1, PeiPcdLib use EFI_PEI_PCD_PPI defined in PI 1.2 to handle dynamicEx type PCD request.

2, DxePcdLib use EFI_PCD_PROTOCOL defined in PI 1.2 to handle dynamicEx type PCD request.
3, There is no change for dynamic type PCD.
4, Refine the INF's comments.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@9473 6f19259b-4bc3-4df7-8a09-765794883524

MdePkg/Library/PeiPcdLib/PeiPcdLib.inf

@@ -1,9 +1,21 @@
 #/** @file
 # Instance of PCD Library using PCD PPI.
 #
+# There are two PCD PPIs as follows:
+#   1) PCD_PPI 
+#      It is EDKII implementation which support Dynamic/DynamicEx Pcds.
+#   2) EFI_PEI_PCD_PPI
+#      It is defined by PI specification 1.2, Vol 3 which only support dynamicEx 
+#      type Pcd.
+# For dynamicEx type PCD, it is compatible between PCD_PPI and EFI_PEI_PCD_PPI.
+# This library instance uses the PCD_PPI to handle dynamic PCD request and use
+# EFI_PEI_PCD_PPI to handle dynamicEx type PCD.
+#
+# This library instance assume the PCD_PPI and EFI_PEI_PCD_PPI are both installed early.
+#
 # PCD Library that uses the PCD PPI to access Dynamic and DynamicEx PCD entries
 #
-# Copyright (c) 2007 - 2008, Intel Corporation
+# Copyright (c) 2007 - 2009, Intel Corporation
 #
 #  All rights reserved. This program and the accompanying materials
 #  are licensed and made available under the terms and conditions of the BSD License
@@ -44,6 +56,8 @@
 
 [Ppis]
   gPcdPpiGuid                                   ## CONSUMES
-
+  gEfiPeiPcdPpiGuid                             ## CONSUMES
+  
 [depex]
-  gPcdPpiGuid
+  gEfiPeiPcdPpiGuid
+