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. > >> 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. >> > > Ok, so do you have any idea how to do it? Do we want to supply > additional API for notifying about VBUS and ID changes? No, we need to consider more standard solution to support this case. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
