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Subject: Re: [PATCH v7 00/11] Stop monitoring disabled devices
To:     Zhang Rui <rui.zhang@intel.com>,
        Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
        linux-pm@vger.kernel.org, linux-acpi@vger.kernel.org,
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Cc:     "Rafael J . Wysocki" <rjw@rjwysocki.net>,
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From:   Daniel Lezcano <daniel.lezcano@linaro.org>
Message-ID: <58265668-fc6d-729a-c126-0c73c2ea853b@linaro.org>
Date:   Fri, 3 Jul 2020 08:38:48 +0200
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On 03/07/2020 03:49, Zhang Rui wrote:
> On Thu, 2020-07-02 at 19:49 +0200, Daniel Lezcano wrote:

[ ... ]

>>> So the reason is that ->get_temp() is called while the mutex is
>>> held and
>>> thermal_zone_device_is_enabled() wants to take the same mutex.
>>
>> Yes, that's correct.
>>
>>> Is adding a comment to thermal_zone_device_is_enabled() to never
>>> call
>>> it while the mutex is held and adding another version of it which
>>> does
>>> not take the mutex ok?
>>
>> The thermal_zone_device_is_enabled() is only used in two places, acpi
>> and this imx driver, and given:
>>
>> 1. as soon as the mutex is released, there is no guarantee the
>> thermal
>> zone won't be changed right after, the lock is pointless, thus the
>> information also.
>>
>> 2. from a design point of view, I don't see why a driver should know
>> if
>> a thermal zone is disabled or not
>>
>> It would make sense to end with this function and do not give the
>> different drivers an opportunity to access this information.
> 
> I agree.
>>
>> Why not add change_mode for the acpi in order to enable or disable
>> the
>> events
> 
> thermal_zone_device_is_enabled() is invoked in acpi thermal driver
> because we only want to do thermal_zone_device_update() when the acpi
> thermal zone is enabled.
> 
> As thermal_zone_device_update() can handle a disabled thermal zone now,
> we can just remove the check.

Ah yes, good point!


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