Index: /trunk/src/VBox/Devices/Input/PS2M.cpp
===================================================================
--- /trunk/src/VBox/Devices/Input/PS2M.cpp	(revision 50805)
+++ /trunk/src/VBox/Devices/Input/PS2M.cpp	(revision 50806)
@@ -48,7 +48,7 @@
  * sequence can be used to switch to ImPS/2 or ImEx mode. Three consecutive
  * Set Sampling Rate (0F3h) commands with arguments 200, 100, 80 switch to ImPS/2
- * mode. While in ImPS/2 mode, three consecutive Set Sampling Rate commands with
- * arguments 200, 200, 80 switch to ImEx mode. The Read ID (0F2h) command will
- * report the currently selected protocol.
+ * mode. While in ImPS/2 or PS/2 mode, three consecutive Set Sampling Rate
+ * commands with arguments 200, 200, 80 switch to ImEx mode. The Read ID (0F2h)
+ * command will report the currently selected protocol.
  *
  *
@@ -197,7 +197,6 @@
 typedef enum {
     PS2M_KNOCK_INITIAL,
-    PS2M_KNOCK_IMPS2_1ST,
+    PS2M_KNOCK_1ST,
     PS2M_KNOCK_IMPS2_2ND,
-    PS2M_KNOCK_IMEX_1ST,
     PS2M_KNOCK_IMEX_2ND
 } PS2M_KNOCK_STATE;
@@ -459,51 +458,35 @@
 static void ps2mRateProtocolKnock(PPS2M pThis, uint8_t rate)
 {
-    if (pThis->enmProtocol == PS2M_PROTO_PS2STD)
-    {
-        switch (pThis->enmKnockState)
+    switch (pThis->enmKnockState)
+    {
+    case PS2M_KNOCK_INITIAL:
+        if (rate == 200)
+            pThis->enmKnockState = PS2M_KNOCK_1ST;
+        break;
+    case PS2M_KNOCK_1ST:
+        if (rate == 100)
+            pThis->enmKnockState = PS2M_KNOCK_IMPS2_2ND;
+        else if (rate == 200)
+            pThis->enmKnockState = PS2M_KNOCK_IMEX_2ND;
+        else
+            pThis->enmKnockState = PS2M_KNOCK_INITIAL;
+        break;
+    case PS2M_KNOCK_IMPS2_2ND:
+        if (rate == 80)
         {
-        case PS2M_KNOCK_INITIAL:
-            if (rate == 200)
-                pThis->enmKnockState = PS2M_KNOCK_IMPS2_1ST;
-            break;
-        case PS2M_KNOCK_IMPS2_1ST:
-            if (rate == 100)
-                pThis->enmKnockState = PS2M_KNOCK_IMPS2_2ND;
-            else
-                pThis->enmKnockState = PS2M_KNOCK_INITIAL;
-            break;
-        case PS2M_KNOCK_IMPS2_2ND:
-            if (rate == 80)
-            {
-                pThis->enmProtocol = PS2M_PROTO_IMPS2;
-                LogRelFlow(("PS2M: Switching mouse to ImPS/2 protocol.\n"));
-            }
-        default:
-            pThis->enmKnockState = PS2M_KNOCK_INITIAL;
+            pThis->enmProtocol = PS2M_PROTO_IMPS2;
+            LogRelFlow(("PS2M: Switching mouse to ImPS/2 protocol.\n"));
         }
-    }
-    else if (pThis->enmProtocol == PS2M_PROTO_IMPS2)
-    {
-        switch (pThis->enmKnockState)
+        pThis->enmKnockState = PS2M_KNOCK_INITIAL;
+        break;
+    case PS2M_KNOCK_IMEX_2ND:
+        if (rate == 80)
         {
-        case PS2M_KNOCK_INITIAL:
-            if (rate == 200)
-                pThis->enmKnockState = PS2M_KNOCK_IMEX_1ST;
-            break;
-        case PS2M_KNOCK_IMEX_1ST:
-            if (rate == 200)
-                pThis->enmKnockState = PS2M_KNOCK_IMEX_2ND;
-            else
-                pThis->enmKnockState = PS2M_KNOCK_INITIAL;
-            break;
-        case PS2M_KNOCK_IMEX_2ND:
-            if (rate == 80)
-            {
-                pThis->enmProtocol = PS2M_PROTO_IMEX;
-                LogRelFlow(("PS2M: Switching mouse to ImEx protocol.\n"));
-            }
-        default:
-            pThis->enmKnockState = PS2M_KNOCK_INITIAL;
+            pThis->enmProtocol = PS2M_PROTO_IMEX;
+            LogRelFlow(("PS2M: Switching mouse to ImEx protocol.\n"));
         }
+        /* Fall through! */
+    default:
+        pThis->enmKnockState = PS2M_KNOCK_INITIAL;
     }
 }