linux-kernel - Re: [PATCH v5 2/4] hwmon: max31827: Add support for max31828 and max31829

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Date:   Fri, 27 Oct 2023 08:51:27 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     "Matyas, Daniel" <Daniel.Matyas@...log.com>
Cc:     Jean Delvare <jdelvare@...e.com>, Jonathan Corbet <corbet@....net>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 2/4] hwmon: max31827: Add support for max31828 and
 max31829

On 10/27/23 08:05, Matyas, Daniel wrote:
> 
> 
>> -----Original Message-----
>> From: Guenter Roeck <groeck7@...il.com> On Behalf Of Guenter Roeck
>> Sent: Friday, October 27, 2023 5:52 PM
>> To: Matyas, Daniel <Daniel.Matyas@...log.com>
>> Cc: Jean Delvare <jdelvare@...e.com>; Jonathan Corbet
>> <corbet@....net>; linux-hwmon@...r.kernel.org; linux-
>> doc@...r.kernel.org; linux-kernel@...r.kernel.org
>> Subject: Re: [PATCH v5 2/4] hwmon: max31827: Add support for
>> max31828 and max31829
>>
>> [External]
>>
>> On 10/27/23 06:00, Matyas, Daniel wrote:
>> [ ... ]
>>
>>>> I also don't understand why that would be chip specific. I don't see
>>>> anything along that line in the datasheet.
>>>>
>>>> Ah, wait ... I guess that is supposed to reflect the chip default.
>>>> I don't see why the chip default makes a difference - a well defined
>>>> default must be set either way. Again, there is no guarantee that the
>>>> chip is in its default state when the driver is loaded.
>>>
>>> The well defined default was set in v4, but I deleted it, because the
>> default value in hex for max31827 and max31828 alarm polarity, and
>> max31827 fault queue is 0x0. I had 2 #defines for these values, but you
>> said:
>>> " Since MAX31827_ALRM_POL_LOW is 0, this code doesn't really do
>> anything and just pollutes the code."
>>>
>>> So, I thought I should remove it altogether, since res is set to 0 in the
>> beginning and the default value of these chips (i.e. 0) is implicitly set.
>>>
>>>>
>>>> Also, why are the default values added in this patch and not in the
>>>> previous patch ?
>>>>
>>>
>>> In v4 these default values were set in the previous patch.
>>>
>>
>> I asked you (or meant to ask you) to stop overwriting 0 with 0 in a
>> variable. I didn't mean to ask you (if I did) to stop writing the default value
>> into the chip. Sorry if I did; if so, that was a misunderstanding.
>>
>> Guenter
> 
> Well, writing the default value into res, would just overwrite 0 with 0. Should I still do it?
> 

No, that is not correct. You don't know what is in the chip register.
It may not be the chip default.

Guenter