Index: /trunk/include/VBox/vmm/pdmusb.h
===================================================================
--- /trunk/include/VBox/vmm/pdmusb.h	(revision 51289)
+++ /trunk/include/VBox/vmm/pdmusb.h	(revision 51290)
@@ -4,5 +4,5 @@
 
 /*
- * Copyright (C) 2006-2013 Oracle Corporation
+ * Copyright (C) 2006-2014 Oracle Corporation
  *
  * This file is part of VirtualBox Open Source Edition (OSE), as
@@ -451,5 +451,5 @@
      * Attaches a driver (chain) to the USB device.
      *
-     * The first call for a LUN this will serve as a registartion of the LUN. The pBaseInterface and
+     * The first call for a LUN this will serve as a registration of the LUN. The pBaseInterface and
      * the pszDesc string will be registered with that LUN and kept around for PDMR3QueryUSBDeviceLun().
      *
@@ -1067,4 +1067,5 @@
 VMMR3DECL(int)  PDMR3UsbDriverDetach(PUVM pUVM, const char *pszDevice, unsigned iDevIns, unsigned iLun,
                                      const char *pszDriver, unsigned iOccurance, uint32_t fFlags);
+VMMR3DECL(int)  PDMR3UsbQueryLun(PUVM pUVM, const char *pszDevice, unsigned iInstance, unsigned iLun, PPDMIBASE *ppBase);
 
 /** @} */
Index: /trunk/src/VBox/VMM/VMMR3/PDMUsb.cpp
===================================================================
--- /trunk/src/VBox/VMM/VMMR3/PDMUsb.cpp	(revision 51289)
+++ /trunk/src/VBox/VMM/VMMR3/PDMUsb.cpp	(revision 51290)
@@ -5,5 +5,5 @@
 
 /*
- * Copyright (C) 2006-2013 Oracle Corporation
+ * Copyright (C) 2006-2014 Oracle Corporation
  *
  * This file is part of VirtualBox Open Source Edition (OSE), as
@@ -1394,4 +1394,44 @@
 
     LogFlow(("PDMR3UsbDriverDetach: returns %Rrc\n", rc));
+    return rc;
+}
+
+
+/**
+ * Query the interface of the top level driver on a LUN.
+ *
+ * @returns VBox status code.
+ * @param   pUVM            The user mode VM handle.
+ * @param   pszDevice       Device name.
+ * @param   iInstance       Device instance.
+ * @param   iLun            The Logical Unit to obtain the interface of.
+ * @param   ppBase          Where to store the base interface pointer.
+ * @remark  We're not doing any locking ATM, so don't try call this at times when the
+ *          device chain is known to be updated.
+ */
+VMMR3DECL(int)  PDMR3UsbQueryLun(PUVM pUVM, const char *pszDevice, unsigned iInstance, unsigned iLun, PPDMIBASE *ppBase)
+{
+    LogFlow(("PDMR3UsbQueryLun: pszDevice=%p:{%s} iInstance=%u iLun=%u ppBase=%p\n",
+             pszDevice, pszDevice, iInstance, iLun, ppBase));
+    UVM_ASSERT_VALID_EXT_RETURN(pUVM, VERR_INVALID_VM_HANDLE);
+    PVM pVM = pUVM->pVM;
+    VM_ASSERT_VALID_EXT_RETURN(pVM, VERR_INVALID_VM_HANDLE);
+
+    /*
+     * Find the LUN.
+     */
+    PPDMLUN pLun;
+    int rc = pdmR3UsbFindLun(pVM, pszDevice, iInstance, iLun, &pLun);
+    if (RT_SUCCESS(rc))
+    {
+        if (pLun->pTop)
+        {
+            *ppBase = &pLun->pTop->IBase;
+            LogFlow(("PDMR3UsbQueryLun: return %Rrc and *ppBase=%p\n", VINF_SUCCESS, *ppBase));
+            return VINF_SUCCESS;
+        }
+        rc = VERR_PDM_NO_DRIVER_ATTACHED_TO_LUN;
+    }
+    LogFlow(("PDMR3UsbQueryLun: returns %Rrc\n", rc));
     return rc;
 }
Index: /trunk/src/VBox/VMM/VMMR3/VMMR3.def
===================================================================
--- /trunk/src/VBox/VMM/VMMR3/VMMR3.def	(revision 51289)
+++ /trunk/src/VBox/VMM/VMMR3/VMMR3.def	(revision 51290)
@@ -4,5 +4,5 @@
 
 ;
-; Copyright (C) 2010-2013 Oracle Corporation
+; Copyright (C) 2010-2014 Oracle Corporation
 ;
 ; This file is part of VirtualBox Open Source Edition (OSE), as
@@ -193,4 +193,5 @@
     PDMR3UsbDriverAttach
     PDMR3UsbDriverDetach
+    PDMR3UsbQueryLun
 
     PGMHandlerPhysicalPageTempOff