Re: Please suggest proper format for DT properties.

[Guenter Roeck]

On 09/22/2015 01:36 AM, Arnd Bergmann wrote:
> On Saturday 19 September 2015 01:36:43 Constantine Shulyupin wrote:
> > I am designing DT support for a hwmon chip.
> > It has some sensors, each of them can be:
> >   - "disabled"
> >   - "thermal diode"
> >   - "thermistor"
> >   - "voltage"
> >
> > Four possible options for DT properties format.
> >
> > Option 1: Separated property for each sensor.
> >
> > Example nct7802 node:
> >
> > nct7802 {
> >          compatible = "nuvoton,nct7802";
> >          reg = <0x2a>;
> >          nuvoton,sensor1-type = "thermistor";
> >          nuvoton,sensor2-type = "disabled";
> >          nuvoton,sensor3-type = "voltage";
> > };
> >
> > Option 2: Array of strings for all sensors.
> >
> > nct7802 {
> >          compatible = "nuvoton,nct7802";
> >          reg = <0x2a>;
> >          nuvoton,sensors-types = "thermistor", "disabled", "voltage";
> > };
> >
> > Option 3: Sets of 4 cells.
> >
> >    Borrowed from marvell,reg-init and broadcom,c45-reg-init.
> >
> >    The first cell is the page address,
> >    the second a register address within the page,
> >    the third cell contains a mask to be ANDed with the existing register
> >    value, and the fourth cell is ORed with the result to yield the
> >    new register value. If the third cell has a value of zero,
> >    no read of the existing value is performed.
> >
> > Example nct7802 node:
> >
> > nct7802 {
> >          compatible = "nuvoton,nct7802";
> >          reg = <0x2a>;
> >          nct7802,reg-init =
> >                  <0 0x21 0 0x01 > // START = 1
> >                  <0 0x22 0x03 0x02>; // RTD1_MD = 2
> > };
>
> I would strongly prefer Option 1 or 2 over option 3.
> Between 1 and 2, I'd probably go for 1. Another option might
> be to have a subnode per sensor:
>
> nct7802@2a {
>          compatible = "nuvoton,nct7802";
>          reg = <0x2a>;
> 	#address-cells=<1>;
> 	#size-cells=<0>;
>
> 	sensor@1 {
> 		compatible = "nuvoton,nct7802-thermistor";
> 		further-properties;
> 	};
> 	sensor@3 {
> 		compatible = "nuvoton,nct7802-voltage";
> 		for-example-range-mv = <0 5000>;
> 	};
> };
I personally would prefer this approach. It would also make it easier to add more
properties. Wonder what is more appropriate, though - a compatible property or
something like the following ?
		sensor-type = "xxx";

I don't have a preference, just asking.

Also, would the index be derived from "@1", or should there be a reg property ?

> In either case, I'd say that disabled sensors should not need to
> be listed.
Agreed.

Thanks,
Guenter

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