From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934445AbbDIJYN (ORCPT ); Thu, 9 Apr 2015 05:24:13 -0400 Received: from mailout1.w1.samsung.com ([210.118.77.11]:15848 "EHLO mailout1.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934426AbbDIJYJ (ORCPT ); Thu, 9 Apr 2015 05:24:09 -0400 X-AuditID: cbfec7f4-b7f106d0000013ec-2f-552644884760 Message-id: <55264534.4020006@samsung.com> Date: Thu, 09 Apr 2015 11:24:04 +0200 From: Robert Baldyga User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-version: 1.0 To: Chanwoo Choi Cc: myungjoo.ham@samsung.com, rogerq@ti.com, linux-usb@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, m.szyprowski@samsung.com Subject: Re: [PATCH v3 2/4] extcon: usb-gpio: add support for VBUS detection References: <1427980385-21285-1-git-send-email-r.baldyga@samsung.com> <1427980385-21285-3-git-send-email-r.baldyga@samsung.com> <5525E012.5050207@samsung.com> <552630E4.9030309@samsung.com> <55264148.8070903@samsung.com> In-reply-to: <55264148.8070903@samsung.com> Content-type: text/plain; charset=windows-1252 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrALMWRmVeSWpSXmKPExsVy+t/xq7odLmqhBnvO6Ftc//Kc1WL+kXOs Fpd3zWGzWLSsldli7ZG77Ba3G1ewWfQ80nJg9+jbsorR4/iN7UwenzfJBTBHcdmkpOZklqUW 6dslcGWcef+AseAzb8XVCW4NjH+4uhg5OSQETCQOHjvMCmGLSVy4t56ti5GLQ0hgKaNEX8sL FgjnI6PE+zkvGUGqeAW0JOZ9esAGYrMIqErM6N/KAmKzCehIbPk+AaiGg0NUIELi9mVOiHJB iR+T74GViAhoSMz8e4URZCazwDxGicVz37OD1AsL+EgsvMEKsesRo8Sx79PAGjgFtCXOLD3I ClLDLKAncf+iFkiYWUBeYvOat8wTGAVmIVkxC6FqFpKqBYzMqxhFU0uTC4qT0nMN9YoTc4tL 89L1kvNzNzFCQvnLDsbFx6wOMQpwMCrx8FocUwkVYk0sK67MPcQowcGsJMIbba4WKsSbklhZ lVqUH19UmpNafIiRiYNTqoExUkD+zLxlWhbn5661mCgtrsA1pXvqPnvT6YGbmf4tblRhjJty cpUf56JdUjUvGgykZeKz/J1vfbz3SaPFPnjmu/0XAs1lnTONTu/6uuFElJSR0hWhFdyySrvU Ez4EOR6oU3xy4WPi1lcc1ltssl6vbGP9fF8gc5rrlm2vVnRe2sr6wuor70JZJZbijERDLeai 4kQAaQY0mkMCAAA= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Chanwoo, On 04/09/2015 11:07 AM, Chanwoo Choi wrote: > Hi Robert, > > On 04/09/2015 04:57 PM, Robert Baldyga wrote: >> Hi Chanwoo, >> >> On 04/09/2015 04:12 AM, Chanwoo Choi wrote: >>> Hi Robert, >>> > > [snip] > >>> But, I have one question about case[3] >>> >>> If id is low and vbus is high, this patch will update the state of both USB and USB-HOST cable as attached state. >>> Is it possible that two different cables (both USB and USB-HOST) are connected to one port simultaneously? >>> >> >> It's because state of single USB cable connection cannot be completely >> described using single extcon cable. USB cable state has two bits (VBUS >> and ID), so we need to use two cables for single cable connection. We >> use following convention: >> cable "USB" = VBUS >> cable "USB-HOST" = !ID. > > I think that extcon provider driver have to update the only one cable state > of either USB or USB-HOST because USB and USB-HOST feature can not be used > at the same time through one h/w port. > > If extcon-usb-gpio.c update two connected event of both USB and USB-HOST cable > at the same time, the extcon consumer driver can not decide what handle either USB or USB-HOST. > It can. USB OTG allows for that. Moreover device can be host even if ID=1 (so detected cable type is USB device), or peripheral when ID=0 (so detected cable type is USB host). Devices would need to have complete information about USB cable connection, because OTG state machine needs that. As I wrote, current USB cable names are misleading. It would be better to have "USB-VBUS" and "USB-ID". >> In fact it would be better to have cables named "USB-VBUS" and "USB-ID" >> - in this convention it would be more clear. Thanks, Robert Baldyga