On Thu, May 08, 2014 at 10:25:46AM -0400, Alan Stern wrote: > On Thu, 8 May 2014, Zhuang Jin Can wrote: > > > > When the host already timed out the control transfer and started a new > > > one. Here's what I'm talking about: > > > > > > Host sends a Set-Configuration request. > > > > > > The UDC driver calls the gadget driver's setup function. > > > > > > The setup function returns DELAYED_STATUS. > > > > > > After a few seconds, the host gets tired of waiting and > > > sends a Get-Descriptor request > > My understanding is dwc3 will return NYET to host for this > > Get-Descriptor request transaction, as dwc3 is still in STATUS phase, > > there's no buffer to receive anything in ep0-out. > > dwc3 _cannot_ return NYET to a SETUP packet. The USB protocol does not > allow it. A device must always respond to SETUP with ACK. It true that device can not return NYET to a SETUP packet. A device must always respond to SETUP with ACK _if_ the SETUP packet is correctly received. Because there's no buffer prepared in ep0 for dwc3 to receive the SETUP packet, I guess there will be no handshake returned to host. I can confirm this by doing an experiment tomorrow:) Jincan -- 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
