linux-kernel - Re: [PATCH v2 2/2] dt-bindings: google,cros-ec-keyb: add use-fn-overlay prop

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Message-ID: <aU__uxDmeUq20Mg3@google.com>
Date: Sat, 27 Dec 2025 15:48:11 +0000
From: Fabio Baltieri <fabiobaltieri@...omium.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Benson Leung <bleung@...omium.org>,
	Guenter Roeck <groeck@...omium.org>,
	Tzung-Bi Shih <tzungbi@...nel.org>, Simon Glass <sjg@...omium.org>,
	linux-input@...r.kernel.org, devicetree@...r.kernel.org,
	chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] dt-bindings: google,cros-ec-keyb: add
 use-fn-overlay prop

On Sat, Dec 27, 2025 at 01:44:26PM +0100, Krzysztof Kozlowski wrote:
> > diff --git a/Documentation/devicetree/bindings/input/google,cros-ec-keyb.yaml b/Documentation/devicetree/bindings/input/google,cros-ec-keyb.yaml
> > index fefaaf46a240..437575cdf352 100644
> > --- a/Documentation/devicetree/bindings/input/google,cros-ec-keyb.yaml
> > +++ b/Documentation/devicetree/bindings/input/google,cros-ec-keyb.yaml
> > @@ -44,6 +44,14 @@ properties:
> >        where the lower 16 bits are reserved. This property is specified only
> >        when the keyboard has a custom design for the top row keys.
> >  
> > +  google,use-fn-overlay:
> > +    description: |
> > +      Use a function key overlay. This allows defining an extra set of codes
> 
> What is a function key overlay? Overlays are DT term and therefore are
> not suitable for bindings.

Ok, guess I can rename it to `use-fn-key` or `use-fn-layer`, open to
suggestions really.

> > +      that are sent if a key is pressed while the KEY_FN is held pressed as
> > +      well. The function codes have to be defined in the linux,keymap property
> > +      with an offset of keypad,num-rows from the normal ones.
> > +    type: boolean
> > +
> >  dependencies:
> >    function-row-physmap: [ 'linux,keymap' ]
> >    google,needs-ghost-filter: [ 'linux,keymap' ]
> > @@ -132,6 +140,23 @@ examples:
> >              /* UP      LEFT    */
> >              0x070b0067 0x070c0069>;
> >      };
> > +  - |
> > +    /* With function keys */
> > +    #include <dt-bindings/input/input.h>
> > +    keyboard-controller {
> > +        compatible = "google,cros-ec-keyb";
> > +        keypad,num-rows = <8>;
> > +        keypad,num-columns = <18>;
> > +        google,use-fn-overlay;
> 
> Difference in one property does not justify new example.

Sure but when the property is set then one has to specify the extra
codes in the linux,keymap property and this examples shows how. I'll
drop it if you want me to but I think there's value in it.

> Please organize the patch documenting the compatible (DT bindings)
> before the patch using that compatible.
> See also: https://elixir.bootlin.com/linux/v6.14-rc6/source/Documentation/devicetree/bindings/submitting-patches.rst#L46

Ack, will do for v3.

Thanks for the review.
Fabio