linux-kernel - Re: [PATCH 1/3] dt-bindings: iio: pressure: Support Honeywell mpr sensors

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Message-ID: <ZC8oepuINTaMqN9M@arbad>
Date:   Thu, 6 Apr 2023 22:15:54 +0200
From:   Andreas Klinger <ak@...klinger.de>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Angel Iglesias <ang.iglesiasg@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: iio: pressure: Support Honeywell mpr
 sensors

Hi,

thanks to Krzysztof, Lars-Peter and Jonathan for the review and suggestions. I
have one thing to clarify. See below.

Jonathan Cameron <jic23@...nel.org> schrieb am Sa, 01. Apr 16:27:
> On Sat, 1 Apr 2023 11:42:15 +0200
> Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:
> 
> > On 01/04/2023 11:09, Andreas Klinger wrote:
[...]
> > > +  honeywell,pmin:
> > > +    description:
> > > +      Minimum pressure value the sensor can measure in pascal.  
> > 
> > Use standard unit suffix:
> > https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/property-units.yaml
> > 
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +
> > > +  honeywell,pmax:
> > > +    description:
> > > +      Maximum pressure value the sensor can measure in pascal.
> > > +    $ref: /schemas/types.yaml#/definitions/uint32  
> > 
> > Same.
> > 
> > Why these values are suitable for DT? Does it depend on type of sensor
> > (thus it is implied from compatible) or on system setup?
> 
> I think we'll end up with a lot of compatibles, but that's still better
> than free form description.  May still need these as well though given
> the datasheet helpfully adds a foot note.
> 
> 1. Custom pressure ranges are available.
> 
> Might not be worth including all the details though but unhelpfully the
> bits we care about are after details like is the gel food grade or the port long.
> Definitely can ignore the encoding of i2c address / spi in the last few bits but
> may need the transfer function.
> 
> 
> mpr-0025GA-A maybe as a form?

Just to clarify: There are 32 different pressure ranges and 3 transfer functions
which means we'll end up with 96 compatibles and 96 I2C ids.

Would it be an option to have only one dt compatible and to add the pressure
range as dt property?
e. g.: honeywell,range = "0025PA";

But because of "Custom pressure ranges" we still need the DT properties. In this
case there's another "mpr-custom" compatible, right?

Andreas