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 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? 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
