From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763866AbdAFIuy (ORCPT ); Fri, 6 Jan 2017 03:50:54 -0500 Received: from mailout2.samsung.com ([203.254.224.25]:57420 "EHLO mailout2.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763846AbdAFIuu (ORCPT ); Fri, 6 Jan 2017 03:50:50 -0500 MIME-version: 1.0 Content-type: text/plain; charset=UTF-8 X-AuditID: b6c32a58-f79726d000001ac1-2b-586f5a62a364 Content-transfer-encoding: 8BIT Message-id: <586F5A62.8030704@samsung.com> Date: Fri, 06 Jan 2017 17:50:42 +0900 From: Chanwoo Choi Organization: Samsung Electronics User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 To: NeilBrown , cwchoi00@gmail.com, Baolin Wang Cc: "myungjoo.ham@samsung.com" , Mark Brown , linaro-kernel@lists.linaro.org, linux-kernel Subject: Re: [PATCH] extcon: Add documentation for EXTCON_CHG_USB_SLOW/FAST In-reply-to: <87y3yrn3y9.fsf@notabene.neil.brown.name> X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprBJsWRmVeSWpSXmKPExsWy7bCmum5SVH6EwZOfRhafGq4wW0x9+ITN 4tlRbYv3h54xW1zeNYfN4nbjCjaLTxtjHdg9ds66y+6xaVUnm8eda3vYPG7/e8zs0bdlFaPH +i1XWTw+b5ILYI9KtclITUxJLVJIzUvOT8nMS7dV8g6Od443NTMw1DW0tDBXUshLzE21VXLx CdB1y8wBOkdJoSwxpxQoFJBYXKykb2dTlF9akqqQkV9cYqsUbWhopGdoYK5nZGSkZ2Ica2Vk ClSSkJpxeeY19oLz4hU3n1Q1MC4U7mLk5JAQMJH4/ecSC4QtJnHh3nq2LkYuDiGBpYwSNw4d YAJJCAm0M0l8/VEK03Di+2kWiKI5jBJ7p69mB0nwCghK/Jh8DyjBwcEsIC9x5FI2SJhZQFNi 6+717BD19xgltjQ9Zwap4RXQkphx1B2khkVAVaJ9222wI9iAwvtf3GADsfkFFCWu/njMCGKL CkRI7Jz/jR2kVUQgSuLmGwWQkcwCqxklPh59zApSIyzgLdF8eQ+YzSlgJvHidiczSJGEwDF2 id4fl5hAmiUEZCU2HWCGMF0kbl91gXhLWOLV8S3sELa0xN+ltxghWiczSnSt/Qs1p4dRonHN UTaIKmOJ+w/uMUM8ySfR+/sJ1HxeiY42IYgSD4ltt85DlTtKTFn6jBkSDouZJKYsnss2gVFh FlLQzUIE3SykoFvAyLyKUSy1oDg3PbXYtMBErzgxt7g0L10vOT93EyM4VWpF7GD8NyPoEKMA B6MSD++NgPwIIdbEsuLK3EOMEhzMSiK8XYFAId6UxMqq1KL8+KLSnNTiQ4ymwKCfyCwlmpwP TON5JfGGJmaGJkaWQGhuaK4kzrugwjpCSCA9sSQ1OzW1ILUIpo+Jg1OqgdEpNkHaNKL4smHL rbLYLSb7Lyyr6rRePyn2Y+Jjj+T12guXnpjt+K86v/tyZULQB+VTUcHxU31ernFq+SFiF7Jp 7wV/6Qo3tQ27rnaXXAhpMH23yln4Ul5t4iEBfmNPG5GZ/d1/A1z6rIVfRf8KuSX1TXLG/4Sw tr+3JrDxli5+qOFY0jTtuhJLcUaioRZzUXEiAAOH47GrAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrGIsWRmVeSWpSXmKPExsVy+t9jQd2kqPwIg/8/lCw+NVxhtpj68Amb xbOj2hbvDz1jtri8aw6bxe3GFWwWnzbGOrB77Jx1l91j06pONo871/awedz+95jZo2/LKkaP 9Vuusnh83iQXwB7lZpORmpiSWqSQmpecn5KZl26rFBripmuhpJCXmJtqqxSh6xsSpKRQlphT CuQZGaABB+cA92AlfbsEt4zLM6+xF5wXr7j5pKqBcaFwFyMnh4SAicSJ76dZIGwxiQv31rN1 MXJxCAnMYpS4P/UxM0iCV0BQ4sfke0BFHBzMAvISRy5lg4SZBdQlJs1bxAxR/4BRoufYNCaQ Gl4BLYkZR91BalgEVCXat90Gm88GFN7/4gYbiM0voChx9cdjRpByUYEIie4TlSBhEYEoiTkN IOdwAY1fzShx4etuVpCEsIC3RPPlPawQu5YySTzfNhlsKKeAmcSL253MExgFZyE5dRbCqbOQ nLqAkXkVo0RqQXJBcVJ6rlFearlecWJucWleul5yfu4mRnAcPpPewXh4l/shRgEORiUe3giv vAgh1sSy4srcQ4wSHMxKIrxdgfkRQrwpiZVVqUX58UWlOanFhxhNgZ6dyCwlmpwPTBF5JfGG JuYm5sYGFuaWliZGSuK8jbOfhQsJpCeWpGanphakFsH0MXFwSjUwHu1+NKnqjN/JdDldhS1P q8TSzvB6qfHu3LqIn9d5eX4t3/V/CdtTT8zxfG7zvn7Xv2K/LRJnDn65ELoib4L2/V+fvoUu vrRigVu+7C/rWtn5x2TmPi9QyCnr+SX36dnmwEe2ulzx60SteeOZD3s8vX5S0U6psPCLYXau 6/RLBZN4f+x3XOoZpsRSnJFoqMVcVJwIAK4MjTPZAgAA X-MTR: 20000000000000000@CPGS X-CMS-MailID: 20170106085042epcas5p381e6088c4fd5d7ef2990e3894960636a X-Msg-Generator: CA X-Sender-IP: 203.254.230.27 X-Local-Sender: =?UTF-8?B?7LWc7LCs7JqwG1RpemVuIFBsYXRmb3JtIExhYihTL1fshLw=?= =?UTF-8?B?7YSwKRvsgrzshLHsoITsnpAbUzUo7LGF7J6EKS9DaGFuZ2UgQWdlbnQ=?= X-Global-Sender: =?UTF-8?B?Q2hhbndvbyBDaG9pG1RpemVuIFBsYXRmb3JtIExhYi4bU2Ft?= =?UTF-8?B?c3VuZyBFbGVjdHJvbmljcxtTNS9TZW5pb3IgRW5naW5lZXI=?= X-Sender-Code: =?UTF-8?B?QzEwG1NUQUYbQzEwVjgxMTE=?= CMS-TYPE: 105P DLP-Filter: Pass X-CFilter-Loop: Reflected X-HopCount: 7 X-CMS-RootMailID: 20170103230158epcas2p1375e47a387725069f5f35084fb383f05 X-RootMTR: 20170103230158epcas2p1375e47a387725069f5f35084fb383f05 References: <87y3yrn3y9.fsf@notabene.neil.brown.name> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi NeilBrown, On 2017년 01월 04일 08:01, NeilBrown wrote: > On Tue, Jan 03 2017, Chanwoo Choi wrote: > >> Hi Baolin, >> >> 2017-01-03 14:50 GMT+09:00 Baolin Wang : >>> Currently there are no documentation for EXTCON_CHG_USB_SLOW/FAST >>> charger connector. These names don't mean much and no guide to tell >>> users how to use it, thus try to add documentation to make them clear. >>> >>> Suggested-by: NeilBrown >>> Signed-off-by: Baolin Wang >>> --- >>> include/linux/extcon.h | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git a/include/linux/extcon.h b/include/linux/extcon.h >>> index 0020123..ceec1f0 100644 >>> --- a/include/linux/extcon.h >>> +++ b/include/linux/extcon.h >>> @@ -53,6 +53,10 @@ >>> * the USB connector, which means EXTCON_CHG_USB_SDP should always >>> * appear together with EXTCON_USB. The same as ACA charger connector, >>> * EXTCON_CHG_USB_ACA would normally appear with EXTCON_USB_HOST. >>> + * >>> + * A cable of type EXTCON_CHG_USB_SLOW can provide at least 500mA of >>> + * current at 5V. A cable of type EXTCON_CHG_USB_FAST can provide at >>> + * least 1A of current at 5V. >> >> I agree the at least current value(mA) for EXTCON_CHG_USB_SLOW/FAST. >> But, I'm worried that fix the 5V. >> >> I have a plan to support the 'current' and 'voltage' property for >> charger connector as following: >> - EXTCON_PROP_CHG_CURRNET >> - EXTCON_PROP_CHG_VOLTAGE >> >> So, I don't like to fix the voltage for EXTCON_CHG_USB_SLOW/FAST. >> How about this? > > I think you should be very caution about pursuing this approach. As it > stands, it implies that a given cable has a fixed voltage and a fixed > available current. This is not true of many cables. > > The USB battery charging spec defines a range of possibly current limits > that each cable type can provide. There is a defined protocol for the > slave to detect how much current is available within that range. So > setting a single "CHG_CURRENT" property would be incorrect. > > For SDP ports, the current limit is negotiation using the USB protocol > and it is completely unknown to the cable (and so to EXTCON). For > USB-C, there is a greater range of voltages and currents. I don't know > the details, but I do know that a single-valued "PROP_CHG_VOLTAGE" would > not be appropriate. > > I think that EXTCON should stick with identifying the type of cable, and > leave it to the client to determine what other properties are implied by > each particular cable type. First of all, Thanks for your detailed comment. The power-supply already has the voltage/current property for power-supply device as following: - POWER_SUPPLY_PROP_CONSTANT_CHARGE_CURRENT - POWER_SUPPLY_PROP_CONSTANT_CHARGE_CURRENT_MAX - POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE - POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE_MAX -- Best Regards, Chanwoo Choi S/W Center, Samsung Electronics