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

[Dmitry Baryshkov]

On Thu, 3 Aug 2023 at 23:47, Simon Ser <contact@xxxxxxxxxxx> wrote:
>
> On Thursday, August 3rd, 2023 at 22:44, Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
>
> > On Thu, Aug 03, 2023 at 03:31:16PM +0000, Simon Ser wrote:
> >
> > > On Thursday, August 3rd, 2023 at 17:22, Simon Ser contact@xxxxxxxxxxx wrote:
> > >
> > > > The KMS docs describe "subconnector" to be defined as "downstream port" for DP.
> > > > Can USB-C (or USB) be seen as a DP downstream port?
> > >
> > > 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 → VGA adapter.
> >
> > Doesn't this contradict the example use case you gave in your previous
> > e-mail, with wlroots stating "DP-3 via DVI-D" ? I understand that as DP
> > carried over a DVI-D physical connector, did I get it wrong ?
>
> No, this is DVI carried over DP. DP cannot be carried over VGA/DVI/HDMI,
> but VGA/DVI/HDMI can be carried over DP.

Well, not quite. It means that the sink (display) connected to this
port identifies itself as an VGA / DVI / HDMI monitor.
E.g. on if connect HDMI/DVI monitor through the DP-DVI dongle (native
DP connector), AMD driver still identifies it as 'subconnector HDMI',
despite dongle a DVI connector on the other side.

-- 
With best wishes
Dmitry