Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754897AbbDJHpp (ORCPT ); Fri, 10 Apr 2015 03:45:45 -0400 Received: from mailout3.w1.samsung.com ([210.118.77.13]:49302 "EHLO mailout3.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753615AbbDJHpm (ORCPT ); Fri, 10 Apr 2015 03:45:42 -0400 X-AuditID: cbfec7f4-b7f106d0000013ec-66-55277ef6b55f Message-id: <55277FA2.6090700@samsung.com> Date: Fri, 10 Apr 2015 09:45:38 +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> <55264534.4020006@samsung.com> <55277910.2070000@samsung.com> In-reply-to: <55277910.2070000@samsung.com> Content-type: text/plain; charset=windows-1252 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrALMWRmVeSWpSXmKPExsVy+t/xy7rf6tRDDa63sFtc//Kc1WL+kXOs Fpd3zWGzWLSsldli7ZG77Ba3G1ewWfQ80nJg9+jbsorR4/iN7UwenzfJBTBHcdmkpOZklqUW 6dslcGXcPvadreC1SMX33wuYGhj3C3QxcnJICJhIvDu0mxnCFpO4cG89WxcjF4eQwFJGieeb ZjKCJIQEPjJK/HhSD2LzCmhJ3HvylRXEZhFQldjX0cMOYrMJ6Ehs+T4BqJ6DQ1QgQuL2ZU6I ckGJH5PvsYDYIgIaEjP/XmEEmc8sMI9RYvHc9+wg9cICPhILb7BC7F3EJPH12nqwmZwC2hKn D5wGq2EW0JO4f1ELJMwsIC+xec1b5gmMArOQrJiFUDULSdUCRuZVjKKppckFxUnpuYZ6xYm5 xaV56XrJ+bmbGCGh/GUH4+JjVocYBTgYlXh4A4zVQ4VYE8uKK3MPMUpwMCuJ8FbGAoV4UxIr q1KL8uOLSnNSiw8xMnFwSjUwZnA/Of/d5HHymwls056ZC3v0bf8m4C6Vpx1/cDGXfu4jWZZJ vzd8FPA4teCk9iZ+5ci2stNa9W6l/6R8tYpj3C9uvVKUVfVE0X3Z+af6dxaeC2uSSz+j5/yh lrliwpnwI9u6eyZmXFpWt+sVu2CzimqZNH+mvp2cRFJtURTv8kWGUe1hLUFKLMUZiYZazEXF iQDVCvD9QwIAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2843 Lines: 74 On 04/10/2015 09:17 AM, Chanwoo Choi wrote: > Hi Robert, > > On 04/09/2015 06:24 PM, Robert Baldyga wrote: >> 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 > > As I knew, USB OTG port don't send the attached cable of both USB and USB-HOST > at the same time. The case3 in your patch update two cable state about one h/w port. > It's because simple "USB" or "USB-HOST" means nothing for USB OTG machine. It needs to know exact VBUS and ID states, which cannot be concluded basing on cable type only. That's why I have used "USB-HOST" name together with "USB" to pass additional information about USB cable connection. > I don't agree. > >> that. As I wrote, current USB cable names are misleading. It would be >> better to have "USB-VBUS" and "USB-ID". > > It is strange cable name. I prefer to use only 'USB' cable name. > But, we could support the other method to get the state of whether USB-VBUS or USB-ID > by using helper API or others. > Ok, so do you have any idea how to do it? Do we want to supply additional API for notifying about VBUS and ID changes? Thanks, Robert Baldyga -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/