linux-kernel - Re: [PATCH v6 2/8] regulator: dt-bindings: Document max8997-pmic nodes

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Date:   Mon, 4 Jan 2021 19:18:25 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Timon Baetz <timon.baetz@...tonmail.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Lee Jones <lee.jones@...aro.org>,
        Sebastian Reichel <sre@...nel.org>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-pm@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH v6 2/8] regulator: dt-bindings: Document max8997-pmic
 nodes

On Mon, Jan 04, 2021 at 01:51:56PM +0000, Mark Brown wrote:
> On Wed, Dec 30, 2020 at 08:52:07PM +0000, Timon Baetz wrote:
> 
> > +- charger: Node for configuring the charger driver.
> > +  Required properties:
> > +  - compatible: "maxim,max8997-battery"
> > +  Optional properties:
> > +  - extcon: extcon specifier for charging events
> > +  - charger-supply: regulator node for charging current
> > +
> > +- muic: Node used only by extcon consumers.
> > +  Required properties:
> > +  - compatible: "maxim,max8997-muic"
> 
> Why do these need to appear in the DT binding?  We know these features
> are there simply from knowing this is a max8997.

If you refer to children nodes, then we do not know these entirely
because the features could be disabled (pins not connected).  In such
case these subnodes can be disabled and MFD framework will not
instantiate children devices.

If you mean "the properties" like extcon or charger, then indeed it's a
good question. In theory, wires still could be routed differently, e.g.
different charging regulator used as a charger.
In practice this is highly unlikely, however such DT design allows
easier hooking up of different devices and even potential re-usage of
kernel drivers (also unlikely...).

Best regards,
Krzysztof