linux-kernel - Re: [PATCH v2 0/2] Add a generic virtual thermal sensor

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Message-ID: <c395abad-598b-c06a-9252-c8e62c977188@baylibre.com>
Date:   Mon, 20 Sep 2021 15:12:20 +0200
From:   Alexandre Bailon <abailon@...libre.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>, rui.zhang@...el.com,
        amitk@...nel.org
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        ben.tseng@...iatek.com, khilman@...libre.com, mka@...omium.org
Subject: Re: [PATCH v2 0/2] Add a generic virtual thermal sensor


On 9/17/21 4:03 PM, Daniel Lezcano wrote:
> On 17/09/2021 15:33, Alexandre Bailon wrote:
>> Hi Daniel,
>>
>> On 9/17/21 2:41 PM, Daniel Lezcano wrote:
>>> On 17/09/2021 09:27, Alexandre Bailon wrote:
>>>> This series add a virtual thermal sensor.
>>>> It could be used to get a temperature using some thermal sensors.
>>>> Currently, the supported operations are max, min and avg.
>>>> The virtual sensor could be easily extended to support others
>>>> operations.
>>>>
>>>> Note:
>>>> Currently, thermal drivers must explicitly register their sensors to
>>>> make them
>>>> available to the virtual sensor.
>>>> This doesn't seem a good solution to me and I think it would be
>>>> preferable to
>>>> update the framework to register the list of each available sensors.
>>> Why must the drivers do that ?
>> Because there are no central place where thermal sensor are registered.
>> The only other way I found was to update thermal_of.c,
>> to register the thermal sensors and make them available later to the
>> virtual thermal sensor.
>>
>> To work, the virtual thermal need to get the sensor_data the ops from
>> the thermal sensor.
>> And as far I know, this is only registered in thermal_of.c, in the
>> thermal zone data
>> but I can't access it directly from the virtual thermal sensor.
>>
>> How would you do it ?
> Via the phandles when registering the virtual sensor ?
As far I know, we can't get the ops or the sensor_data from the phandle 
of a thermal sensor.
The closest solution I found so far would be to aggregate the thermal 
zones instead of thermal sensors.
thermal_zone_device has the data needed and a thermal zone could be find 
easily using its name.

But, using a thermal_zone_device, I don't see how to handle module 
unloading.

Thanks,
Alexandre
> Or is the problem you are mentioning related to the sensor module
> loading after the virtual sensor ?
>