linux-kernel - Re: [PATCH 1/3] iio: adc: Convert the QCOM SPMI ADC bindings to .yaml format

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Date:   Tue, 14 Apr 2020 14:39:13 +0530
From:   Amit Kucheria <amit.kucheria@...aro.org>
To:     Jishnu Prakash <jprakash@...eaurora.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Jonathan.Cameron@...wei.com,
        Siddartha Mohanadoss <smohanad@...eaurora.org>,
        kgunda@...eaurora.org, aghayal@...eaurora.org,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Andy Gross <andy.gross@...aro.org>,
        "open list:IIO SUBSYSTEM AND DRIVERS" <linux-iio@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCH 1/3] iio: adc: Convert the QCOM SPMI ADC bindings to .yaml format

On Mon, Apr 6, 2020 at 5:15 PM Jishnu Prakash <jprakash@...eaurora.org> wrote:
>
> Hi Amit,
>
> On 4/3/2020 5:34 PM, Amit Kucheria wrote:
> >
> >> +required:
> >> +  - compatible
> >> +  - reg
> >> +  - '#address-cells'
> >> +  - '#size-cells'
> >> +  - '#io-channel-cells'
> >> +
> >> +patternProperties:
> >> +  "^[a-z0-9-_@]$":
> >> +    type: object
> >> +    description: |
> >> +      Represents the external channels which are connected to the ADC.
> >> +      For compatible property "qcom,spmi-vadc" following channels, also known as
> >> +      reference point channels, are used for result calibration and their channel
> >> +      configuration nodes should be defined:
> >> +      VADC_REF_625MV and/or VADC_SPARE1(based on PMIC version) VADC_REF_1250MV,
> >> +      VADC_GND_REF and VADC_VDD_VADC.
> > Instead of this note for "qcom,spmi-vadc", you can enforce this
> > through checks in YAML grammar.
> >
> > A simple example can be found in
> > Documentation/devicetree/bindings/thermal/qcom-tsens.yaml. Look for
> > the if, then, else clause which determines how many interrupts need to
> > be defined.
>
> I have gone through tsens and other examples, but I'm not able to get a
> way to apply this kind of constraint, on what child nodes should be present.
>
> In this case, the constraint would have to be that for compatible
> property "qcom,spmi-vadc", there should be at least four child nodes and
> those four should have their "reg" property fixed to the channel values
> mentioned above. I can see how to apply constraints on a single property
> like interrupts in tsens, but I'm not sure if there is a way to specify
> a lower limit to the number of child nodes or something like "there
> should be at least one child node with value 0x9 for its "reg"
> property". I could not find any examples with constraints placed on
> number of occurrences of a child node.
>
> Can you please share an example of such a constraint if you are aware of
> any or suggest some way by which this kind of constraint can be specified?

Hi Jishnu,

I misread that particular property. I don't think it is possible to
specify child nodes w/o splitting this binding into two, I think.
Please go ahead with the rest of changes. I'll keep digging to see if
this is possible.

Regards,
Amit