linux-kernel - Re: [PATCH v3 2/5] dt-bindings: input/touchscreen: Add compatible for IST3038B

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Message-Id: <CXJOLS2I8WH7.1IMVJGPUNG4VB@gimli.ms.mff.cuni.cz>
Date:   Sat, 09 Dec 2023 10:05:27 +0100
From:   "Karel Balej" <karelb@...li.ms.mff.cuni.cz>
To:     "Conor Dooley" <conor.dooley@...rochip.com>,
        "Markuss Broks" <markuss.broks@...il.com>
Cc:     "Conor Dooley" <conor@...nel.org>,
        "Dmitry Torokhov" <dmitry.torokhov@...il.com>,
        "Rob Herring" <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        "Conor Dooley" <conor+dt@...nel.org>,
        "Henrik Rydberg" <rydberg@...math.org>,
        <linux-input@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Duje Mihanović <duje.mihanovic@...le.hr>,
        <~postmarketos/upstreaming@...ts.sr.ht>,
        <phone-devel@...r.kernel.org>, "Karel Balej" <balejk@...fyz.cz>
Subject: Re: [PATCH v3 2/5] dt-bindings: input/touchscreen: Add compatible
 for IST3038B

On Mon Dec 4, 2023 at 1:52 PM CET, Conor Dooley wrote:
> On Mon, Dec 04, 2023 at 02:40:44PM +0200, Markuss Broks wrote:
> > On 12/3/23 13:20, Conor Dooley wrote:
> > > On Sat, Dec 02, 2023 at 01:48:33PM +0100, Karel Balej wrote:
> > > > From: Markuss Broks <markuss.broks@...il.com>
> > > > 
> > > > Imagis IST3038B is a variant (firmware?) of Imagis IST3038 IC,
> > > > add the compatible for it to the IST3038C bindings.
> > > This one is better, but would be well served by mentioning what
> > > specifically is different (register addresses or firmware commands?)
> > 
> > I don't think anyone knows this other than Imagis itself. I would guess it's
> > different hardware, since register addresses are indeed different, but on
> > the other hand, there is a possibility that firmware on the MCU could be
> > responding to those commands. I suppose "... IST3038B is a hardware variant
> > of ... IST3038" would be more correct.
>
> Only Imagis might know the specifics, but you (plural) have made driver
> changes so you know what is different in terms of the programming model.
> I'm just asking for you to mention how the programming model varies in
> the commit message. Otherwise I can't know whether you should have added
> a fallback compatible, without going and reading your driver change. The
> commit message for the bindings should stand on its own merit in that
> regard.
> "Variant" alone does not suffice, as many variants of devices have a
> compatible programming model, be that for a subset of features or
> complete compatibility.
>
> > The reason why I think it could be firmware-defined is because we have a lot
> > of variants (30xxA, 30xxB, 30xxC, plain 30xx), and the numbers usually mean
> > feature level/completeness, e.g. some don't support the touch pressure or
> > touchkeys, and we don't know what A/B/C/none means.
>
> Ultimately whether it is due to firmware or the hardware isn't
> particular important, just mention what is incompatibly different.

I propose to update the commit description as such:

	Imagis IST3038B is a variant (firmware?) of Imagis IST3038 IC
	differing from IST3038C in its register interface. Add the
	compatible for it to the IST3038C bindings.

>
> Cheers,
> Conor.
>
>
> > > > Signed-off-by: Markuss Broks <markuss.broks@...il.com>
> > > > Signed-off-by: Karel Balej <balejk@...fyz.cz>
> > > > ---
> > > >   .../devicetree/bindings/input/touchscreen/imagis,ist3038c.yaml   | 1 +
> > > >   1 file changed, 1 insertion(+)
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/input/touchscreen/imagis,ist3038c.yaml b/Documentation/devicetree/bindings/input/touchscreen/imagis,ist3038c.yaml
> > > > index 0d6b033fd5fb..b5372c4eae56 100644
> > > > --- a/Documentation/devicetree/bindings/input/touchscreen/imagis,ist3038c.yaml
> > > > +++ b/Documentation/devicetree/bindings/input/touchscreen/imagis,ist3038c.yaml
> > > > @@ -18,6 +18,7 @@ properties:
> > > >     compatible:
> > > >       enum:
> > > > +      - imagis,ist3038b
> > > >         - imagis,ist3038c
> > > >     reg:
> > > > -- 
> > > > 2.43.0
> > > > 
> > - Markuss

Kind regards,
K. B.