Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754151AbbDJHjo (ORCPT ); Fri, 10 Apr 2015 03:39:44 -0400 Received: from mailout3.samsung.com ([203.254.224.33]:62810 "EHLO mailout3.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752975AbbDJHjl (ORCPT ); Fri, 10 Apr 2015 03:39:41 -0400 X-AuditID: cbfee68f-f793b6d000005f66-bc-55277e392be4 Message-id: <55277E39.1020806@samsung.com> Date: Fri, 10 Apr 2015 16:39:37 +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: Roger Quadros Cc: Robert Baldyga , myungjoo.ham@samsung.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> <55264D8B.7010301@ti.com> In-reply-to: <55264D8B.7010301@ti.com> Content-type: text/plain; charset=windows-1252 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprOIsWRmVeSWpSXmKPExsWyRsSkWNeyTj3U4P8qMYv5R86xWlzeNYfN YtGyVmaLtUfuslvcblzBZvHg8E52i55HWg7sHn1bVjF6HL+xncnj8ya5AOYoLpuU1JzMstQi fbsEroxJ1/4wFbzkr7jc+Zm5gXEvTxcjJ4eEgInE6bs3GCFsMYkL99azdTFycQgJLGWUeL1g ElMXIwdYUdeXUoj4IkaJd9f6mSCcB4wSG5a8YQHp5hXQkni+7DUbiM0ioCqx4d5WMJsNKL7/ xQ0wW1QgTGLl9CtQ9YISPybfA7NFBBQl7q2E2MwssJ1RonP5dVaQzcICPhILb7BCLJvLJLFt exPYqZwCahInDzwHq2EW0JO4f1ELJMwsIC+xec1bZpB6CYFt7BLL/72FOkhA4tvkQywQ38hK bDrADPGxpMTBFTdYJjCKzUJy0iyEqbOQTF3AyLyKUTS1ILmgOCm9yFivODG3uDQvXS85P3cT IzC+Tv971r+D8e4B60OMAhyMSjy8DbHqoUKsiWXFlbmHGE2BjpjILCWanA+M4rySeENjMyML UxNTYyNzSzMlcd6FUj+DhQTSE0tSs1NTC1KL4otKc1KLDzEycXBKNTBqz1oc4NR5SCXlr9+2 a5ytEdMVHs7YqWw5U+tFRdO5ewIKJkLxQsk/ZVf8CcxcIRQgoLty42qxG3zfi58eOBrorPFD ouCwrrB0xDbbh/vvWmcf6l8d9+iLldGFJisH0Yg+ma72zsk7eJj8l85afypE6M33+5xeM+yc dn3V+Bk6NWRnv4WGQI4SS3FGoqEWc1FxIgDL5PXFqgIAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrIIsWRmVeSWpSXmKPExsVy+t9jAV3LOvVQg5dd/Bbzj5xjtbi8aw6b xaJlrcwWa4/cZbe43biCzeLB4Z3sFj2PtBzYPfq2rGL0OH5jO5PH501yAcxRDYw2GamJKalF Cql5yfkpmXnptkrewfHO8aZmBoa6hpYW5koKeYm5qbZKLj4Bum6ZOUDLlRTKEnNKgUIBicXF Svp2mCaEhrjpWsA0Ruj6hgTB9RgZoIGENYwZk679YSp4yV9xufMzcwPjXp4uRg4OCQETia4v pV2MnECmmMSFe+vZuhi5OIQEFjFKvLvWzwThPGCU2LDkDQtIFa+AlsTzZa/ZQGwWAVWJDfe2 gtlsQPH9L26A2aICYRIrp1+BqheU+DH5HpgtIqAocW8lxAZmge2MEp3Lr7OCXCEs4COx8AYr xLK5TBLbtjcxgjRwCqhJnDzwHKyGWUBP4v5FLZAws4C8xOY1b5knMArMQrJiFkLVLCRVCxiZ VzGKphYkFxQnpeca6RUn5haX5qXrJefnbmIER+8z6R2MqxosDjEKcDAq8fA2xKqHCrEmlhVX 5h5ilOBgVhLhrQQJ8aYkVlalFuXHF5XmpBYfYjQFBsBEZinR5HxgYskriTc0NjEzsjQyN7Qw MjZXEuedoysXKiSQnliSmp2aWpBaBNPHxMEp1cCY++Ca88mop6s1j2T75eWVxm7R+MLZ9f69 Bo+2+WqdJzxSThdkz/OW9E8Xsg1nzYk53btLqVZDMs+49Y2G0cT/LK7HTXTP7Uw/v9n7ovpJ iacaDDyz4qf2cxlrJnxh8QsOzD+8wE3h/KeXEktZi4J56pdYGH+f72FTFescU8lw6bXZGxux uUosxRmJhlrMRcWJAOzdtHH0AgAA 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: 2209 Lines: 66 Hi Roger, On 04/09/2015 06:59 PM, Roger Quadros wrote: > Hi, > > On 09/04/15 12:24, 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. > > At least for the kernel users [1] we are treating USB-HOST as !ID and USB as VBUS. > So it is not an issue for these kernel users if both USB and USB-HOST are attached. > This is a valid USB state. This case is only valid kernel users[1]. I think that we must consider all case about extcon consumer driver and some framework. > If we don't do so then extcon with 3 cable states is not sufficient to capture the > entire USB scenario. (we need 4 states for 2 pins). > > [1] > - drivers/usb/phy/phy-omap-otg.c > - drivers/usb/dwc3/dwc3-omap.c > I think that extcon-usb-gpio.c send the only attached state of USB-HOST and extcon could provider VBUS state with other solution instead of sending the attached state of both USB and USB-HOST cable at the same time. Thanks, Chanwoo Choi -- 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/