Re: [PATCHv3 1/2] usb: USB Type-C connector class

From: Oliver Neukum
Date: Wed Jun 22 2016 - 09:51:33 EST


On Wed, 2016-06-22 at 14:44 +0300, Heikki Krogerus wrote:
> If our port is DRD (which would be DRP in the port controller spec),
> the supported_power_roles will list:
>
> device, host
>
> And the power role, if the port is Source only, the
> supported_power_roles will list:
>
> source
>
> If the port is Sink only, the supported_power_roles will list:
>
> sink
>
> If our port is DRP, the supported_power_roles will list:
>
> source, sink
>
> What is there that is missing? We are able to express all the types of
> "Roles Supported" that the DEVICE_CAPABILITIES define, no?

No, because these are distinct in time. Some ports are DRP so they
support

device, host

at the same time. Some ports can be switched between DFP and UFP
they then either support host or device. But you lose the information
that the ports can be switched.

Regards
Oliver