linux-kernel - Re: [PATCH 2/3] usb: type-c: USB Type-C Connector System Software Interface

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Message-ID: <20160218090704.GA13644@shlinux2>
Date:	Thu, 18 Feb 2016 17:07:04 +0800
From:	Peter Chen <hzpeterchen@...il.com>
To:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:	Felipe Balbi <balbi@...nel.org>, Oliver Neukum <oneukum@...e.com>,
	Felipe Balbi <balbif@...il.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: [PATCH 2/3] usb: type-c: USB Type-C Connector System Software
 Interface

On Wed, Feb 17, 2016 at 04:28:16PM +0200, Heikki Krogerus wrote:
> On Wed, Feb 17, 2016 at 03:36:46PM +0200, Felipe Balbi wrote:
> > 
> > Hi,
> > 
> 
> > IIRC mode and role negotiation goes via CC pins using the power delivery
> > protocol. If I misunderstand anything, let me know.
> 
> The data role swap with USB Type-C connectors is in no way tied to USB
> Power Delivery. The USB Type-C spec defines that when USB PD is
> available, DR_Swap USB PD function is used to swap the role, otherwise
> emulated disconnect will do the trick.
> 

I am interested in how you design role swap on the fly without USB PD.
Do you follow the spec like USB OTG 3.0 RSP (Role Swap Protocol) or
just echo the /sys to give up current role, and swap to another?

-- 

Best Regards,
Peter Chen