anchor.diff:                         mass-storage
                          endpt-num
                          endpt-in
  -                       #+nil
  -                       (mass-storage-semaphore mass-storage)
                          'mass-storage-int-callback)
       (if endpt-in
           (setf (mass-storage-bulk-in-endpt-num mass-storage) endpt-num)
  
positive.code:       (dotimes (i data-length)
          (setf (aref data-buf i) (aref buf (+ offset i))))
  
        (sync:semaphore-down (mass-storage-semaphore mass-storage))
  
        (with-trace-level (4)
          (sup:debug-print-line "%write-sector command status "
                                (mass-storage-status mass-storage)))
  
        (bulk-enqueue-buf usbd
                          device
                          (mass-storage-bulk-out-endpt-num mass-storage)
  
negative.code:         (sup:debug-print-line "inquiry command buffer:")
          (print-buffer sys.int::*cold-stream* cmd-buf :indent "  "))
  
        (when (eq (timed-wait event 1.0) :timeout)
          ;; TODO need better error message here
          (error "Mass storage inquiry command timeout"))
  
        (with-trace-level (4)
          (sup:debug-print-line "inquiry command status"
                                (mass-storage-status mass-storage)))
  
        (setf (sup:event-state event) nil)
        (bulk-enqueue-buf usbd
                          device
                          (mass-storage-bulk-in-endpt-num mass-storage)
                          data-buf
                          data-length)
  
        (when (eq (timed-wait event 1.0) :timeout)
          ;; TODO need better error message here
          (error "Mass storage inquiry data timeout"))
  
        (with-trace-level (3)
          (sup:debug-print-line "inquiry data buffer:")
  