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Date:   Thu, 03 Aug 2023 15:43:25 +0000
To:     Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
From:   Simon Ser <contact@emersion.fr>
Cc:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
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        Leo Li <sunpeng.li@amd.com>,
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Subject: Re: [PATCH 3/4] drm/uapi: document the USB subconnector type
Message-ID: <C-Fu9j3hts_YcQxukEbidrKyTdqYNxYuWUX-694HnmYKiJGZip24s6R8-dULdTvb2VE972he3PZlju2K9wFNkA9j-XKUGemuWiFLGT1eUu0=@emersion.fr>
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References: <20230729004913.215872-1-dmitry.baryshkov@linaro.org> <20230729004913.215872-4-dmitry.baryshkov@linaro.org> <20230802185547.GC32500@pendragon.ideasonboard.com> <a32ce695-038f-0ef8-3584-5bd1ba528131@linaro.org> <20230802191351.GA1407@pendragon.ideasonboard.com> <DE2B4523-D16C-4AFC-8352-212B23548DD5@linaro.org> <b6oOVz2YMIG4hJDWhq9lTh6R2HYcrpRwHENhplig9KSQMD8dIjTgC5KdH1Ij3URgV2HESp67Ax7QUsByGjMLouvbs-5q7PiPRdLkgJz6Fwk=@emersion.fr> <ADjuOeqA6575DKutMPaR9mW9rLhm-wjLc4ruoUkNwImf-GB90FdwDB7v7y6LFdzVG3BC4R52A0RUtStK4_smmGYTUs3UPDOX4T4Zl2YHkxE=@emersion.fr> <CAA8EJppCECObEe5UG3LsHUsmYfKzakWzVw33S4nVc=DB9sA0ig@mail.gmail.com>
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On Thursday, August 3rd, 2023 at 17:36, Dmitry Baryshkov <dmitry.baryshkov@=
linaro.org> wrote:

> On Thu, 3 Aug 2023 at 18:31, Simon Ser contact@emersion.fr wrote:
>=20
> > On Thursday, August 3rd, 2023 at 17:22, Simon Ser contact@emersion.fr w=
rote:
> >=20
> > > The KMS docs describe "subconnector" to be defined as "downstream por=
t" for DP.
> > > Can USB-C (or USB) be seen as a DP downstream port?
> >=20
> > To expand on this a bit: I'm wondering if we're mixing apples and
> > oranges here. The current values of "subconnector" typically describe
> > the lower-level protocol tunneled inside DP. For instance, VGA can be
> > tunneled inside the DP cable when using DP =E2=86=92 VGA adapter.
>=20
> My opinion hasn't changed: I think this should be the USB connector
> with proper DP / DVI / HDMI / etc. subconnector type (or lack of it).
> In the end, the physical connector on the side of laptop is USB-C.

- Even if the connector is USB-C, the protocol used for display is
  still DP. There's also the case of Thunderbolt.
- This is inconsistent with existing drivers. i915 and amdgpu expose
  DP ports for their USB-C ports. Changing that isn't possible without
  causing user-space regressions (compositor config files use the
  connector type).