linux-kernel - Re: [PATCH v2 1/3] dt-bindings: connector: usb: add altmodes description

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Date:   Thu, 16 Nov 2023 12:38:02 -0600
From:   Rob Herring <robh@...nel.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Mark Gross <markgross@...nel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH v2 1/3] dt-bindings: connector: usb: add altmodes
 description

On Tue, Nov 14, 2023 at 12:13:27AM +0200, Dmitry Baryshkov wrote:
> Add description of the USB-C AltModes supported on the particular USB-C
> connector. This is required for devices like Qualcomm Robotics RB5,
> which have no other way to express alternative modes supported by the
> hardware platform.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> ---
>  .../bindings/connector/usb-connector.yaml     | 36 +++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/connector/usb-connector.yaml b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> index 7c8a3e8430d3..1bd51b86906f 100644
> --- a/Documentation/devicetree/bindings/connector/usb-connector.yaml
> +++ b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> @@ -14,6 +14,31 @@ description:
>    of a USB interface controller or a separate node when it is attached to both
>    MUX and USB interface controller.
>  
> +$defs:

I fail to see why we need to use $defs here.

> +  altmode-desc:
> +    type: object
> +    description:
> +      A single USB-C Alternative Mode as supported by the USB-C connector logic.
> +    properties:
> +      svid:
> +        $ref: /schemas/types.yaml#/definitions/uint16
> +        description: Unique value assigned by USB-IF to the Vendor / AltMode.
> +      vdo:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        description: VDO returned by Discover Modes USB PD command.

What's VDO?

These names are a bit short. Types for property names are global 
(mostly). Though this patch doesn't make it clear these were already in 
use.

> +
> +  altmodes-list:
> +    type: object
> +    description: List of Alternative Modes supported by the schematics on the
> +      particular device. This is only necessary if there are no other means to
> +      discover supported alternative modes (e.g. through the UCSI firmware
> +      interface).
> +
> +    patternProperties:
> +      "^[a-z][a-z0-9]*$":

Are there standard id's and names? Should we define some so we don't get 
'dp', 'displayport', etc.


> +        $ref: "#/$defs/altmode-desc"
> +        unevaluatedProperties: false
> +
>  properties:
>    compatible:
>      oneOf:
> @@ -171,6 +196,10 @@ properties:
>        offer the power, Capability Mismatch is set. Required for power sink and
>        power dual role.
>  
> +  altmodes:
> +    $ref: "#/$defs/altmodes-list"
> +    unevaluatedProperties: false
> +
>    port:
>      $ref: /schemas/graph.yaml#/properties/port
>      description: OF graph bindings modeling a data bus to the connector, e.g.
> @@ -289,6 +318,13 @@ examples:
>              compatible = "usb-c-connector";
>              label = "USB-C";
>  
> +            altmodes {
> +                displayport {
> +                    svid = /bits/ 16 <0xff01>;
> +                    vdo = <0x00001c46>;
> +                };
> +            };
> +
>              ports {
>                  #address-cells = <1>;
>                  #size-cells = <0>;
> -- 
> 2.42.0
>