On Mon, Aug 11, 2014 at 09:35:46AM -0400, Alan Stern wrote: > On Mon, 11 Aug 2014, Peter Chen wrote: > > > > Hello Peter, > > > > > > I have seen this call is still returning EOPNOTSUPP which is also > > > returned by usb_gadget_connect and usb_gadget_disconnect if the pullup > > > function is not available. Should it not handle that case somehow special? > > > > > > > > > Is it still a valid condition to bailout if vbus is not active? > > > > > > > Hi Michael, > > > > I did this for possible pullup dp without connection (eg load gadget driver before > > vbus connect), it breaks USB spec, see 7.1.7.3 Connect and Disconnect Signaling at USB 2.0 spec. > > 7.1.7.3 doesn't say anything about enabling the D+ pullup before Vbus > is active. The closest it comes is the definition of Delta-t2 > (TSIGATT), but that is a _maximum_ time, not a _minimum_ time. > > What makes you think turning on the pullup when Vbus is off is bad? > > > I don't know what exactly problem you met, but current pullup dp during loading > > gadget driver behavior is not suitable for webcam and android use case even vbus > > is there. > > Why not? What's wrong with it? g_uvc needs a userspace counterpart. If we connect to the host before userspace is ready, we might connect as a non-usable function. -- balbi
Attachment:
signature.asc
Description: Digital signature
