hcd
urb
status
This hands the URB from HCD to its USB device driver, using its completion function. The HCD has freed all per-urb resources (and is done using urb->hcpriv). It also released all HCD locks; the device driver won't cause problems if it frees, modifies, or resubmits this URB.
If urb was unlinked, the value of status will be overridden by urb->unlinked. Erroneous short transfers are detected in case the HCD hasn't checked for them.