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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAJZ5v0h7vrqMquOgCAiBG1Pe7=mF4XGug6-CUT7=Y5daRDRt6w@mail.gmail.com>
Date: Fri, 14 Nov 2025 21:10:13 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Armin Wolf <w_armin@....de>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>, 
	Lukasz Luba <lukasz.luba@....com>, Hans de Goede <hansg@...nel.org>, 
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH RFC 0/8] thermal: core: Allow setting the parent device of
 thermal zone/cooling devices

CC list trimmed and I'd rather not use such an extensive one if I were you.

On Fri, Nov 14, 2025 at 1:13 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> 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?

Especially for thermal zones.

> > 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

This will kind of break things because user space may rely on those, may it not?

> >       thermal: core: Allow setting the parent device of thermal zone devices

For this last change, you need to define what it means for a thermal
zone to have a parent device.  In particular, in what way would a
thermal zone depend on its parent?

> 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

That's probably because of the excessive CC list.