linux-kernel - Re: [PATCH 4/7] dt-bindings: drm/bridge: anx7625: Add mode-switch support

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Date:   Thu, 9 Jun 2022 11:24:35 -0700
From:   Prashant Malani <pmalani@...omium.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        bleung@...omium.org, swboyd@...omium.org,
        heikki.krogerus@...ux.intel.com,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>,
        José Expósito <jose.exposito89@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Maxime Ripard <maxime@...no.tech>,
        Neil Armstrong <narmstrong@...libre.com>,
        Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>, Pin-Yen Lin <treapking@...omium.org>,
        Robert Foss <robert.foss@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Xin Ji <xji@...logixsemi.com>
Subject: Re: [PATCH 4/7] dt-bindings: drm/bridge: anx7625: Add mode-switch support

On Wed, Jun 8, 2022 at 11:41 PM Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 08/06/2022 23:56, Prashant Malani wrote:
> > On Wed, Jun 8, 2022 at 10:08 AM Prashant Malani <pmalani@...omium.org> wrote:
> >>
> >> Hi Krzysztof,
> >>
> >> Thank you for looking at the patch.
> >>
> >> On Jun 08 11:24, Krzysztof Kozlowski wrote:
> >>> On 07/06/2022 21:00, Prashant Malani wrote:
> >>>> Analogix 7625 can be used in systems to switch USB Type-C DisplayPort
> >>>> alternate mode lane traffic between 2 Type-C ports.
> >>>>
> >>>> Update the binding to accommodate this usage by introducing a switch
> >>>> property.
> >>>>
> >>>> Signed-off-by: Prashant Malani <pmalani@...omium.org>
> >>>> ---
> >>>>  .../display/bridge/analogix,anx7625.yaml      | 56 +++++++++++++++++++
> >>>>  1 file changed, 56 insertions(+)
> >>>>
> >>>> diff --git a/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml b/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml
> >>>> index 35a48515836e..7e1f655ddfcc 100644
> >>>> --- a/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml
> >>>> +++ b/Documentation/devicetree/bindings/display/bridge/analogix,anx7625.yaml
> >>>> @@ -105,6 +105,26 @@ properties:
> >>>>        - port@0
> >>>>        - port@1
> >>>>
> >>>> +  switches:
> >>>> +    type: object
> >>>> +    description: Set of switches controlling DisplayPort traffic on
> >>>> +      outgoing RX/TX lanes to Type C ports.
> >>>> +
> >>>> +    properties:
> >>>> +      switch:
> >>>
> >>> You allow only one switch with such schema, so no need for "switches"...
> >>
> >> See below comment (summary: we'd like to allow 1 or 2 switches).
> >>>
> >>>> +        $ref: /schemas/usb/typec-switch.yaml#
> >>>> +        maxItems: 2
> >>>
> >>> Are you sure this works? what are you limiting here with maxItems? I
> >>> think you wanted patternProperties...
> >>
> >> Yeah, I might not have used the DT syntax correctly here.
> >> What I'm aiming for is:
> >> "switches" should can contain 1 or 2 "switch" nodes.
> >> 2 is the maximum (limitation of the hardware).
> >>
> >>>
> >>>> +
> >>>> +        properties:
> >>>> +          reg:
> >>>> +            maxItems: 1
> >>>> +
> >>>> +        required:
> >>>> +          - reg
> >>>> +
> >>>> +    required:
> >>>> +      - switch@0
> >>>
> >>> This does not match the property.
> >>>
> >>> You also need unevaluatedProperties:false
> >>
> >> Ack, will update this in the next version.
> >
> > Actually, could you kindly clarify which of the two needs this?
> > "switches" or "switch" ?
> > I interpreted "switch" as requiring it, but I thought it better to confirm.
>
> Depends what do you want to have there. If two properties called
> "switch", then "switches" is ok. However old code had only one property
> thus switches with maximum one switch is a bit weird.
>
> Looking at example you wanted to switch@[01], so you need to use
> patternProperties.

Thanks for the suggestion. I've made the change in v2.

Regards,

-Prashant