Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S944376AbdDTLzk (ORCPT ); Thu, 20 Apr 2017 07:55:40 -0400 Received: from mga03.intel.com ([134.134.136.65]:14510 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S943007AbdDTLzh (ORCPT ); Thu, 20 Apr 2017 07:55:37 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,225,1488873600"; d="scan'208";a="1121710597" Date: Thu, 20 Apr 2017 14:55:29 +0300 From: Heikki Krogerus To: Badhri Jagan Sridharan Cc: Oliver Neukum , Guenter Roeck , Mats Karrman , Greg KH , Felipe Balbi , LKML , USB Subject: Re: [PATCH v17 2/3] usb: USB Type-C connector class Message-ID: <20170420115529.GA4769@kuha.fi.intel.com> References: <20170303125940.GA6999@kuha.fi.intel.com> <6ddb2eac-03d5-127e-df1e-ad189968e6b2@gmail.com> <20170306131442.GC6999@kuha.fi.intel.com> <696552a7-c36a-1d73-9517-543907e9da39@gmail.com> <20170308135853.GH6999@kuha.fi.intel.com> <68817c44-d880-581a-e9f5-12845b9215eb@gmail.com> <20170419112323.GD24062@kuha.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.8.0 (2017-02-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1361 Lines: 36 Hi, On Wed, Apr 19, 2017 at 07:45:00AM -0700, Badhri Jagan Sridharan wrote: > >> What is the expected behavior when the userspace changes the > >> preferred_role node when the port is in connected state ? > >> > >> 1. the state machine re-resolves the port roles right away based on > >> the new state machine in place ? (or) > > > > No! There are separate attributes for sending role swap requests. > > Right. But, that might not be helpful in cases when PD is not implemented. > and Implementing PD is not mandatory according the spec :/ > > FYI quoting from the Type-C specification release(page 24), > role swaps are not limited to devices that only support PD. > > "Two independent set of mechanisms are defined to allow a USB Type-C > DRP to functionally swap power and data roles. When USB PD is > supported, power and data role swapping is performed as a subsequent > step following the initial connection process. For non-PD implementations, > power/data role swapping can optionally be dealt with as part of the initial > connection process." > > But, the current interface definition actually prevents current/data role > swaps for non-pd devices. No it doesn't. When USB PD is not supported, you can still use data_role to swap the role. Of course, the lower level driver may not support any role swapping in that case. Thanks, -- heikki