Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755817AbbDJJSS (ORCPT ); Fri, 10 Apr 2015 05:18:18 -0400 Received: from mailout3.samsung.com ([203.254.224.33]:29833 "EHLO mailout3.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754111AbbDJJSM (ORCPT ); Fri, 10 Apr 2015 05:18:12 -0400 X-AuditID: cbfee68e-f79c56d000006efb-05-55279550233a Message-id: <55279550.1060609@samsung.com> Date: Fri, 10 Apr 2015 18:18:08 +0900 From: Chanwoo Choi User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-version: 1.0 To: Robert Baldyga 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> <55277FA2.6090700@samsung.com> <55278580.2090809@samsung.com> <55278DD3.3020409@samsung.com> In-reply-to: <55278DD3.3020409@samsung.com> Content-type: text/plain; charset=windows-1252 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprGIsWRmVeSWpSXmKPExsWyRsSkRDdwqnqowbFmJov5R86xWlzeNYfN YtGyVmaLtUfuslvcblzBZvHg8E52i55HWg7sHn1bVjF6HL+xncnj8ya5AOYoLpuU1JzMstQi fbsEroxJB8ILrspX7JveydzAuEWyi5GTQ0LAROLLu73MELaYxIV769lAbCGBpYwSb7plYGo2 HbvC0sXIBRRfxCix+PlXdgjnAaPEoYPPmUCqeAW0JO7f+cMCYrMIqEpsvfMbzGYDiu9/cQNs qqhAmMTK6VdYIOoFJX5MvgdmiwDV3Pk4H2wos8A8oA1z3wM5HBzCAj4SC2+wQixrZJbY0NTA CtLAKaAtseXtNTaQGmYBPYn7F7VAwswC8hKb17xlBqmXENjFLnHt4WRWiIMEJL5NPsQCUi8h ICux6QDUx5ISB1fcYJnAKDYLyUmzEKbOQjJ1ASPzKkbR1ILkguKk9CIjveLE3OLSvHS95Pzc TYzA6Dr971nfDsabB6wPMQpwMCrx8DbEqocKsSaWFVfmHmI0BTpiIrOUaHI+MIbzSuINjc2M LExNTI2NzC3NlMR5E6R+BgsJpCeWpGanphakFsUXleakFh9iZOLglGpgTN26+XKriPtvdRfd 6CU7Ui0C5/0K6HxTPiF6/ZbKeTfleuUfVh781vdygVjy9S3T2V9eTRfUXf530+7zy7b5L5iy 0S3vWcVhi5z1/rdFdgq6HM9QTred7LlW+e6UbUlzLudJ5t10fby34PqcnUUruZ772WcbcXT8 mJ/T8zvgY9XXmg3uGl1T3iixFGckGmoxFxUnAgBp6Tc7qQIAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrIIsWRmVeSWpSXmKPExsVy+t9jAd2AqeqhBm+emFnMP3KO1eLyrjls FouWtTJbrD1yl93iduMKNosHh3eyW/Q80nJg9+jbsorR4/iN7UwenzfJBTBHNTDaZKQmpqQW KaTmJeenZOal2yp5B8c7x5uaGRjqGlpamCsp5CXmptoqufgE6Lpl5gAtV1IoS8wpBQoFJBYX K+nbYZoQGuKmawHTGKHrGxIE12NkgAYS1jBmTDoQXnBVvmLf9E7mBsYtkl2MnBwSAiYSm45d YYGwxSQu3FvP1sXIxSEksIhRYvHzr+wQzgNGiUMHnzOBVPEKaEncv/MHrINFQFVi653fYDYb UHz/ixtsILaoQJjEyukQU3kFBCV+TL4HZosA1dz5OB9sKLPAPKANc98DORwcwgI+EgtvsEIs a2SW2NDUwArSwCmgLbHl7TU2kBpmAT2J+xe1QMLMAvISm9e8ZZ7AKDALyYpZCFWzkFQtYGRe xSiaWpBcUJyUnmuoV5yYW1yal66XnJ+7iREcvc+kdjCubLA4xCjAwajEw3sjXj1UiDWxrLgy 9xCjBAezkgjv3xagEG9KYmVValF+fFFpTmrxIUZTYABMZJYSTc4HJpa8knhDYxMzI0sjc0ML I2NzJXHeObpyoUIC6YklqdmpqQWpRTB9TBycUg2MB5t3eVw6xMp1+Nmu9ZJxx4+qpGbY1iU1 5gV3qX4Q3PVXJ3ZToEf1rTy2u5/TZXh2sqh7z2up3T0xce5p8YrF/xLmtGp+/fMle24QJ9NB i9+aBzdpBAbv66nyajqfXmD381ouh7NqMiNHz8WiZ22TwjmStmwOri6ZovN8Q4To3obXzyb+ UvdRYinOSDTUYi4qTgQAPDJU4fQCAAA= DLP-Filter: Pass X-MTR: 20000000000000000@CPGS X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4196 Lines: 107 On 04/10/2015 05:46 PM, Robert Baldyga wrote: > On 04/10/2015 10:10 AM, Chanwoo Choi wrote: >> On 04/10/2015 04:45 PM, Robert Baldyga wrote: >>> 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 think this method is not proper to support this case. >> It may cause the confusion about other case using USB/USB-HOST cable state >> except of you commented case. > > That's why I finally proposed to use "USB-ID" and "USB-VBUS" in parallel > with old names. It seems to be simpler solution than adding new > mechanism notifying about VBUS and ID states changes. As I commented on previous reply, I don't agree to use 'USB-ID' and 'USB-VBUS'. If we add new strange 'USB-ID' and 'USB-VBUS' name, we would add non-general cable name continuoulsy. I think that extcon core provide the helper API to get the value of VBUS. But I need to consider it. > >> >>> >>>> 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? >> >> No, we need to consider more standard solution to support this case. >> > > 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/ > -- 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/