anchor.diff:                         (usb-device-max-packet device))
          (ed-tdq-tail ed) td-phys-addr
          (ed-tdq-head ed) td-phys-addr
  -       ;; Add mapping from "dummy" td to endpoint
  -       (gethash td (td->endpoint ohci)) endpoint)
  +       ;; Add mapping from "dummy" td to td-info
  +       (gethash td (td->td-info ohci)) (make-td-info
  +                                        :event-type event-type
  +                                        :endpoint endpoint
  +                                        :buf-size buf-size))
   
         (dotimes (i num-bufs)
  -        ;; Add mapping from each new "dummy" td to endpoint
  -        (setf (gethash (add-td ohci ed td-header buf-size) (td->endpoint ohci))
  -              endpoint))
  +        ;; Add mapping from each new "dummy" td to td-info
  +        (let ((dummy-td (add-td ohci ed td-header buf-size)))
  +          (setf (gethash dummy-td  (td->td-info ohci))
  +                (make-td-info :event-type event-type
  +                              :endpoint endpoint
  +                              :buf-size buf-size))))
         (add-interrupt-ed ohci ed buf-size interval)
         endpt-num)))
   
  
positive.code:     (if (= buf-pointer 0) buf-size (- buf-pointer buf-start))))
  
  ;;======================================================================
  ;; HCCA (Host Controller Communication Area) - defined in section 4.4
  ;;======================================================================
  
  
negative.code:        buf
         dummy-td)
  
        (setf (td-info-buf-size td-info) length
              (td-info-buf td-info) buf
              (gethash msg-td (td->td-info ohci)) td-info
              (ed-tdq-tail ed) (array->phys-addr dummy-td))
  
        (with-trace-level (3)
  