linux-kernel - Re: [PATCH v2 01/14] thermal/core: Change thermal_zone_ops to thermal_sensor

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Date:   Sun, 26 Jun 2022 19:33:06 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...exp.org>
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Subject: Re: [PATCH v2 01/14] thermal/core: Change thermal_zone_ops to
 thermal_sensor_ops


Hi Rafael,

sorry for the delay, I was OoO.

On 17/05/2022 17:42, Rafael J. Wysocki wrote:
> On Sat, May 7, 2022 at 2:55 PM Daniel Lezcano <daniel.lezcano@...exp.org> wrote:
>>
>> A thermal zone is software abstraction of a sensor associated with
>> properties and cooling devices if any.
>>
>> The fact that we have thermal_zone and thermal_zone_ops mixed is
>> confusing and does not clearly identify the different components
>> entering in the thermal management process. A thermal zone appears to
>> be a sensor while it is not.
> 
> Well, the majority of the operations in thermal_zone_ops don't apply
> to thermal sensors.  For example, ->set_trips(), ->get_trip_type(),
> ->get_trip_temp().

The set_trips is necessary to set the sensor interrupt to fire when the 
trip temperature is crossed the way up or down.

>> In order to set the scene for multiple thermal sensors aggregated into
>> a single thermal zone. Rename the thermal_zone_ops to
>> thermal_sensor_ops, that will appear clearyl the thermal zone is not a
>> sensor but an abstraction of one [or multiple] sensor(s).
> 
> So I'm not convinced that the renaming mentioned above is particularly
> clean either.
> 
> IMV the way to go would be to split the thermal sensor operations,
> like ->get_temp(), out of thermal_zone_ops.

Probably, we should first replace all the calls to ops->get_temp with a 
function. Then create the ops for the sensor:

  - get_trend
  - get_temp
  - set_trips
  - bind / unbind

> But then it is not clear what a thermal zone with multiple sensors in
> it really means.  I guess it would require an aggregation function to
> combine the thermal sensors in it that would produce an effective
> temperature to check against the trip points.

Yes, that is why the above ops->get_temp should be wrapped into a 
function which can evolve to an aggregation function.

> Honestly, I don't think that setting a separate set of trips for each
> sensor in a thermal zone would make a lot of sense.

I agree the set_trips is for the interrupt mode only.


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