linux-kernel - Re: [PATCH 3/4] drm/uapi: document the USB subconnector type

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Message-ID: <6097eb1d-6b00-4a0f-a91f-5b19f2b422eb@linaro.org>
Date:   Fri, 18 Aug 2023 13:30:56 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Simon Ser <contact@...rsion.fr>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Janne Grunau <j@...nau.net>, Robert Foss <rfoss@...nel.org>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Andy Gross <agross@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Jonas Karlman <jonas@...boo.se>, Leo Li <sunpeng.li@....com>,
        intel-gfx@...ts.freedesktop.org,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        "Pan, Xinhui" <Xinhui.Pan@....com>, linux-kernel@...r.kernel.org,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>
Subject: Re: [PATCH 3/4] drm/uapi: document the USB subconnector type

On 18/08/2023 09:24, Simon Ser wrote:
> On Thursday, August 17th, 2023 at 21:33, Dmitry Baryshkov <dmitry.baryshkov@...aro.org> wrote:
> 
>> We have been looking for a way to document that the corresponding DP
>> port is represented by the USB connector on the device.
>>
>> Consequently, I believe the best way to document it, would be to use
>> DisplayPort / USB, when there is no dongle connected, switching to
>> DisplayPort / HDMI, DisplayPort / VGA, DisplayPort / DisplayPort, etc.
>> when the actual dongle / display is connected and then switching back to
>> the DisplayPort / USB when it gets disconnected.
>>
>> If this sounds good to all parties, I'll post v2, adding this
>> explanation to the cover letter.
> 
> But how can user-space discover that the port is USB-C when it's
> connected? That information is lost at this point.

Yes, unfortunately.

> (In addition, this clashes with the existing semantics of the
> subconnector prop as discussed before: USB-C is not sub-, it's super-.)

Ok. How do we proceed then? Is it fine to add another property for DP 
case? Do you have any particular property name in mind? I will follow 
with addition of this property then.

-- 
With best wishes
Dmitry