From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754479AbbDJHRl (ORCPT ); Fri, 10 Apr 2015 03:17:41 -0400 Received: from mailout3.samsung.com ([203.254.224.33]:57317 "EHLO mailout3.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753588AbbDJHRj (ORCPT ); Fri, 10 Apr 2015 03:17:39 -0400 X-AuditID: cbfee690-f796f6d000005054-23-552779108cf6 Message-id: <55277910.2070000@samsung.com> Date: Fri, 10 Apr 2015 16:17:36 +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> In-reply-to: <55264534.4020006@samsung.com> Content-type: text/plain; charset=windows-1252 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprKIsWRmVeSWpSXmKPExsWyRsSkQFegUj3U4PwNc4v5R86xWlzeNYfN YtGyVmaLtUfuslvcblzBZvHg8E52i55HWg7sHn1bVjF6HL+xncnj8ya5AOYoLpuU1JzMstQi fbsEroyjUzwLLglUXPjr28A4ibeLkZNDQsBE4vmtb6wQtpjEhXvr2boYuTiEBJYySsx81cfc xcgBVnRxexREfDqjxNttV9khnAeMEhvOvmAH6eYV0JJYfO4uE4jNIqAqMWvnLGYQmw0ovv/F DTYQW1QgTGLl9CssEPWCEj8m3wOzRYBq7nycDzaUWWAeo8Tiue/ZQTYLC/hILLzBCrGskUli 7tZOsFM5BbQlWpbvYAWpYRbQk7h/UQskzCwgL7F5zVtmkHoJgV3sEmtXv2KBOEhA4tvkQywQ 38hKbDrADPGxpMTBFTdYJjCKzUJy0iyEqbOQTF3AyLyKUTS1ILmgOCm9yESvODG3uDQvXS85 P3cTIzC2Tv97NmEH470D1ocYBTgYlXh4G2LVQ4VYE8uKK3MPMZoCHTGRWUo0OR8YwXkl8YbG ZkYWpiamxkbmlmZK4ryvpX4GCwmkJ5akZqemFqQWxReV5qQWH2Jk4uCUamCcxatzoc47UrP0 o1decW/v2hXJUrN2ajYdEeBZcmNm0fv6LUufJMxj/aCmdoP7Zua+/IapjMc8HiVYd9//rHFc +2D3nX8bGjTPbHkk+nmy1sHdjxlvq1Z+aUtqqGBnXJD0gVv20+LZfp3uXx/+UXy7Zbnl3Gdr Qq0Pr/qh9EBw+ZX3wdozDovOU2Ipzkg01GIuKk4EALcPLB2oAgAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrPIsWRmVeSWpSXmKPExsVy+t9jQV2BSvVQg8lr9S3mHznHanF51xw2 i0XLWpkt1h65y25xu3EFm8WDwzvZLXoeaTmwe/RtWcXocfzGdiaPz5vkApijGhhtMlITU1KL FFLzkvNTMvPSbZW8g+Od403NDAx1DS0tzJUU8hJzU22VXHwCdN0yc4CWKymUJeaUAoUCEouL lfTtME0IDXHTtYBpjND1DQmC6zEyQAMJaxgzjk7xLLgkUHHhr28D4yTeLkYODgkBE4mL26O6 GDmBTDGJC/fWs3UxcnEICUxnlHi77So7hPOAUWLD2RfsIFW8AloSi8/dZQKxWQRUJWbtnMUM YrMBxfe/uMEGYosKhEmsnH6FBaJeUOLH5HtgtghQzZ2P88GGMgvMY5RYPPc9O8gVwgI+Egtv sEIsa2SSmLu1kxWkgVNAW6Jl+Q5WkBpmAT2J+xe1QMLMAvISm9e8ZZ7AKDALyYpZCFWzkFQt YGRexSiaWpBcUJyUnmukV5yYW1yal66XnJ+7iREcuc+kdzCuarA4xCjAwajEw9sQqx4qxJpY VlyZe4hRgoNZSYS3EiTEm5JYWZValB9fVJqTWnyI0RQYABOZpUST84FJJa8k3tDYxMzI0sjc 0MLI2FxJnHeOrlyokEB6YklqdmpqQWoRTB8TB6dUA2Nii+7b7h3Kjc+8/veeqnKXdC0XWF6h mimlWOF6oyo1nS3SkDngqXFgvxKT1r+syocpOfGpfr0beiv3zzO0vNNzy7Vzr8TK1ws5Pjof YWx4sqql6X7L58nlzpz/r8WvsZ8k7eluwPojWD+pd3dY5aVjFlyLXE/YsZn+XFjN8prP7O9j UeEAJZbijERDLeai4kQAMmzwQfICAAA= 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 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. 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. Thanks, Chanwoo Choi