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 that. As I wrote, current USB cable names are misleading. It would be better to have "USB-VBUS" and "USB-ID". >> In fact it would be better to have cables named "USB-VBUS" and "USB-ID" >> - in this convention it would be more clear. 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
