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

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Message-ID: <7be10595-3852-4fec-a53c-b7d8ddde84c3@linaro.org>
Date: Thu, 15 Feb 2024 09:39:18 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Stephen Boyd <swboyd@...omium.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

On 15/02/2024 01:07, Stephen Boyd wrote:
> 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?

Hm, I double checked and you're right. I thought endpoint is required
anyway by graph.yaml in dtschema, but it seems it is not.

> 
>>
>>
>>> +
>>> +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.

OK,

Best regards,
Krzysztof