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

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Message-ID: <576BD54A.8050800@ti.com>
Date:	Thu, 23 Jun 2016 15:25:46 +0300
From:	Roger Quadros <rogerq@...com>
To:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Oliver Neukum <oneukum@...e.com>
CC:	Felipe Balbi <felipe.balbi@...ux.intel.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Guenter Roeck <linux@...ck-us.net>,
	<linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>
Subject: Re: [PATCHv3 1/2] usb: USB Type-C connector class

Hi,

On 23/06/16 15:00, Heikki Krogerus wrote:
> Hi Oliver,
> 
> On Thu, Jun 23, 2016 at 10:38:58AM +0200, Oliver Neukum wrote:
>> On Thu, 2016-06-23 at 11:23 +0300, Heikki Krogerus wrote:
>>> On Wed, Jun 22, 2016 at 06:44:18PM +0200, Oliver Neukum wrote:
>>
>>> No it's not. DRP means a port that can operate as _either_ Source
>>> (host) or Sink (device), but not at the same time..
>>
>> Yes, but it is unclear what you will be after a connection
>> and that's the point.
> 
> Which is a fact that we can do nothing about. The role after
> connection with DRP ports will be dictated by the partner or selected
> randomly in case the partner is also DRP. We can prefer a role, but
> that in the end guarantees nothing. So if the role that we end up with
> after connection (seen in current_data_role) does not satisfy us, all
> we can do is try to swap it.
> 
> I'm not sure what is your point here.

What if the application wants to know exactly what role the device is
operating in at the current moment?

We need to have 2 distinct parameters.

1) supported_modes : host, device, host or device
2) current_mode: host, device, disconnected

--
cheers,
-roger