On 9/22/21 10:10 AM, Daniel Lezcano wrote:

On 20/09/2021 15:12, Alexandre Bailon wrote:

quoted

On 9/17/21 4:03 PM, Daniel Lezcano wrote:

quoted

On 17/09/2021 15:33, Alexandre Bailon wrote:

quoted

Hi Daniel,

On 9/17/21 2:41 PM, Daniel Lezcano wrote:

quoted

On 17/09/2021 09:27, Alexandre Bailon wrote:

quoted

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.

Yeah, the concept of the thermal zone and the sensor are very close.

There is the function in thermal_core.h:

  -> for_each_thermal_zone()

You should be able for each 'slave' sensor, do a lookup to find the
corresponding thermal_zone_device_ops.

quoted

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

I think try_module_get() / module_put() are adequate for this situation
as it is done on an external module and we can not rely on the exported
symbols.

I don't see how it would be possible to use these functions.
The thermal zone doesn't have the data required to use it.

Maybe a more easier way is to use the thermal_zone_device mutex.
If I get a lock before to use the thermal_zone_device ops, I have the 
guaranty that module won't be unloaded.

When a "thermal of sensor" is unloaded, it calls 
thermal_zone_of_sensor_unregister which takes a lock before
update ops.

Thanks,
Alexandre