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

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Message-ID: <573FF752.2080204@roeck-us.net>
Date:	Fri, 20 May 2016 22:51:14 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Oliver Neukum <oneukum@...e.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:	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 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.

Guenter