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. > >> >>> 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. > Thanks, Robert Baldyga -- 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
