--- xnu/xnu-792/iokit/Kernel/IOMultiMemoryDescriptor.cpp
+++ xnu/xnu-124.1/iokit/Kernel/IOMultiMemoryDescriptor.cpp
@@ -87,7 +87,7 @@
                                   IOMemoryDescriptor ** descriptors,
                                   UInt32                withCount,
                                   IODirection           withDirection,
-                                  bool                  asReference )
+                                  bool                  asReference = false )
 {
     //
     // Create a new IOMultiMemoryDescriptor.  The "buffer" is made up of several
@@ -118,7 +118,7 @@
                                   IOMemoryDescriptor ** descriptors,
                                   UInt32                withCount,
                                   IODirection           withDirection,
-                                  bool                  asReference )
+                                  bool                  asReference = false )
 {
     //
     // Initialize an IOMultiMemoryDescriptor. The "buffer" is made up of several
@@ -131,19 +131,10 @@
     assert(descriptors);
     assert(withCount);
 
-    // Release existing descriptors, if any
-    if ( _descriptors )
-    {
-        for ( unsigned index = 0; index < _descriptorsCount; index++ ) 
-            _descriptors[index]->release();
-
-        if ( _descriptorsIsAllocated )
-            IODelete(_descriptors, IOMemoryDescriptor *, _descriptorsCount);
-    } else {
-        // Ask our superclass' opinion.
-        if ( super::init() == false )  return false;
-    }
-    
+    // Ask our superclass' opinion.
+
+    if ( super::init() == false )  return false;
+
     // Initialize our minimal state.
 
     _descriptors            = 0;
@@ -298,34 +289,6 @@
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
-IOPhysicalAddress IOMultiMemoryDescriptor::getSourceSegment(
-                                                       IOByteCount   offset,
-                                                       IOByteCount * length )
-{
-    //
-    // This method returns the physical address of the byte at the given offset
-    // into the memory,  and optionally the length of the physically contiguous
-    // segment from that offset.
-    //
-
-    assert(offset <= _length);
-
-    for ( unsigned index = 0; index < _descriptorsCount; index++ ) 
-    {
-        if ( offset < _descriptors[index]->getLength() )
-        {
-            return _descriptors[index]->getSourceSegment(offset, length);
-        }
-        offset -= _descriptors[index]->getLength();
-    }
-
-    if ( length )  *length = 0;
-
-    return 0;
-}
-
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-
 void * IOMultiMemoryDescriptor::getVirtualSegment( IOByteCount   /* offset */ ,
                                                    IOByteCount * /* length */ )
 {