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. > >> >>> >>>> 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-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- 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
