Date:   Tue, 11 Feb 2020 11:01:46 -0800
From:   Prashant Malani <pmalani@...omium.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        heikki.krogerus@...el.com, Benson Leung <bleung@...omium.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Guenter Roeck <groeck@...omium.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v2 1/4] dt-bindings: Add cros-ec Type C port driver

Resending (because I didn't send it in PlainText mode, so the MLs
blocked the email). Sorry.


On Tue, Feb 11, 2020 at 11:00 AM Prashant Malani <pmalani@...omium.org> wrote:
>
> Hi Enric,
>
> Thanks as always for reviewing the patch. Kindly see my responses inline:
>
> On Tue, Feb 11, 2020 at 2:28 AM Enric Balletbo i Serra <enric.balletbo@...labora.com> wrote:
>>
>> Hi Prashant,
>>
>> On 7/2/20 21:37, Prashant Malani wrote:
>> > Some Chrome OS devices with Embedded Controllers (EC) can read and
>> > modify Type C port state.
>> >
>> > Add an entry in the DT Bindings documentation that lists out the logical
>> > device and describes the relevant port information, to be used by the
>> > corresponding driver.
>> >
>> > Signed-off-by: Prashant Malani <pmalani@...omium.org>
>> > ---
>> >
>> > Changes in v2:
>> > - No changes. Patch first introduced in v2 of series.
>> >
>> >  .../bindings/chrome/google,cros-ec-typec.yaml | 77 +++++++++++++++++++
>> >  1 file changed, 77 insertions(+)
>> >  create mode 100644 Documentation/devicetree/bindings/chrome/google,cros-ec-typec.yaml
>> >
>> > diff --git a/Documentation/devicetree/bindings/chrome/google,cros-ec-typec.yaml b/Documentation/devicetree/bindings/chrome/google,cros-ec-typec.yaml
>> > new file mode 100644
>> > index 00000000000000..46ebcbe76db3c2
>> > --- /dev/null
>> > +++ b/Documentation/devicetree/bindings/chrome/google,cros-ec-typec.yaml
>> > @@ -0,0 +1,77 @@
>> > +# SPDX-License-Identifier: GPL-2.0
>>
>> I think that Google is fine with the dual licensing here. Would be good if this
>> can be (GPL-2.0-only OR BSD-2-Clause)
>
>
> Thanks for catching this. I will update it in the next version.
>>
>>
>> > +%YAML 1.2
>> > +---
>> > +$id: http://devicetree.org/schemas/chrome/google,cros-ec-typec.yaml#
>> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> > +
>> > +title: Google Chrome OS EC(Embedded Controller) Type C port driver.
>> > +
>> > +maintainers:
>> > +  - Benson Leung <bleung@...omium.org>
>> > +  - Prashant Malani <pmalani@...omium.org>
>> > +
>> > +description:
>> > +  Chrome OS devices have an Embedded Controller(EC) which has access to
>> > +  Type C port state. This node is intended to allow the host to read and
>> > +  control the Type C ports. The node for this device should be under a
>> > +  cros-ec node like google,cros-ec-spi.
>> > +
>> > +properties:
>> > +  compatible:
>> > +    const: google,cros-ec-typec
>> > +
>> > +  port:
>> > +    description: A node that represents a physical Type C port on the
>> > +      device.
>> > +    type: object
>> > +    properties:
>> > +      port-number:
>> > +        description: The number used by the Chrome OS EC to identify
>> > +          this type C port.
>> > +        $ref: /schemas/types.yaml#/definitions/uint32
>>
>> Any range of values allowed? 0 is okay?
>
>
> 0 is acceptable. Looks like Chrome OS EC numbers the ports as 0 to (num_ports - 1).
> Actually, looking at it more closely, the port info EC command struct uses uint8_t (https://elixir.bootlin.com/linux/latest/source/include/linux/platform_data/cros_ec_commands.h#L4879)
> Also, num_ports cannot be larger than: https://elixir.bootlin.com/linux/latest/ident/EC_USB_PD_MAX_PORTS
>
> So perhaps this should be updated to say it can be any value from 0 - EC_USB_PD_MAX_PORTS ? (Not sure if I can reference #defines from header files in the DT bindings file....)
>>
>>
>> > +      power-role:
>>
>> Sorry if this question is silly, aren't this and below properties the same as
>> provided by usb-connector?  Can't this be usb-c-connector?
>>
>> Documentation/devicetree/bindings/connector/usb-connector.txt
>
>
> That's correct, it is the same. I think there is a slight difference between the properties of usb-connector (what properties are defined as optional and required) so I don't know if we can re-use usb-connector.
> TBH I wasn't sure about this myself. I am also not sure whether there will be an issue with usb-c-connector being "claimed" by another driver. I think Heikki could perhaps guide us here.
>>
>>
>> > +        description: Determines the power role that the Type C port will
>> > +          adopt.
>> > +        oneOf:
>> > +          - items:
>> > +            - const: sink
>> > +            - const: source
>> > +            - const: dual
>> > +      data-role:
>> > +        description: Determines the data role that the Type C port will
>> > +          adopt.
>> > +        oneOf:
>> > +          - items:
>> > +            - const: host
>> > +            - const: device
>> > +            - const: dual
>> > +      try-power-role:
>> > +        description: Determines the preferred power role of the Type C port.
>> > +        oneOf:
>> > +          - items:
>> > +            - const: sink
>> > +            - const: source
>> > +            - const: dual
>> > +
>> > +    required:
>> > +      - port-number
>> > +      - power-role
>> > +      - data-role
>> > +      - try-power-role
>> > +
>> > +required:
>> > +  - compatible
>> > +  - port
>> > +
>> > +examples:
>> > +  - |+
>>
>> Rob can confirm, but I think is a good practice add the parent node, so add the
>> cros-ec-spi node here?
>
> Done. Will add it in the next version.
>>
>>
>> > +    typec {
>> > +      compatible = "google,cros-ec-typec";
>> > +
>> > +      port@0 {
>>
>> You can run:
>>
>>   make dt_binding_check DT_SCHEMA_FILES=<...>/chrome/google,cros-ec-typec.yaml
>>
>> And you'll get an error:
>>
>>  typec: 'port' is a required property
>
> Noted. I will run this check before pushing next time and fix the error.
>>
>>
>> > +        port-number = <0>;
>> > +        power-role = "dual";
>> > +        data-role = "dual";
>> > +        try-power-role = "source";
>> > +      };
>> > +    };
>> >
>> Thanks,
>>
>>  Enric
>
>
>
> Thanks,
>
> -Prashant

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