linux-kernel - Re: [PATCH v3 8/8] dt-bindings: Add rt5033 mfd, regulator and charger

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Date:   Mon, 1 May 2023 23:16:33 +0200
From:   Jakob Hauser <jahau@...ketmail.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     Sebastian Reichel <sre@...nel.org>, Lee Jones <lee@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Beomho Seo <beomho.seo@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Stephan Gerhold <stephan@...hold.net>,
        Raymond Hackley <raymondhackley@...tonmail.com>,
        Pavel Machek <pavel@....cz>, Axel Lin <axel.lin@...ics.com>,
        ChiYuan Huang <cy_huang@...htek.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, phone-devel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH v3 8/8] dt-bindings: Add rt5033 mfd, regulator and charger

Hi Krzysztof,

On 01.05.23 19:35, Jakob Hauser wrote:
> On 01.05.23 09:21, Krzysztof Kozlowski wrote:
>> On 28/04/2023 01:30, Jakob Hauser wrote:
>>> Add device tree binding documentation for rt5033 multifunction 
>>> device, voltage
>>> regulator and battery charger.
>>>
>>> Cc: Beomho Seo <beomho.seo@...sung.com>
>>> Cc: Chanwoo Choi <cw00.choi@...sung.com>
>>> Signed-off-by: Jakob Hauser <jahau@...ketmail.com>
>>
>>
>> (...)
>>
>>> +
>>> +required:
>>> +  - monitored-battery
>>> +
>>> +additionalProperties: false
>>> +
>>> +examples:
>>> +  - |
>>> +    charger {
>>> +        compatible = "richtek,rt5033-charger";
>>> +        monitored-battery = <&battery>;
>>> +        extcon = <&muic>;
>>
>>
>> Everything up to here looked ok, but extcon is not a hardware property.
>> Please do not mix adding missing bindings for existing device with
>> adding new properties. You should use connector for the USB port.
>>

...

> And how to set up the rt5033-charger to retrieve the information of the 
> extcon/muic driver in that case?
> 

...

To add more context:
According to my understanding, the extcon subsystem provides three ways 
to get an extcon device [3]:
- by name
- by devicetree node
- by phandle

For rt5033-charger, the extcon device name can be different depending on 
the consumer device. For the node I wouldn't know how to get from the 
charger/mfd node to the extcon node, I don't see a direct relation in 
case of rt5033-charger (it's no parent node or something like that). 
Therefore I chose the third option: phandle.

In the rt5033-charger driver, the location of the 
extcon_get_edev_by_phandle() call is shown in link [4], it gets added in 
patch 6.

[3] 
https://github.com/torvalds/linux/blob/v6.3/include/linux/extcon.h#L223-L229
[4] 
https://github.com/Jakko3/linux/blob/rt5033-charger_v3/drivers/power/supply/rt5033_charger.c#L677

Kind regards,
Jakob