Please suggest proper format for DT properties.

Hi,

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.

Quoted 25 lines · Constantine Shulyupin

Hi,

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.

Quoted 5 lines

nct7802 {
        compatible = "nuvoton,nct7802";
        reg = <0x2a>;
        nuvoton,sensors-types = "thermistor", "disabled", "voltage";
};

It seems you are just listing out all possible modes. Why do you need this in the DT at all? This can be inferred by the compatible string.

Quoted 10 lines

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.

I don't see how this relates to the first 2 options. The register you write selects the mode? In general, we don't want bindings of just random register writes.

Rob

Quoted 27 lines · Rob Herring

Quoted 25 lines · Constantine Shulyupin

Hi,

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.

Quoted 8 lines

Quoted 5 lines

nct7802 {
        compatible = "nuvoton,nct7802";
        reg = <0x2a>;
        nuvoton,sensors-types = "thermistor", "disabled", "voltage";
};

It seems you are just listing out all possible modes. Why do you need this in the DT at all? This can be inferred by the compatible string.

There are tree sensor, each of one can be one of three type ("thermal diode", "thermistor", "voltage") or be disabled.
Also there are at least five platform depended registers, most of them are enable/disable.
You can find full datasheet here
https://www.nuvoton.com/hq/products/cloud-computing/hardware-monitors/desktop-server-series/nct7802y/

The question is how to describe configuration of this registers in dts. The second option is array of types for tree registers.

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
};

Quoted 43 lines · 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:

Quoted 8 lines

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>;
	};
};

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

Quoted 4 lines

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:

Quoted 16 lines

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 ?