > change the hardcoded default in ina2xx.c
> > The ADC averaging setting should also be configurable.
> >
> > Now I am asking myself if I should create several new DT properties or
> > rather add one config-reg property to set a different default value for
> > the 16-bit configuration register (instead of the driver defaults of
> > 0x399F for the INA219 and 0x4527 for the INA226) ?
> >
> > Solution A:
>
> Generally, this is preferred.
>
> > ina219_foo: ina219@44 {
> > compatible = "ti,ina219";
> > reg = <0x44>;
> > shunt-resistor = <25000>;
> >
> > pga = <2>; /* PGA Gain /2 instead of the default /8 */
> > /* Note: Possible PGA Gain values are /1, /2, /4 and /8 */
> >
> > has-16v-brng; /* Bus voltage range of 16V instead of 32V */
> >
> > averaging = <128>; /* Average 128 samples */
> > };
> >
> > Should each of those also have a sysfs attribute?
>
> These should probably be in DT or in sysfs, but not both. The decision
> should be based on how are the settings picked: by the h/w design or
> an end user will want to modify them.
>
Agreed.
Guenter
> > Solution B:
> >
> > ina219_bar: ina219@45 {
> > compatible = "ti,ina219";
> > reg = <0x45>;
> > shunt-resistor = <25000>;
> >
> > config-reg = <0x019F>; /* PGA /1, BRNG = 16V, No averaging */
> > };
> >
> > Regards,
> > Clemens
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