Re: [PATCH v17 2/3] usb: USB Type-C connector class

[Guenter Roeck]

On 03/02/2017 07:22 AM, Mats Karrman wrote:
> Hi Heikki,
>
> Good to see things are happening with Type-C!
>
> On 2017-02-21 15:24, Heikki Krogerus wrote:
>
> > ...
> > +When connected, the partner will be presented also as its own device under
> > +/sys/class/typec/. The parent of the partner device will always be the port it
> > +is attached to. The partner attached to port "port0" will be named
> > +"port0-partner". Full path to the device would be
> > +/sys/class/typec/port0/port0-partner/.
>
> A "/port0" too much?
>
> > +
> > +The cable and the two plugs on it may also be optionally presented as their own
> > +devices under /sys/class/typec/. The cable attached to the port "port0" port
> > +will be named port0-cable and the plug on the SOP Prime end (see USB Power
> > +Delivery Specification ch. 2.4) will be named "port0-plug0" and on the SOP
> > +Double Prime end "port0-plug1". The parent of a cable will always be the port,
> > +and the parent of the cable plugs will always be the cable.
> > +
> > +If the port, partner or cable plug support Alternate Modes, every supported
> > +Alternate Mode SVID will have their own device describing them. The Alternate
> > +Modes will not be attached to the typec class. The parent of an alternate mode
> > +will be the device that supports it, so for example an alternate mode of
> > +port0-partner will bees presented under /sys/class/typec/port0-partner/. Every
>
> bees?
>
> > +mode that is supported will have its own group under the Alternate Mode device
> > +named "mode<index>", for example /sys/class/typec/port0/<alternate mode>/mode1/.
> > +The requests for entering/exiting a mode can be done with "active" attribute
> > +file in that group.
> > +
> > ...
>
> I'm hoping to find time to upgrade the kernel and try these patches in my system.
>
> Looking forward, one thing I have run into is how to connect the typec driver with a
> driver for an alternate mode. E.g. the DisplayPort Alternate Mode specification
> includes the HPD (hot plug) and HPD-INT (hot plug interrupt) signals as bits in the
> Attention message. These signals are needed by the DisplayPort driver to know when to
> start negotiation etc.
> Have you got any thoughts on how to standardize such interfaces?

That really depends on the lower level driver. For Chromebooks, where the Type-C
Protocol Manager runs on the EC, we have an extcon driver which reports the pin states
to the graphics drivers and connects to the Type-C class code using the Type-C class
API. I still need to update, re-test, and publish that code. The published code in
https://chromium.googlesource.com/chromiumos/third_party/kernel/, branch chromeos-4.4,
shows how it can be done, though that code currently still uses the Android Type-C
infrastructure.

Guenter