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

[Simon Ser]

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.

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]: https://lore.kernel.org/dri-devel/20221108185004.2263578-1-wonchung@xxxxxxxxxx/