Man page 9 : usb_bus_start_enum

usb_bus_start_enum - start immediate enumeration (for OTG)

int usb_bus_start_enum(struct usb_bus *  bus , unsigned  port_num );

bus
    the bus (must use hcd framework)

port_num
    1-based number of port; usually bus->otg_port

in_interrupt

Starts enumeration, with an immediate reset followed later by khubd identifying and possibly configuring the device. This is needed by OTG controller drivers, where it helps meet HNP protocol timing requirements for starting a port reset.