linux-kernel - Re: [PATCH RFC 0/8] thermal: core: Allow setting the parent device of thermal zone/cooling devices

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Message-ID: <CAJZ5v0gZ7+i+irhaq2jQpTt++HuVRjqz8==Ov9VmQ9Q1J1TM0w@mail.gmail.com>
Date: Fri, 14 Nov 2025 13:13:12 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Armin Wolf <W_Armin@....de>
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Subject: Re: [PATCH RFC 0/8] thermal: core: Allow setting the parent device of
 thermal zone/cooling devices

On Fri, Nov 14, 2025 at 4:24 AM Armin Wolf <W_Armin@....de> wrote:
>
> Drivers registering thermal zone/cooling devices are currently unable
> to tell the thermal core what parent device the new thermal zone/
> cooling device should have, potentially causing issues with suspend
> ordering

Do you have any examples of this?

> and making it impossible for user space appications to
> associate a given thermal zone device with its parent device.
>
> This patch series aims to fix this issue by extending the functions
> used to register thermal zone/cooling devices to also accept a parent
> device pointer. The first six patches convert all functions used for
> registering cooling devices, while the functions used for registering
> thermal zone devices are converted by the remaining two patches.
>
> I tested this series on various devices containing (among others):
> - ACPI thermal zones
> - ACPI processor devices
> - PCIe cooling devices
> - Intel Wifi card
> - Intel powerclamp
> - Intel TCC cooling
>
> I also compile-tested the remaining affected drivers, however i would
> still be happy if the relevant maintainers (especially those of the
> mellanox ethernet switch driver) could take a quick glance at the
> code and verify that i am using the correct device as the parent
> device.
>
> This work is also necessary for extending the ACPI thermal zone driver
> to support the _TZD ACPI object in the future.

Can you please elaborate a bit here?

_TZD is a list of devices that belong to the given thermal zone, so
how is it connected to the thermal zone parent?

> Signed-off-by: Armin Wolf <W_Armin@....de>
> ---
> Armin Wolf (8):
>       thermal: core: Allow setting the parent device of cooling devices
>       thermal: core: Set parent device in thermal_of_cooling_device_register()
>       ACPI: processor: Stop creating "device" sysfs link
>       ACPI: fan: Stop creating "device" sysfs link
>       ACPI: video: Stop creating "device" sysfs link
>       thermal: core: Set parent device in thermal_cooling_device_register()
>       ACPI: thermal: Stop creating "device" sysfs link
>       thermal: core: Allow setting the parent device of thermal zone devices

I can only see the first three patches in the series ATM as per

https://lore.kernel.org/linux-pm/20251114-thermal-device-v1-0-d8b442aae38b@gmx.de/T/#r605b23f2e27e751d8406e7949dad6f5b5b112067