Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932541AbbDOJ0a (ORCPT ); Wed, 15 Apr 2015 05:26:30 -0400 Received: from mailout2.samsung.com ([203.254.224.25]:56174 "EHLO mailout2.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755498AbbDOJ00 (ORCPT ); Wed, 15 Apr 2015 05:26:26 -0400 X-AuditID: cbfee68e-f79c56d000006efb-59-552e2ec0ac33 Message-id: <552E2EBF.5090906@samsung.com> Date: Wed, 15 Apr 2015 18:26:23 +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: Peter Chen , Robert Baldyga , myungjoo.ham@samsung.com, linux-usb@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, m.szyprowski@samsung.com, "Balbi, Felipe" , "ABRAHAM, KISHON VIJAY" Subject: Re: [PATCH v3 2/4] extcon: usb-gpio: add support for VBUS detection References: <55277910.2070000@samsung.com> <55277FA2.6090700@samsung.com> <55278580.2090809@samsung.com> <55278DD3.3020409@samsung.com> <55279550.1060609@samsung.com> <552CE579.6060702@ti.com> <552CE5C0.3010207@ti.com> <552CEC97.1050205@samsung.com> <552CEE42.1050907@ti.com> <552CFA1E.5070400@samsung.com> <20150415032734.GA29095@shlinux2> <552E1862.6090709@ti.com> In-reply-to: <552E1862.6090709@ti.com> Content-type: text/plain; charset=windows-1252 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrJIsWRmVeSWpSXmKPExsWyRsSkSPeAnl6owffrXBYH79dbzD9yjtXi wtMeNovLu+awWSxa1spssfbIXXaL240r2CyOzf7LZPHg8E52i55HWg5cHv8O9zN59G1Zxehx /MZ2Jo/Pm+QCWKK4bFJSczLLUov07RK4Mo41tzMXLPGsOHT/EHMDY4dNFyMnh4SAicT0z2uY IWwxiQv31rN1MXJxCAksZZS4cuk4C0zR/2X72SES0xkllt6dwgjhPGCUuLz8OlAVBwevgJbE 860hIA0sAqoSu88/Zwex2YDC+1/cYAOxRQXCJFZOvwI2lFdAUOLH5HtgtoiAosS9lRCbmQVW M0m861zKCjJTWMBHYuENVohdP5gkNh1sZQaJcwqoSRzv8QQxmQX0JO5f1AIZwywgL7F5zVtm kHIJgVvsEgfnfmKHuEdA4tvkQ2BnSgjISmw6APWwpMTBFTdYJjCKzUJy0SyEqbOQTF3AyLyK UTS1ILmgOCm9yEivODG3uDQvXS85P3cTIzAGT/971reD8eYB60OMAhyMSjy8CxfohgqxJpYV V+YeYjQFOmIis5Rocj4w0vNK4g2NzYwsTE1MjY3MLc2UxHkTpH4GCwmkJ5akZqemFqQWxReV 5qQWH2Jk4uCUamAU0HnzZInK+/PX1hv5Tnt9vG69M8u//t5l4RcyKjtX8qRa3jCTYbf4Ehof dbnEx6gyuYS9P6HQ+PCar7cXxbH6y7M9ZOC7rBA+3fVyALvb2z+5z86a6m1cJcaQY7/lMd8F KSahueunmu7Y18yQaXBWnic3UGbF82WOy8653NLWP/hWuPK13AYlluKMREMt5qLiRABvrz8q vAIAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrMIsWRmVeSWpSXmKPExsVy+t9jQd39enqhBg2zVSwO3q+3mH/kHKvF hac9bBaXd81hs1i0rJXZYu2Ru+wWtxtXsFkcm/2XyeLB4Z3sFj2PtBy4PP4d7mfy6NuyitHj +I3tTB6fN8kFsEQ1MNpkpCampBYppOYl56dk5qXbKnkHxzvHm5oZGOoaWlqYKynkJeam2iq5 +AToumXmAN2jpFCWmFMKFApILC5W0rfDNCE0xE3XAqYxQtc3JAiux8gADSSsYcw41tzOXLDE s+LQ/UPMDYwdNl2MnBwSAiYS/5ftZ4ewxSQu3FvP1sXIxSEkMJ1RYundKYwQzgNGicvLr7N0 MXJw8ApoSTzfGgLSwCKgKrH7/HOwZjag8P4XN9hAbFGBMImV06+wgNi8AoISPybfA7NFBBQl 7q2EWMAssJpJ4l3nUlaQmcICPhILb7BC7PrBJLHpYCszSJxTQE3ieI8niMksoCdx/6IWyBhm AXmJzWveMk9gFJiFZMMshKpZSKoWMDKvYhRNLUguKE5KzzXSK07MLS7NS9dLzs/dxAiO8GfS OxhXNVgcYhTgYFTi4V2wQDdUiDWxrLgy9xCjBAezkghvsqZeqBBvSmJlVWpRfnxRaU5q8SFG U6D/JzJLiSbnA5NPXkm8obGJmZGlkbmhhZGxuZI47xxduVAhgfTEktTs1NSC1CKYPiYOTqkG RjazCUkMLzXmpHZxhB3PW/v5qo6UAAsLZ2W8dvw+43fvRJQsGGrk/891m8mcz3t+Dd/rJEmV PO2FMnbBi332r964zdGSWVVln/drLb/FSeI8N/6bxqgK92i9NX/+I6xptngXv86NuL7VPAGP +CYFRqyTar1pb7Ffq39pTF7Y9J7a/147Lj1VYinOSDTUYi4qTgQAuvlyUwYDAAA= 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: 9423 Lines: 207 Hi Roger and Peter, On 04/15/2015 04:50 PM, Roger Quadros wrote: > On 15/04/15 06:27, Peter Chen wrote: >> On Tue, Apr 14, 2015 at 08:29:34PM +0900, Chanwoo Choi wrote: >>> On 04/14/2015 07:38 PM, Roger Quadros wrote: >>>> On 14/04/15 13:31, Chanwoo Choi wrote: >>>>> On 04/14/2015 07:02 PM, Roger Quadros wrote: >>>>>> Fixed Kishon's id. >>>>>> >>>>>> On 14/04/15 13:01, Roger Quadros wrote: >>>>>>> On 10/04/15 12:18, Chanwoo Choi wrote: >>>>>>>> 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. >>>>>>> >>>>>>> Now it is starting to look like existing extcon states are not suitable for USB/PHY drivers to deliver >>>>>>> VBUS and ID information reliably. >>>>>>> This is because based on your comments the "USB" and "USB-HOST" states look like some fuzzy states >>>>>>> and have no direct correspondence with "VBUS" and "ID". The fact that they can't become >>>>>>> attached simultaneously makes me conclude that "USB" and "USB-HOST" cable states are really >>>>>>> capturing only the ID pin state. >>>>>>> >>>>>>> I can suggest the following options >>>>>>> a) let "USB" and "USB-HOST" only indicate ID pin status. Add a new cable state for "VBUS" notification. >>>>>>> Maybe call it "USB-POWER" or something. >>>>> >>>>> We must discuss it before using the new cable name >>>>> such as "USB-POWER", "USB-ID" and "USB-VBUS". >>>> >>>> I didn't say to add "USB-ID" or "USB-VBUS". solution (a) was to have the following >>> >>> Right. Robert suggested the "USB-ID" and "USB-VBUS" cable name on previous mail in mail thread. >> >> From USB/USB-PHY driver point, it needs to know id and vbus value >> for their internal logic, so as extcon users, the cable name >> is better to reflect meaning of id and vbus, like "USB-ID" and "USB-VBUS", >> if the power is from vbus pin at USB cable, I don't think we need another >> cable name "USB-POWER" even the USB/USB-PHY driver don't need it. > > I agree as well that this is the *best* option for USB case. Just because Chanwoo was > objecting these names I suggested "USB-POWER". > > Chanwoo, can we simply get rid of "USB" and "USB-HOST" cables and move to > "USB-ID" and "USB-VBUS"? I'm wondering about changing the previous cable name from 'USB'/'USB-HOST' to 'USB-ID/USB-VBUS' because extcon framework update the state of cable by using uevent and the user-space process would catch the changed state by using cable name ('USB'/'USB-HOST'). The user-space process may not consider the both id and vbus of USB. If 'USB-ID'/'USB-VBUS' cable name is used instead of 'USB'/'USB-HOST', It may cause the confusion about what is meaning of cable name on user-space process. So, I prefer to use existing 'USB' and 'USB-HOST' cable name. and then want to add additional method to get the vbus state. I think two following method to get the vbus state. 1) Add the extcon_{get|set}_vbus_state() - extcon_{get|set}_vbus_state() - the list of of return value #define EXTCON_USB_VBUS_OFF 0 #define EXTCON_USB_VBUS_ON 1 When USB/USB-HOST is attached and receive the notification onextcon consumer driver ,extcon consumer driver would get the vbus state by extcon_get_vbus_state(). 2) Add the notifier chain for vbus state update - extcon_{register|unregister}_vbus_notifier() - the list of notifier event #define EXTCON_USB_VBUS_OFF 0 #define EXTCON_USB_VBUS_ON 1 3) add the new cable 'USB-POWER' by Roger suggestion . - When 'USB-POWER' cable is attached, extcon will update the cable state 'USB-POWER' means only the vbus state. But, 'USB-POWER' is not h/w cable. The user-space process would handle this uevent of 'USB-POWER' such as h/w cable's uevent. I think it is not clear on the user-space process aspect. > > The only reason you objected was saying that it is a strange cable name. Well this is > only what we care about from USB PHY drivers and user space is not interested in it > so what is the concern? I added the reason why don't want to change the legacy cable name about USB/USB-HOST. > >> >>> >>>> "USB" - attached means ID is high. i.e. Type-B plug attached. >>>> "USB-HOST" - attached means ID is low. i.e. Type-A plug attached. >>>> "USB-POWER" - attached means USB power is present. i.e. VBUS is alive. >>>> >>>> This way the definition of USB and USB-HOST remain true to their name and avoid further confusions. >>>> VBUS state is got through the "USB-POWER" cable state. >>> >>> There is the same case for MHL cable. >>> Also, MHL cable could be connected to VBUS line. >>> - MHL : attached just MHL cable. >>> - MHL-POWER : attache MHL cable which is connected with VBUS line. >>> >>> We must need the opinion of USB/PHY driver's maintainer. >>> >>>> >>>>> >>>>> What is the appropriate method of following two solution? >>>>> - Fisrt, use the new cable name "USB-*". >>>> I explained this above. >>>> >>>>> - Second, use the additional API to get the VBUS state. >>>> >>>> You keep mentioning additional API for VBUS. But I don't see any such API. Can you please >>>> suggest what API you are talking about? >>> >>> I'm considering following functions for VBUS state. But it is my opinion, >>> If USB/PHY drivers's maintainers don't agree the new cable ("USB-POWER"), >>> We could use the following function to get VBUS state. >>> Because new cable name will affect the USB/PHY drivers. >>> - int extcon_{get|set}_vbus_state(struct extcon_dev *edev); > > This is not suitable for us as USB drivers need VBUS notification event to come. > They can't keep polling for VBUS state using this API. I don't agree the polling method. You refer to upper my description. 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/