netdev - Re: [PATCH v4 04/11] thermal: Store device mode in struct thermal_zone

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Message-ID: <a0c0310f-9870-47be-4ca3-c07e41c380fc@collabora.com>
Date:   Fri, 29 May 2020 19:21:50 +0200
From:   Andrzej Pietrasiewicz <andrzej.p@...labora.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     linux-pm@...r.kernel.org, linux-acpi@...r.kernel.org,
        netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
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        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Heiko Stuebner <heiko@...ech.de>,
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        Vishal Kulkarni <vishal@...lsio.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
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        Chunyan Zhang <zhang.lyra@...il.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
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        Andy Shevchenko <andy@...radead.org>
Subject: Re: [PATCH v4 04/11] thermal: Store device mode in struct
 thermal_zone_device

Hi again,

W dniu 29.05.2020 o 18:08, Andrzej Pietrasiewicz pisze:
> Hi Guenter,
> 
> W dniu 29.05.2020 o 17:42, Guenter Roeck pisze:
>> On Thu, May 28, 2020 at 09:20:44PM +0200, Andrzej Pietrasiewicz wrote:
>>> Prepare for eliminating get_mode().
>>>
>> Might be worthwhile to explain (not only in the subject) what you are
>> doing here.
>>
>>> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@...labora.com>
>>> ---
>>>   drivers/acpi/thermal.c                        | 18 ++++++----------
>>>   .../ethernet/mellanox/mlxsw/core_thermal.c    | 21 +++++++------------
>>>   drivers/platform/x86/acerhdf.c                | 15 ++++++-------
>>>   drivers/thermal/da9062-thermal.c              |  6 ++----
>>>   drivers/thermal/imx_thermal.c                 | 17 +++++++--------
>>>   .../intel/int340x_thermal/int3400_thermal.c   | 12 +++--------
>>>   .../thermal/intel/intel_quark_dts_thermal.c   | 16 +++++++-------
>>>   drivers/thermal/thermal_of.c                  | 10 +++------
>>
>> After this patch is applied on top of the thermal 'testing' branch,
>> there are still local instances of thermal_device_mode in
>>     drivers/thermal/st/stm_thermal.c
>>     drivers/thermal/ti-soc-thermal/ti-thermal-common.c
>>
>> If there is a reason not to replace those, it might make sense to explain
>> it here.
>>
> 
> My understanding is that these two are sensor devices which are "plugged"
> into their "parent" thermal zone device. The latter is the "proper" tzd.
> They both use thermal_zone_of_device_ops instead of thermal_zone_device_ops.
> The former doesn't even have get_mode(). The thermal core, when it calls
> get_mode(), operates on the "parent" thermal zone devices.
> 
> Consequently, the drivers you mention use their "mode" members for
> their private purpose, not for the purpose of storing the "parent"
> thermal zone device mode.
> 

Let me also say it differently.

Both drivers which you mention use devm_thermal_zone_of_sensor_register().
It calls thermal_zone_of_sensor_register(), which "will search the list of
thermal zones described in device tree and look for the zone that refer to
the sensor device pointed by @dev->of_node as temperature providers. For
the zone pointing to the sensor node, the sensor will be added to the DT
thermal zone device." When a match is found thermal_zone_of_add_sensor()
is invoked, which (using thermal_zone_get_zone_by_name()) iterates over
all registered thermal_zone_devices. The one eventually found will be
returned and propagated to the original caller of
devm_thermal_zone_of_sensor_register(). The state of this returned
device is managed elsewhere (in that device's struct tzd). The "mode"
member you are referring to is thus unrelated.

Regards,

Andrzej