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

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Message-ID: <CAA8EJpoJzGWM_1DDY1AfB35qFz+58LVhO+L7t5fKC9HoUsR0sg@mail.gmail.com>
Date:   Thu, 16 Nov 2023 22:48:09 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Rob Herring <robh@...nel.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 Thu, 16 Nov 2023 at 20:38, Rob Herring <robh@...nel.org> wrote:
>
> 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.

I had an idea of defining a schema piece that can later be referenced
from any other place. If you think this is an overkill, I can drop
them.

>
> > +  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?

Ack, I'll expand it in v3

>
> 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.

Indeed it might be better to enumerate them via string enumeration.

>
>
> > +        $ref: "#/$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
> >



-- 
With best wishes
Dmitry