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

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Message-ID: <a98b6393-8d59-6824-3505-975a458c4575@linaro.org>
Date:   Sat, 1 Jul 2023 16:20:10 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Eduardo Valentin <evalenti@...nel.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>, 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 Eduardo,

On 01/07/2023 03:38, Eduardo Valentin wrote:
> Hey Daniel,
> 
> On Fri, Jun 30, 2023 at 12:11:25PM +0200, Daniel Lezcano wrote:
>>
>>
>>
>> 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?
> 
> Why I2C is not a real use case?

What I meant is "I2C is slow, ok. But what is the setup where the 
problem arises?"


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