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

From: Laurent Pinchart
Date: Thu Aug 03 2023 - 16:45:02 EST

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 ?

> However, in the USB-C case, DP itself is tunneled inside USB-C. And you
> might use a USB-C → DP adapter. So it's not really *sub*connector, it's
> more of a *super*connector, right?
> I think [1] is somewhat related, since it also allows user-space to
> discover whether a connector uses USB-C. But relying on sysfs to figure
> this out isn't super optimal perhaps.
> [1]:


Laurent Pinchart