linux-kernel - Re: [PATCH v2 8/9] media: dt-bindings: Add Intel Displayport RX IP

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Date: Mon, 26 Feb 2024 13:43:55 +0100
From: Paweł Anikiel <panikiel@...gle.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: airlied@...il.com, akpm@...ux-foundation.org, conor+dt@...nel.org, 
	daniel@...ll.ch, dinguyen@...nel.org, hverkuil-cisco@...all.nl, 
	krzysztof.kozlowski+dt@...aro.org, maarten.lankhorst@...ux.intel.com, 
	mchehab@...nel.org, mripard@...nel.org, robh+dt@...nel.org, 
	tzimmermann@...e.de, devicetree@...r.kernel.org, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	linux-media@...r.kernel.org, chromeos-krk-upstreaming@...gle.com, 
	ribalda@...omium.org
Subject: Re: [PATCH v2 8/9] media: dt-bindings: Add Intel Displayport RX IP

On Mon, Feb 26, 2024 at 1:06 PM Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
>
> On 26/02/2024 11:59, Paweł Anikiel wrote:
> >>> +properties:
> >>> +  compatible:
> >>> +    const: intel,dprx-20.0.1
> >>> +
> >>> +  reg:
> >>> +    maxItems: 1
> >>> +
> >>> +  interrupts:
> >>> +    maxItems: 1
> >>> +
> >>> +  intel,max-link-rate:
> >>> +    $ref: /schemas/types.yaml#/definitions/uint32
> >>> +    description: Max link rate configuration parameter
> >>
> >> Please do not duplicate property name in description. It's useless.
> >> Instead explain what is this responsible for.
> >>
> >> Why max-link-rate would differ for the same dprx-20.0.1? And why
> >> standard properties cannot be used?
> >>
> >> Same for all questions below.
> >
> > These four properties are the IP configuration parameters mentioned in
> > the device description. When generating the IP core you can set these
> > parameters, which could make them differ for the same dprx-20.0.1.
> > They are documented in the user guide, for which I also put a link in
> > the description. Is that enough? Or should I also document these
> > parameters here?
>
> user-guide is something for users, like user-space programmers or
> end-users. I would never open it to look for any information related to
> hardware.
>
> Anyway, external resources are a no-go. We have it clearly in submitting
> patches:
>
> https://elixir.bootlin.com/linux/v6.8-rc6/source/Documentation/process/submitting-patches.rst#L130

Okay, I will describe these properties in the bindings as well.

>
> >
> >>
> >>> +
> >>> +  intel,max-lane-count:
> >>> +    $ref: /schemas/types.yaml#/definitions/uint32
> >>> +    description: Max lane count configuration parameter
> >>> +
> >>> +  intel,multi-stream-support:
> >>> +    type: boolean
> >>> +    description: Multi-Stream Transport support configuration parameter
> >>> +
> >>> +  intel,max-stream-count:
> >>> +    $ref: /schemas/types.yaml#/definitions/uint32
> >>> +    description: Max stream count configuration parameter
> >>> +
> >>> +  port:
> >>> +    $ref: /schemas/graph.yaml#/properties/port
> >>> +    description: SST main link
> >>
> >> I don't understand why you have both port and ports. Shouldn't this be
> >> under ports?
> >
> > I put both so that you can use the shorter port property when the
> > device only has one port (i.e. no MST support). It would work fine
> > without it. If you think that's unnecessary, I can remove it (and use
> > the ports property even if there is only one).
>
> No, it is fine, but then you need allOf: which will restrict to only one
> of them: either port or ports.

There already is an allOf below that says that ports is required for
MST support and port is required otherwise. Isn't this enough?