linux-kernel - Re: [RFC PATCHv2] usb: USB Type-C Connector Class

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Message-ID: <1463813039.24976.9.camel@suse.com>
Date:	Sat, 21 May 2016 08:43:59 +0200
From:	Oliver Neukum <oneukum@...e.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Rajaram R <rajaram.officemail@...il.com>,
	Felipe Balbi <felipe.balbi@...ux.intel.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [RFC PATCHv2] usb: USB Type-C Connector Class

On Fri, 2016-05-20 at 22:51 -0700, Guenter Roeck wrote:
> On 05/20/2016 06:37 AM, Oliver Neukum wrote:
> > On Fri, 2016-05-20 at 14:24 +0300, Heikki Krogerus wrote:
> >> On Thu, May 19, 2016 at 04:47:17PM +0200, Oliver Neukum wrote:
> >>>
> >>> Please explain. How does that express DRP but prefered master?
> >>
> >> Sorry but I'm not sure what you mean here. If the port is capable of
> >> being used as dual role port (DRP in the supported_data_roles file),
> >> that is the only case where you can select the role with this file. So
> >> I would imagine that in your case you want to make the port act as
> >> DFP only, right? But if the port is capable of acting only as UFP, you
> >> are stuck with that role.
> >
> > How do I trigger that Try.SRC is to be used on a port?
> >
> 
> This would be part of the USB PD protocol, ie probably outside the scope
> of the class code. In my implementation, I enable Try.SRC or Try.SNK based
> on the platform's preferred role.

Hi,

from a purely formal point of view that makes sense.

>From a usability viewpoint I'd ideally want all controls
for role at one place. And possibly the controls for modes
at the same place.

I think part of the problem here is that we lack a statement
of mission. What are these controls for?
Merely for controlling modes and providing information
about modes? And to use neutral terms only for the "master"
side or both sides?

	Regards
		Oliver