linux-kernel - Re: [PATCH v3 1/1] dt-bindings: hwmon: Add maxim max31790

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Message-ID: <cff4a562-2ed7-4dbc-9e2f-68ff1a601ef3@linaro.org>
Date: Tue, 13 Aug 2024 18:21:29 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Conor Dooley <conor@...nel.org>, Guenter Roeck <linux@...ck-us.net>
Cc: Chanh Nguyen <chanh@...amperecomputing.com>,
 Jean Delvare <jdelvare@...e.com>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Justin Ledford
 <justinledford@...gle.com>, devicetree@...r.kernel.org,
 linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
 OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
 Open Source Submission <patches@...erecomputing.com>,
 Phong Vo <phong@...amperecomputing.com>,
 Thang Nguyen <thang@...amperecomputing.com>,
 Quan Nguyen <quan@...amperecomputing.com>
Subject: Re: [PATCH v3 1/1] dt-bindings: hwmon: Add maxim max31790

On 13/08/2024 18:16, Conor Dooley wrote:
>>>> +examples:
>>>> +  - |
>>>> +    i2c {
>>>> +      #address-cells = <1>;
>>>> +      #size-cells = <0>;
>>>> +
>>>> +      fan-controller@21 {
>>>> +        compatible = "maxim,max31790";
>>>> +        reg = <0x21>;
>>>> +        clocks = <&sys_clk>;
>>>> +        resets = <&reset 0>;
>>>> +      };
>>>> +    };
>>>
>>> What does this example demonstrate? The one below seems useful, this one
>>> I don't quite understand - what's the point of a fan controller with no
>>> fans connected to it? What am I missing?
>>>
>>
>> Just guessing, but maybe this is supposed to reflect a system which only monitors fan
>> speeds but does not implement fan control.
> 
> Even without any control, I would expect to see fan-# child nodes, just
> no pwms property in them. Without the child nodes, how does software
> determine which fan is being monitored by which channel?

Yeah, to me this example is confusing. If device's purpose is to also
monitor, then hardware description in "description:" field should be a
bit extended.

Best regards,
Krzysztof