On Wed, Aug 3, 2016 at 5:42 PM, Chanwoo Choi <cw00.c...@samsung.com> wrote: > Hi Roger, > > On 2016년 08월 03일 18:46, Roger Quadros wrote: >> Hi Chanwoo, >>
[ ... ] >>>>> + /* >>>>> + * Check whether the external connector is attached. >>>>> + * If external connector is detached, the user can not >>>>> + * get the property value. >>>>> + */ >>>> >>>> How will this work for USB case? We need to know VBUS and ID states >>>> even if the USB cable is detached. >>> >>> When USB is detached, extcon_get_property return the default value without >>> any operation. >>> The default value of supported property are 0 (zero). If new property need >>> the differnt default >>> value, I'll support it. >> >> Is the property a property of the connector or of the cable? >> >> In my opinion, ID and VBUS are properties of the USB connector and not of >> the USB cable. So extcon must provide valid status for those properties >> even if USB cable or USB_HOST cable is detached. > > I don't understand about that if USB and USB_HOST are detached, > how can the USB be operating? As you mentioned that, extcon must > provide the valid status for both state and properties. > Correct. No cable means that the polarity is unknown, and VBUS must not be active (for USB_HOST), or it can not be active (for USB). Only question might be EXTCON_PROP_USB_ID; I am not sure I understand what it is supposed to return. Maybe it would be worthwhile to document it ? > So, I already mentioned, When USB and USB_HOST are detached, > extcon return the default value instead of error value. > I think that it is reasonable. Why is it not a valid? > I agree; I don't know what else could be returned if no cable is attached, even if we wanted to. Guenter
