On 04/10/2015 11:18 AM, 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. We need more than API for getting VBUS value - we need to be notified about its changes, because if we don't distinguish between USB-HOST with VBUS on, and USB-HOST with VBUS off, then we will not receive notification from extcon at VBUS state change. Thanks, Robert Baldyga -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
