On Tue, Sep 14, 2021 at 08:41:36AM -0400, Oskar Senft wrote:

Hi Guenter

quoted

https://lore.kernel.org/linux-hwmon/cover.1631021349.git.krzysztof.adamski@nokia.com/ (local)

That specifically includes the ability to enable or disable channels
using the standard 'status' property. While that series is primarily
for the n-factor property supported by the tmp421, the same approach
can be used for [temperature] sensor properties on other chips as well.

Good pointer! I should be able to replicate that for the LTD (@0) and
RTDs (1, 2, 3) in a similar way.

quoted

I put [temperature] in [] because we'd need to find a means to express
if the sub-nodes are for temperature, voltage, or something else, but
I think the basic principle is sound.

Following the example from tmp421, this could then be like this:

Something like that, only we'll need something to distinguish
temperature sensors from other sensor types, eg voltage or current.
Maybe a "type" property. I'd suggest "sensor-type", but we have
non-sensor attributes such as fan count and pwm values which should
be covered as well. But it looks like a good start for a set of
generic sensor properties.

i2c {
    #address-cells = <1>;
    #size-cells = <0>;

    nct7802@28 {
        compatible = "nuvoton,nct7802";
        reg = <0x28>;
        #address-cells = <1>;
        #size-cells = <0>;

        /* LTD */
        input@0 {
            reg = <0x0>;
            status = "okay";

Not sure what the default is here ('okay' or 'disabled').
We'd also need to define what to do if there is no data
for a given sensor.

            /* No "mode" attribute here*/
            label = "local temp";
        };

        /* RTD1 */
        input@1 {
            reg = <0x1>;
            mode = <0x2>; /* 3904 transistor */
            label = "voltage mode";

That isn't the idea for "label", as "label" would be expected to
show up as tempX_label (and a label of "voltage mode" would be odd).
The label should indicate where the sensor is located on a board,
such as "inlet" or "outlet".

        };

        input@2 {
            reg = <0x2>;
            mode = <0x4>; /* thermistor */
            label = "thermistor mode";
        };

        /* RTD3 */
        input@3 {
            reg = <0x3>;
            mode = <0x3>; /* thermal diode */
            label = "current mode";
            status = "disabled";
        };
    };
};

I noticed that "nct7802_temp_is_visible" only allows the temperature
sensor to be visible for current and thermistor but not voltage. Is
that right?

No, that is a bug.

Before I go and change the driver further, I'd like to make sure we
agree on the interface.

Also: Is nct7802_temp_is_visible called again after temp_type_store
was called (I didn't try it)?

No. That would not be the idea. If enabling / disabling a sensor
is supposed with the _enable attribute (and/or with devicetree),
the affected sensor should always be instantiated, and reading
sensor data should return -ENODATA if the sensor is disabled.

Thanks,
Guenter