linux-kernel - Re: [PATCH v2 9/9] rtc: isl12022: add support for temperature sensor

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Date:   Fri, 23 Sep 2022 06:51:28 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Jean Delvare <jdelvare@...e.com>
Cc:     linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v2 9/9] rtc: isl12022: add support for temperature sensor

On 9/23/22 01:40, Rasmus Villemoes wrote:
> On 21/09/2022 16.13, Guenter Roeck wrote:
>> On 9/21/22 04:46, Rasmus Villemoes wrote:
> 
>>> +static int isl12022_hwmon_read(struct device *dev,
>>> +                   enum hwmon_sensor_types type,
>>> +                   u32 attr, int channel, long *val)
>>> +{
>>> +    if (type == hwmon_chip && attr == hwmon_chip_update_interval) {
>>> +        *val = 60000;
>>> +        return 0;
>>> +    }
>>
>> It is not the purpose of the update_interval attribute to inform the
>> user what the update interval of this chip happens to be. The purpose
>> of the attribute is to inform the chip what update interval it should use.
> 
> Well, I think it's a completely natural thing to expose a fixed and
> known update_interval as a 0444 property, and it might even be useful to
> userspace to know that there's no point reading the sensor any more
> often than that. And I didn't come up with this by myself, there's
> already at least a couple of instances of a 0444 update_interval.
> 

That doesn't make it better. It is still an abuse of the ABI.

Guenter