linux-kernel - Re: [PATCH v2] ACPI: thermal: Support for linking devices associated with the thermal zone

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Message-ID: <ee3f6294-dc62-11d2-9467-53fd9241a922@huawei.com>
Date: Mon, 18 Nov 2024 09:29:42 +0800
From: "lihuisong (C)" <lihuisong@...wei.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
CC: <linux-pm@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <rui.zhang@...el.com>,
	<liuyonglong@...wei.com>, <zhanjie9@...ilicon.com>, <zhenglifeng1@...wei.com>
Subject: Re: [PATCH v2] ACPI: thermal: Support for linking devices associated
 with the thermal zone


在 2024/11/14 19:53, Rafael J. Wysocki 写道:
> Hi,
>
> On Thu, Nov 14, 2024 at 9:37 AM lihuisong (C) <lihuisong@...wei.com> wrote:
>> Hi Rafael,
>>
>> 在 2024/11/13 17:26, Rafael J. Wysocki 写道:
>>> On Wed, Nov 13, 2024 at 10:07 AM Huisong Li <lihuisong@...wei.com> wrote:
>>>> There are many 'cdevX' files which link cooling devices under
>>>> '/sys/class/thermal/thermal_zoneX/'. These devices contain active cooling
>>>> devices and passive cooling devices. And user cann't directly know which
>>>> devices temperature is represented by the thermal zone.
>>>>
>>>> However, ACPI spec provides a '_TZD' object which evaluates to a package
>>>> of device names. Each name corresponds to a device in the ACPI namespace
>>>> that is associated with the thermal zone. The temperature reported by the
>>>> thermal zone is roughly correspondent to that of each of the devices.
>>>>
>>>> User can get all devices a thermal zone measured by the 'measures'
>>>> directory under the thermal zone device.
>>> Well, that's kind of clear, but what exactly is the use case?  Why
>>> does the user need to know that?
>> IMO, this makes thermal zone information more friendly.
>> For instance, user can directly know the temperature of CPUs or other
>> devices is roughly represented by which thermal zone.
>> This may offer the convenience for further usersapce application.
>>
>> BTW, the '_TZD' method is similar to the '_PMD' in acpi power meter.
>> Since ACPI spec provides them, they should also have a role in their
>> existence.
> So there is no specific use case, but it is possible that somebody may
> want to use this information, IIUC.
>
> Well, let's defer making kernel changes until there is a user
> wanting/needing this information.  Then we'll decide how to expose it.
>
> For one, I'm not convinced that exposing it under the ACPI
> representation of a thermal zone is going to be really useful.
All right. Thanks for your review.
>
> .