anchor.diff:  ;; success responses
   (defconstant +virtio-gpu-resp-ok-nodata+               #x1100)
   (defconstant +virtio-gpu-resp-ok-display-info+         #x1101)
  +(defconstant +virtio-gpu-resp-ok-capset-info+          #x1102)
  +(defconstant +virtio-gpu-resp-ok-capset+               #x1103)
   
   ;; error responses
   (defconstant +virtio-gpu-resp-err-unspec+              #x1200)
  
positive.code:     ;; Set the driver bit in the status field.
      (setf (virtio-device-status device) (logior +virtio-status-acknowledge+
                                                  +virtio-status-driver+))
      ;; Allocate virtqueues.
      (when (not (virtio-configure-virtqueues device 2))
        (setf (virtio-device-status device) +virtio-status-failed+)
        (return-from virtio-gpu-register nil))
      (when (virtio-device-feature device +virtio-gpu-f-virgl+)
        (setf (virtio-driver-feature device +virtio-gpu-f-virgl+) t)
        (debug-print-line "virtio-gpu: virgl enabled"))
      ;; Configuration complete, go to OK mode.
      (setf (virtio-device-status device) (logior +virtio-status-acknowledge+
                                                  +virtio-status-driver+
  
negative.code: (defconstant +virtio-gpu-format-a8b8g8r8-unorm+ 121)
  (defconstant +virtio-gpu-format-r8g8b8x8-unorm+ 134)
  
  (defconstant +virtio-gpu-update-cursor-scanout-id+ 0)
  (defconstant +virtio-gpu-update-cursor-x+ 4)
  (defconstant +virtio-gpu-update-cursor-y+ 8)
  