linux-kernel - Re: [PATCH v4 1/2] dt-bindings: drm/bridge: ti-tmds181: Add TI TMDS181 and SN65DP159 bindings

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Message-ID: <fccbba0a-cb8f-4d71-9c91-7558cfaa8ef7@topic.nl>
Date: Tue, 2 Sep 2025 16:41:57 +0200
From: Mike Looijmans <mike.looijmans@...ic.nl>
To: Krzysztof Kozlowski <krzk@...nel.org>
CC: dri-devel@...ts.freedesktop.org, Andrzej Hajda <andrzej.hajda@...el.com>,
 Conor Dooley <conor+dt@...nel.org>, David Airlie <airlied@...il.com>,
 Jernej Skrabec <jernej.skrabec@...il.com>, Jonas Karlman <jonas@...boo.se>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>,
 Neil Armstrong <neil.armstrong@...aro.org>, Rob Herring <robh@...nel.org>,
 Robert Foss <rfoss@...nel.org>, Simona Vetter <simona@...ll.ch>,
 Thomas Zimmermann <tzimmermann@...e.de>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] dt-bindings: drm/bridge: ti-tmds181: Add TI
 TMDS181 and SN65DP159 bindings

On 9/2/25 15:46, Krzysztof Kozlowski wrote:
> On 02/09/2025 10:46, Mike Looijmans wrote:
>>>> +          endpoint:
>>>> +            $ref: /schemas/media/video-interfaces.yaml#
>>>> +            unevaluatedProperties: false
>>>> +
>>>> +      port@1:
>>>> +        $ref: /schemas/graph.yaml#/$defs/port-base
>>>> +        unevaluatedProperties: false
>>>> +        description: Video port for HDMI output (panel or bridge)
>>>> +
>>>> +        properties:
>>>> +          endpoint:
>>>> +            $ref: /schemas/media/video-interfaces.yaml#
>>>> +            unevaluatedProperties: false
>>>> +
>>>> +    required:
>>>> +      - port@0
>>>> +      - port@1
>>>> +
>>>> +  ti,source-mode:
>>>> +    type: boolean
>>>> +    description:
>>>> +      Force chip to operate in "source" mode. Allows to use
>>>> +      a TMDS181 chip (which defaults to sink) as cable driver.
>>>> +
>>>> +  ti,sink-mode:
>>> Aren't these two mutually exclusive? Can same device operate in source
>>> and in sink mode simultaneously?
>> They're exclusive, yes. Will add that.
> Then either define constraints per variant in if:then: or maybe better
> use string enum. Not sure what applies where, so tricky to say which
> choice is better.
>
> Best regards,
> Krzysztof

Since there's already going to be an "if" block, it simplifies parsing 
to keep the booleans. My first attempt was this, but that doesn't work 
as I'd expect. Adding "slew-rate" to the example dts results in an 
error, so apparently the "if" block doesn't do what I think it would and 
I haven't figured out yet what the correct syntax must be:

if:
   properties:
     compatible:
       contains:
         const: ti,sn65dp159
then:
   properties:
     ti,sink-mode:
       type: boolean
       description:
         Force chip to operate in "sink" mode. Allows to use
         a DP159 chip (defaults to source) for incoming signals.
     ti,dvi-mode:
       type: boolean
       description: Makes the DP159 chip operate in DVI mode.
     slew-rate:
       $ref: /schemas/types.yaml#/definitions/uint32
       minimum: 0
       maximum: 3
       default: 3
       description: Set slew rate, 0 is slowest, 3 is fastest.
else:
   properties:
     ti,source-mode:
       type: boolean
       description:
         Force chip to operate in "source" mode. Allows to use
         a TMDS181 chip (which defaults to sink) as cable driver.

-- 
Mike Looijmans
System Expert

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