From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751915AbcBOPcy (ORCPT ); Mon, 15 Feb 2016 10:32:54 -0500 Received: from mx2.suse.de ([195.135.220.15]:54118 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751827AbcBOPcx (ORCPT ); Mon, 15 Feb 2016 10:32:53 -0500 Message-ID: <1455550218.22176.11.camel@suse.com> Subject: Re: [PATCH 2/3] usb: type-c: USB Type-C Connector System Software Interface From: Oliver Neukum To: Heikki Krogerus Cc: Greg KH , Felipe Balbi , Mathias Nyman , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org Date: Mon, 15 Feb 2016 16:30:18 +0100 In-Reply-To: <20160211135011.GA32213@kuha.fi.intel.com> References: <1455037283-106479-1-git-send-email-heikki.krogerus@linux.intel.com> <1455037283-106479-3-git-send-email-heikki.krogerus@linux.intel.com> <20160209182155.GC31787@kroah.com> <20160210103042.GB5270@kuha.fi.intel.com> <20160210172035.GA28335@kroah.com> <20160211135011.GA32213@kuha.fi.intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2016-02-11 at 15:50 +0200, Heikki Krogerus wrote: > Because USB Type-C ports (DRP ones) will select the data role randomly > when you connect (to an other DRP port). USB Type-C spec defines that > you can "prefer" host mode, but when both ends prefer host mode, it's > +-0. That question has not been answered. It would be awkward for the OS to find itself in the slave role, which it is ill equipped for. So the data role should be switched before the new device is announced to user space. How is that handled? Regards Oliver