linux-kernel - Re: [PATCH RFC 1/4] dt-bindings: input: touchscreen: Add Z2 controller bindings.

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Message-ID: <CAMT+MTRodB_+sMtoPxv-gP_+sJAwNb36XuLOGo=HvuCQq6h+gQ@mail.gmail.com>
Date:   Mon, 27 Feb 2023 21:06:28 +0100
From:   Sasha Finkelstein <fnkl.kernel@...il.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Hector Martin <marcan@...can.st>, Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        - <asahi@...ts.linux.dev>, Henrik Rydberg <rydberg@...math.org>,
        linux-arm-kernel@...ts.infradead.org, linux-input@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 1/4] dt-bindings: input: touchscreen: Add Z2
 controller bindings.

On Mon, 27 Feb 2023 at 20:51, Rob Herring <robh@...nel.org> wrote:
>
> > +properties:
> > +  compatible:
> > +    const: apple,z2-touchscreen
>
> Is 'z2' anything other than a touchscreen? If not, '-touchscreen' is
> redundant. If so, then what else is there? You should be describing
> physical devices, not just a protocol for touchscreen.
>

This is a class of touchscreen controllers that talk the z2 protocol
over spi.

> > +                    touchscreen-size-y = <640>;
> > +                    apple,z2-device-name = "MacBookPro17,1 Touch Bar";
>
> Why do we need this string? If you want a human consumed label for
> some identification, we have a property for that purpose. It's called
> 'label'. But when there is only 1 instance, I don't really see the
> point.

I want a libinput-consumed label to distinguish between devices
using this protocol. It is used both for 'normal' touchscreens, and,
as is in this example a 'touchbar', which absolutely should not be
treated as a normal touchscreen, and needs special handling in
userspace.