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SubjectRe: Please suggest proper format for DT properties.
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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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