linux-kernel - Re: [PATCH 1/3] thermal: core: Add indication for userspace usage

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Date:   Wed, 9 Dec 2020 10:30:22 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Zhang Rui <rui.zhang@...el.com>, amitk@...nel.org,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] thermal: core: Add indication for userspace usage

On 07/12/2020 06:36, Kai-Heng Feng wrote:
> 
> 
>> On Dec 1, 2020, at 02:39, Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com> wrote:
>>
>> On Tue, 2020-12-01 at 02:22 +0800, Kai-Heng Feng wrote:
>>>> On Dec 1, 2020, at 02:13, Srinivas Pandruvada <
>>>> srinivas.pandruvada@...ux.intel.com> wrote:
>>>
>>> [snipped] 
>>>
>>>>>> What about creating an new callback
>>>>>>
>>>>>> enum thermal_trip_status {
>>>>>> 	THERMAL_TRIP_DISABLED = 0,
>>>>>> 	THERMAL_TRIP_ENABLED,
>>>>>> };
>>>>>>
>>>>>> int get_trip_status(struct thermal_zone_device *, int trip,
>>>>>> enum
>>>>>> thermal_trip_status *state);
>>>>>>
>>>>>> Then in 
>>>>>> static void handle_thermal_trip(struct thermal_zone_device *tz,
>>>>>> int
>>>>>> trip)
>>>>>> {
>>>>>>
>>>>>> /* before tz->ops->get_trip_temp(tz, trip, &trip_temp); */
>>>>>> if (tz->ops->get_trip_status) {
>>>>>> 	enum thermal_trip_status *status;
>>>>>>
>>>>>> 	if (!tz->ops->get_trip_status(tz, trip, &status)) {
>>>>>> 		if (status == THERMAL_TRIP_DISABLED)
>>>>>> 			return;	
>>>>>> 	}
>>>>>> }
>>>>>> ...
>>>>>> ...
>>>>>>
>>>>>> }
>>>>>>
>>>>>>
>>>>>> This callback will help the cases:
>>>>>> - Allows drivers to selectively disable certain trips during
>>>>>> init
>>>>>> state
>>>>>> or system resume where there can be spikes or always. int340x
>>>>>> drivers
>>>>>> can disable always.
>>>>>
>>>>> This sounds really great. This is indeed can happen on system
>>>>> resume,
>>>>> before userspace process thaw.
>>>>>
>>>>>> - Still give options for drivers to handle critical trip even
>>>>>> if
>>>>>> they
>>>>>> are bound to user space governors. User space process may be
>>>>>> dead,
>>>>>> so
>>>>>> still allow kernel to process graceful shutdown
>>>>>
>>>>> To make the scenario happen, do we need a new sysfs to let
>>>>> usespace
>>>>> enable it with THERMAL_TRIP_ENABLED?
>>>> This should be drivers call not user space.
>>>
>>> Understood. So after thermal_zone_device_register(), the driver can
>>> decide to what to return on get_trip_temp().
>> get_trip_status()
>>
>>> Let me work on a new patch if there's no other concern.
>> Better to wait for confirmation from Daniel and others.
> 
> Daniel,
> 
> Do you like Srinivas' proposed solution?
> 
> I hope we can find a solution in upstream kernel soon.

(just trying to figure out the full context)

If the device is enumerated outside of a thermal zone, the sensor should
not register in the thermal zone no ?



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