linux-kernel - Re: [PATCH] hwmon: (aquacomputer_d5next) Add support for temperature sensor offsets

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Date:   Sun, 23 Oct 2022 07:21:19 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Aleksa Savic <savicaleksa83@...il.com>
Cc:     linux-hwmon@...r.kernel.org, leonard.anderweit@...il.com,
        Jack Doan <me@...kdoan.com>, Jean Delvare <jdelvare@...e.com>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hwmon: (aquacomputer_d5next) Add support for temperature
 sensor offsets

On 10/23/22 06:15, Aleksa Savic wrote:
> On 2022-10-22 15:57:20 GMT+02:00, Guenter Roeck wrote:
>> Please go up to 100 columns to avoid excessive line splits.
> 
> Will fix this and other comments in v2.
> 
>> Is it really necessary to re-read the control buffer repeatedly
>> to report this value ? I don't know how costly that is, but unlike
>> the pwm value I would not expect the number to change.
> 
> Yes, aside from the driver userspace can also change settings on the
> device using hidraw and we'd end up with stale data. Reading it is
> very fast, it takes about 4ms in my testing.
> 
>> Also, is this number indeed not included in the regular reports
>> sent from the controller ?
> 
> Unfortunately, it's not. The sensor report only includes final (calculated)
> sensor readings.
> 
>> The driver doesn't distinguish between offsets in the control buffer
>> (pwm, and now temperature sensor offset) and offsets in the report buffer,
>> making it a bit difficult to determine if those are the same or not.
>> Some explanation in the driver would be nice if someone finds the time
>> to provide one. If the control buffer offsets are in a different number
>> space, they should really be marked accordingly (for example with a
>> _CTRL in the define).
> 
> I can see how it can be confusing. After this, I can send a patch to
> reorder the macros & initializations and add more comments regarding
> what is what.
> 

Please do.

Thanks,
Guenter