linux-kernel - Re: [PATCH v2 1/2] dt-bindings: iio: pressure: add honeywell,hsc030

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Message-ID: <20231125192126.55cda541@jic23-huawei>
Date:   Sat, 25 Nov 2023 19:21:26 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Petre Rodan <petre.rodan@...dimension.ro>
Cc:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org, Conor Dooley <conor+dt@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH v2 1/2] dt-bindings: iio: pressure: add honeywell,hsc030

On Mon, 20 Nov 2023 20:25:08 +0200
Petre Rodan <petre.rodan@...dimension.ro> wrote:

> Hello!
> 
> On Mon, Nov 20, 2023 at 05:39:29PM +0000, Jonathan Cameron wrote:
> > On Mon, 20 Nov 2023 16:40:51 +0200
> > Petre Rodan <petre.rodan@...dimension.ro> wrote:
> >   
> > > Hello!
> > > 
> > > On Mon, Nov 20, 2023 at 03:04:07PM +0100, Krzysztof Kozlowski wrote:  
> > > > On 20/11/2023 14:42, Petre Rodan wrote:
> > > >     
> > > > >>> +properties:
> > > > >>> +  compatible:
> > > > >>> +    enum:
> > > > >>> +      - honeywell,hsc    
> > > > >>
> > > > >> Way too generic    
> > > > > 
> > > > > I'm new to this, please excuse my ignorance.
> > > > > my driver covers all Honeywell pressure sensors under the "TruStability board mount HSC/SSC" moniker.    
> > > > 
> > > > We talk here about bindings, not driver. For the driver you can use
> > > > whatever name is approved by reviewers of your driver.
> > > >     
> > > > > that is why my intention was to provide a rather generic name for the driver itself.
> > > > > are you afraid that they will come up with a different device that they will call "hsc" in the future?
> > > > > in this case honeywell,trustability-hsc would be fine?
> > > > > 
> > > > > as I see you prefer to target a particular chip, but I am a bit afraid that the end-user will be confused by needing to set up something like
> > > > > 
> > > > > pressure@28 {
> > > > > 	compatible = "honeywell,hsc030pa";    
> > > > 
> > > > The compatible should be specific, thus for example match exact model
> > > > number.    
> > > 
> > > there are an infinite number of combinations of 4 transfer functions and 118 ranges + one custom range, so providing an array with all specific chips that could end up as compatible is out of the question.
> > > I was aiming at providing a generic name for the binding and get the transfer function and the pressure range as required parameters.
> > >   
> > > > If you can guarantee that all devices from given family are the same in
> > > > respect of programming model and hardware requirements (e.g. supplies),
> > > > then you could go with family name. However such guarantees are rarely
> > > > given.    
> > > 
> > > I see your point.
> > >   
> > > > Therefore for mprls0025pa I agreed for using one specific model
> > > > for entire family.
> > > > 
> > > > https://lore.kernel.org/all/d577bc44-780f-f25d-29c6-ed1d353b540c@linaro.org/
> > > > 
> > > >     
> > > > > 	reg = <0x28>;
> > > > > 	honeywell,transfer-function = <0>;
> > > > > 	honeywell,pressure-range = "250MD";
> > > > > };
> > > > > 
> > > > > ie. specifying "hsc030pa" as driver while his chip is not in the 030PA range, but 250MD.
> > > > > 
> > > > > so do you prefer
> > > > >  honeywell,trustability-hsc  OR
> > > > >  honeywell,hsc030pa    
> > > > 
> > > > I think the latter, just like we did for mprls0025pa. How many devices
> > > > do you have there?    
> > > 
> > > both hsc and ssc have 118 ranges, 4 transfer functions and both can be requested from the manufacturer with custom measurement ranges.
> > > 
> > > ok,I will rename hsc->hsc030pa in the code as you requested.  
> > 
> > Where does pa come from?   
> 
> honeywell,hsc030pa was provided as an equivalent to honeywell,mprls0025pa (which is already in the repo).
> 
> '030PA' and '0025PA' define the pressure range (0-30, 0-25), the unit of measure (Psi) and the measurement type (Absolute) for a particular chip in the honeywell catalog. (please ignore the psi part, we convert everything to pascals).
> but both my driver and Andreas Klinger's mprls0025pa actually provide a generic abstraction layer for entire series of sensors.

ah ok. That's fine then - searching the datasheet I found didn't include that particular
string, so I was rather confused.

I'm fine with specific now you've explained where it came from!

Jonathan

> 
> > If we are going generic, feels like trustability-ssc etc are more representative
> > and matches the datasheet cover page.  
> 
> Krzysztof voted for non-generic, honeywell,mprls0025pa is already set up non-generic, my intent was to go generic.
> 
> I'll rewrite the code to whatever you guys feel is best.
> 
> peter
> 
>