linux-kernel - Re: [PATCH 18/22] dt-bindings: chrome: Add binding for ChromeOS Pogo pin connector

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Date: Wed, 14 Feb 2024 16:07:43 -0800
From: Stephen Boyd <swboyd@...omium.org>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, chrome-platform@...ts.linux.dev
Cc: linux-kernel@...r.kernel.org, patches@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, Douglas Anderson <dianders@...omium.org>, 
	Pin-yen Lin <treapking@...omium.org>, Rob Herring <robh+dt@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Benson Leung <bleung@...omium.org>, Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH 18/22] dt-bindings: chrome: Add binding for ChromeOS Pogo
 pin connector

Quoting Krzysztof Kozlowski (2024-02-11 05:39:36)
> On 10/02/2024 08:09, Stephen Boyd wrote:
> > diff --git a/Documentation/devicetree/bindings/chrome/google,pogo-pin-connector.yaml b/Documentation/devicetree/bindings/chrome/google,pogo-pin-connector.yaml
> > new file mode 100644
> > index 000000000000..5ba68fd95fcd
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/chrome/google,pogo-pin-connector.yaml
> > @@ -0,0 +1,61 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
[...]
>
> > +properties:
> > +  compatible:
> > +    const: google,pogo-pin-connector
> > +
> > +  "#address-cells":
> > +    const: 1
> > +
> > +  "#size-cells":
> > +    const: 0
> > +
> > +  port:
> > +    $ref: /schemas/graph.yaml#/properties/port
> > +    description: Connection to USB2 port providing USB signals
> > +    required:
> > +      - endpoint
>
> Drop required.

Why? I'd like to make it so you can't have the node defined without
connecting it up to the rest of the system. Is that bad?

>
>
> > +
> > +patternProperties:
> > +  "^keyboard@[0-9a-f]{1,2}$":
> > +    description: The detachable keyboard
>
> If this is detachable why do you define it in DT? Only hard-wired USB
> devices, which need some sort of special handling. are described in DT.

>From the commit text:

 We expect to find a keyboard on the other side of this connector with a
 specific vid/pid, so describe that as a child device at the port of the
 usb device connected upstream.

ChromeOS userspace is checking that the connected device downstream of
this port has the expected vid/pid to quickly rule out USB keyboards
that aren't the detachable keyboard. I wanted to express this in DT so
that it didn't live in ChromeOS userspace forever.