linux-kernel - Re: [PATCH v2] dt-bindings: Convert usb-connector to YAML format.

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Date:   Thu, 5 Mar 2020 14:08:58 -0800
From:   Prashant Malani <pmalani@...omium.org>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Stephen Boyd <swboyd@...omium.org>, devicetree@...r.kernel.org,
        Benson Leung <bleung@...omium.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Linux USB List <linux-usb@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: Re: [PATCH v2] dt-bindings: Convert usb-connector to YAML format.

Thanks Rob for reviewing this patch. Kindly see my responses inline.

Best regards,

-Prashant

On Thu, Mar 05, 2020 at 03:40:18PM -0600, Rob Herring wrote:
> On Thu, Mar 5, 2020 at 3:20 PM Stephen Boyd <swboyd@...omium.org> wrote:
> >
> > Quoting Prashant Malani (2020-03-04 19:01:30)
> > > diff --git a/Documentation/devicetree/bindings/connector/usb-connector.yaml b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> > > new file mode 100644
> > > index 0000000000000..b386e2880405c
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> > > @@ -0,0 +1,203 @@
> > > +# SPDX-License-Identifier: GPL-2.0-only
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/connector/usb-connector.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: USB Connector
> > > +
> > > +maintainers:
> > > +  - linux-usb@...r.kernel.org
> > > +
> > > +description:
> > > +  A USB connector node represents a physical USB connector. It should be a child
> > > +  of a USB interface controller.
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - usb-a-connector
> > > +      - usb-b-connector
> > > +      - usb-c-connector
> > > +
> > > +  label:
> > > +    description: Symbolic name for the connector.
> > > +
> > > +  type:
> > > +    description: Size of the connector, should be specified in case of USB-A,
> > > +      USB-B non-fullsize connectors.
> >
> > Maybe "should be specified in case of non-fullsize 'usb-a-connector' or
> > 'usb-b-connector' compatible connectors"?
> >
> > > +    $ref: /schemas/types.yaml#definitions/string
> > > +    enum:
> > > +      - mini
> > > +      - micro
> > > +
> > > +  self-powered:
> > > +    description: Set this property if the USB device has its own power source.
> > > +    type: boolean
> > > +
> > > +  # The following are optional properties for "usb-b-connector".
> > > +  id-gpios:
> > > +    description: An input gpio for USB ID pin.
> > > +    maxItems: 1
> > > +
> > > +  vbus-gpios:
> > > +    description: An input gpio for USB VBus pin, used to detect presence of
> > > +      VBUS 5V. See gpio/gpio.txt.
> >
> > Can this be written as bindings/gpio/gpio.txt?
> 
> Or just drop the reference so we don't have to fix it later.

Dropped the reference.
> 
> > > +    maxItems: 1
> > > +
> > > +  vbus-supply:
> > > +    description: A phandle to the regulator for USB VBUS if needed when host
> > > +      mode or dual role mode is supported.
> > > +      Particularly, if use an output GPIO to control a VBUS regulator, should
> > > +      model it as a regulator. See regulator/fixed-regulator.yaml
> >
> > And bindings/regulator/fixed-regulator.yaml? The idea is to
> > disambiguate from kernel Documentation/ directory.
> >
> > > +
> > > +  # The following are optional properties for "usb-c-connector".
> >
> > Is there a way to constrain the binding so that this can't be put in a
> > connector that doesn't have the usb-c-connector compatible string?
> 
> Yes, with if/then and setting excluded properties to 'false'.
> Personally, I don't think it is worth the messiness. I'm not too
> worried if folks put in properties that are going to be ignored.

Leaving this as is for now, based on the above comment.
> 
> Rob
> 
> > > +  power-role:
> > > +    description: Determines the power role that the Type C connector will
> > > +      support. "dual" refers to Dual Role Port (DRP).
> > > +    allOf:
> > > +      - $ref: /schemas/types.yaml#definitions/string
> > > +    enum:
> > > +      - source
> > > +      - sink
> > > +      - dual
> > > +
> > > +  try-power-role:
> > > +    description: Preferred power role.
> > > +    allOf:
> > > +      - $ref: /schemas/types.yaml#definitions/string
> > > +    enum:
> > > +     - source
> > > +     - sink
> > > +     - dual
> > > +
> > > +  data-role:
> > > +    description: Data role if Type C connector supports USB data. "dual" refers
> > > +      Dual Role Device (DRD).
> > > +    allOf:
> > > +      - $ref: /schemas/types.yaml#definitions/string
> > > +    enum:
> > > +      - host
> > > +      - device
> > > +      - dual
> >
> > Is there a way to maintain a description for each possible string
> > property? Then we could move the last sentence in the description above
> > to be attached to '- dual' here.
> >
> > > +
> > > +  # The following are optional properties for "usb-c-connector" with power
> > > +  # delivery support.
> > > +  source-pdos:
> > > +    description: An array of u32 with each entry providing supported power
> > > +      source data object(PDO), the detailed bit definitions of PDO can be found
> > > +      in "Universal Serial Bus Power Delivery Specification" chapter 6.4.1.2
> > > +      Source_Capabilities Message, the order of each entry(PDO) should follow
> > > +      the PD spec chapter 6.4.1. Required for power source and power dual role.
> > > +      User can specify the source PDO array via PDO_FIXED/BATT/VAR/PPS_APDO()
> > > +      defined in dt-bindings/usb/pd.h.
> > > +    minItems: 1
> > > +    maxItems: 7
> > > +    allOf:
> > > +      - $ref: /schemas/types.yaml#/definitions/uint32-array
> > > +
> > > +  sink-pdos:
> > > +    description: An array of u32 with each entry providing supported power sink
> > > +      data object(PDO), the detailed bit definitions of PDO can be found in
> > > +      "Universal Serial Bus Power Delivery Specification" chapter 6.4.1.3
> > > +      Sink Capabilities Message, the order of each entry(PDO) should follow the
> > > +      PD spec chapter 6.4.1. Required for power sink and power dual role. User
> > > +      can specify the sink PDO array via PDO_FIXED/BATT/VAR/PPS_APDO() defined
> > > +      in dt-bindings/usb/pd.h.
> > > +    minItems: 1
> > > +    maxItems: 7
> > > +    allOf:
> > > +      - $ref: /schemas/types.yaml#/definitions/uint32-array
> > > +
> > > +  op-sink-microwatt:
> > > +    description: Sink required operating power in microwatt, if source can't
> > > +      offer the power, Capability Mismatch is set. Required for power sink and
> > > +      power dual role.
> > > +
> > > +  ports:
> > > +    description: OF graph bindings (specified in bindings/graph.txt) that model
> > > +      any data bus to the connector unless the bus is between parent node and
> > > +      the connector. Since a single connector can have multiple data buses every
> > > +      bus has assigned OF graph port number as described below.
> >
> > has an assigned?
> >
> > > +    type: object
> > > +    properties:
> > > +      port@0:
> > > +        type: object
> > > +        description: High Speed (HS), present in all connectors.
> > > +
> > > +      port@1:
> > > +        type: object
> > > +        description: Super Speed (SS), present in SS capable connectors.
> > > +
> > > +      port@2:
> > > +        type: object
> > > +        description: Sideband Use (SBU), present in USB-C.
> >
> > Likewise, is it possible to constrain this to only usb-c-connector
> > compatible string based bindings? And if so, does it become required for
> > that compatible string?
> 
> Not required as alternate modes are not required. (BTW, it should
> probably be clarified this is supposed to be the alternate mode
> connection of which SBU is part of).

I've changed the description text for port@2 to:
"Sideband Use (SBU), present in USB-C. This describes the alternate mode connection of which SBU is a part. "
> 
> Rob