linux-kernel - Re: [PATCH 1/1] thermal: sysfs: avoid actual readings from sysfs

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Message-ID: <2d59de0d-5011-780a-cb6c-94e6e2b74156@linaro.org>
Date:   Fri, 30 Jun 2023 12:11:25 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Eduardo Valentin <evalenti@...nel.org>
Cc:     eduval@...zon.com, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH 1/1] thermal: sysfs: avoid actual readings from sysfs


Hi Rafael,

On 30/06/2023 10:16, Rafael J. Wysocki wrote:
> On Wed, Jun 28, 2023 at 11:10 PM Eduardo Valentin <evalenti@...nel.org> wrote:

[ ... ]

> So what about adding a new zone attribute that can be used to specify
> the preferred caching time for the temperature?
> 
> That is, if the time interval between two consecutive updates of the
> cached temperature value is less than the value of the new attribute,
> the cached temperature value will be returned by "temp".  Otherwise,
> it will cause the sensor to be read and the value obtained from it
> will be returned to user space and cached.
> 
> If the value of the new attribute is 0, everything will work as it
> does now (which will also need to be the default behavior).

I'm still not convinced about the feature.

Eduardo provided some numbers but they seem based on the characteristics 
of the I2C, not to a real use case. Eduardo?

Before adding more complexity in the thermal framework and yet another 
sysfs entry, it would be interesting to have an experiment and show the 
impact of both configurations, not from a timing point of view but with 
a temperature mitigation accuracy.

Without a real use case, this feature does make really sense IMO.


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