Re: [PATCHv3 1/2] usb: USB Type-C connector class
From: Heikki Krogerus
Date: Wed Jun 22 2016 - 06:05:46 EST
On Wed, Jun 22, 2016 at 12:50:16PM +0300, Heikki Krogerus wrote:
> On Tue, Jun 21, 2016 at 10:25:05PM +0200, Oliver Neukum wrote:
> > On Tue, 2016-06-21 at 17:51 +0300, Heikki Krogerus wrote:
> > > +What: /sys/class/typec/<port>/supported_data_roles
> > > +Data: June 2016
> > > +Contact: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> > > +Description:
> > > + Lists the USB data roles, host or device, the port is
> > > capable
> > > + of supporting.
> >
> > On third thought, this is a problem. Looking at 4.4.8.1
> > DEVICE_CAPABILITIES (Required) of USB Type-C Port Controller
> > Interface Specification we lack capability.
> >
> > A port that can do DRP is not the same thing as a port that
> > can be switched between DFP and UFP. We cannot express that.
>
> What do you mean? DRP means we support and are able to swap the data
> role, but it just does not mean we can act as both source and sink. And
> that information we already get from separate attribute:
> "supported_power_roles".
>
> But if the port is DRP, we will always be able to swap the data role
> between DFP and UFP.
Just to clarify: DRP as it's defined in Type-C spec < 1.2 means the
data role, not power role. And that is what Universal Serial Bus
Type-CTM Port Controller specification is based on. Please correct me
if I'm wrong.
Thanks,
--
heikki