1 files changed, 53 insertions, 14 deletions

diff --git a/sys/contrib/dev/acpica/excreate.c b/sys/contrib/dev/acpica/excreate.c
index ce2f25e74b86..332f3b55dd60 100644
--- a/sys/contrib/dev/acpica/excreate.c
+++ b/sys/contrib/dev/acpica/excreate.c
@@ -1,7 +1,7 @@
 /******************************************************************************
  *
  * Module Name: excreate - Named object creation
- *              $Revision: 93 $
+ *              $Revision: 94 $
  *
  *****************************************************************************/
 
@@ -146,7 +146,8 @@ ACPI_STATUS
 AcpiExCreateAlias (
     ACPI_WALK_STATE         *WalkState)
 {
-    ACPI_NAMESPACE_NODE     *SourceNode;
+    ACPI_NAMESPACE_NODE     *TargetNode;
+    ACPI_NAMESPACE_NODE     *AliasNode;
     ACPI_STATUS             Status;
 
 
@@ -155,25 +156,63 @@ AcpiExCreateAlias (
 
     /* Get the source/alias operands (both namespace nodes) */
 
-    SourceNode = (ACPI_NAMESPACE_NODE *) WalkState->Operands[1];
+    AliasNode =  (ACPI_NAMESPACE_NODE *) WalkState->Operands[0];
+    TargetNode = (ACPI_NAMESPACE_NODE *) WalkState->Operands[1];
 
-
-    /* Attach the original source object to the new Alias Node */
-
-    Status = AcpiNsAttachObject ((ACPI_NAMESPACE_NODE *) WalkState->Operands[0],
-                                    AcpiNsGetAttachedObject (SourceNode),
-                                    SourceNode->Type);
+    if (TargetNode->Type == INTERNAL_TYPE_ALIAS)
+    {
+        /* 
+         * Dereference an existing alias so that we don't create a chain
+         * of aliases.  With this code, we guarantee that an alias is
+         * always exactly one level of indirection away from the 
+         * actual aliased name.
+         */
+        TargetNode = (ACPI_NAMESPACE_NODE *) TargetNode->Object;
+    }
 
     /*
-     * The new alias assumes the type of the source, but it points
-     * to the same object.  The reference count of the object has an
-     * additional reference to prevent deletion out from under either the
-     * source or the alias Node
+     * For objects that can never change (i.e., the NS node will
+     * permanently point to the same object), we can simply attach
+     * the object to the new NS node.  For other objects (such as
+     * Integers, buffers, etc.), we have to point the Alias node
+     * to the original Node.
      */
+    switch (TargetNode->Type)
+    {
+    case ACPI_TYPE_INTEGER:
+    case ACPI_TYPE_STRING:
+    case ACPI_TYPE_BUFFER:
+    case ACPI_TYPE_PACKAGE:
+    case ACPI_TYPE_BUFFER_FIELD:
+
+        /*
+         * The new alias has the type ALIAS and points to the original
+         * NS node, not the object itself.  This is because for these
+         * types, the object can change dynamically via a Store.
+         */
+        AliasNode->Type = INTERNAL_TYPE_ALIAS;
+        AliasNode->Object = (ACPI_OPERAND_OBJECT *) TargetNode;
+        break;
+
+    default:
+
+        /* Attach the original source object to the new Alias Node */
+
+        /*
+         * The new alias assumes the type of the target, and it points
+         * to the same object.  The reference count of the object has an
+         * additional reference to prevent deletion out from under either the
+         * target node or the alias Node
+         */
+        Status = AcpiNsAttachObject (AliasNode,
+                                AcpiNsGetAttachedObject (TargetNode),
+                                TargetNode->Type);
+        break;
+    }
 
     /* Since both operands are Nodes, we don't need to delete them */
 
-    return_ACPI_STATUS (Status);
+    return_ACPI_STATUS (AE_OK);
 }