Re: [RFC PATCH v1 00/12] drm,usb/typec: uABI for USB-C DisplayPort connectors

[Dmitry Baryshkov]

On 04/09/2023 18:46, Bjorn Andersson wrote:
> On Mon, Sep 04, 2023 at 12:41:38AM +0300, Dmitry Baryshkov wrote:
> > During the discussion regarding DisplayPort wrapped in the USB-C
> > connectors (via the USB-C altmode) it was pointed out that currently
> > there is no good way to let userspace know if the DRM connector in
> > question is the 'native' DP connector or if it is the USB-C connector.
> >
> > An attempt to use DRM_MODE_CONNECTOR_USB for such connectors was
> > declined, as existing DP drivers (i915, AMD) use
> > DRM_MODE_CONNECTOR_DisplayPort. New drivers should behave in the same
> > way.
>
> Sorry, didn't see the commit message before posting my complaint about
> USB -> DisplayPort.
>
> > An attempt to use subconnector property was also declined. It is defined
> > to the type of the DP dongle connector rather than the host connector.
> >
> > This attempt targets reusing the connector's PATH property. Currently
> > this property is only used for the DP MST connectors. This patchset
> > reuses it to point out to the corresponding registered typec port
> > device.
>
> Still interested in understanding how the path string should look like.

As wrote in the other letter, on RB5 it is 'typec:port0'. If the machine 
has two Type-C ports and two connected DP blocks, one of them will have 
'typec:port0', another one 'typec:port1'. This way one can further look 
under /sys/class/typec/portN/physical_localtion/ and find corresponding 
location, etc.

> Is the path expected to be consumed by machine, or is it only there for
> human convenience?

As with DP MST it is expected that userspace will consume this 
information, possibly renaming the connector. For example, on my laptop 
I have DP-1, ... DP-5 connectors (with DP-2 -- DP-5 being DP MST ones). 
Xorg renames them to DP-1, DP-2, DP-1-1, DP-1-2, DP-1-3, because the MST 
ones are branches for the DP-1.

--
With best wishes
Dmitry