From dc8d93ca0c9a798fe4e23f68b5b5adc032bf5509 Mon Sep 17 00:00:00 2001
From: eric_tian <eric_tian@6f19259b-4bc3-4df7-8a09-765794883524>
Date: Tue, 23 Sep 2008 14:49:45 +0000
Subject: [PATCH] add detail comments on the complicated code segment.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@5954 6f19259b-4bc3-4df7-8a09-765794883524
---
 MdeModulePkg/Core/Dxe/Mem/Page.c | 23 ++++++++++++++---------
 MdeModulePkg/Core/Dxe/Mem/Pool.c |  4 ++++
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/MdeModulePkg/Core/Dxe/Mem/Page.c b/MdeModulePkg/Core/Dxe/Mem/Page.c
index 5e3c81d786..c55bbe3b92 100644
--- a/MdeModulePkg/Core/Dxe/Mem/Page.c
+++ b/MdeModulePkg/Core/Dxe/Mem/Page.c
@@ -35,18 +35,20 @@ typedef struct {
 //
 UINTN     mMemoryMapKey = 0;
 
-//
-// mMapStack - space to use as temp storage to build new map descriptors
-// mMapDepth - depth of new descriptor stack
-//
-
 #define MAX_MAP_DEPTH 6
+
+///
+/// mMapDepth - depth of new descriptor stack
+///
 UINTN         mMapDepth = 0;
+///
+/// mMapStack - space to use as temp storage to build new map descriptors
+///
 MEMORY_MAP    mMapStack[MAX_MAP_DEPTH];
 UINTN         mFreeMapStack = 0;
-//
-// This list maintain the free memory map list
-//
+///
+/// This list maintain the free memory map list
+///
 LIST_ENTRY   mFreeMemoryMapEntryList = INITIALIZE_LIST_HEAD_VARIABLE (mFreeMemoryMapEntryList);
 BOOLEAN      mMemoryTypeInformationInitialized = FALSE;
 
@@ -1287,7 +1289,10 @@ CoreGetMemoryMap (
     if ((GcdMapEntry->GcdMemoryType == EfiGcdMemoryTypeReserved) ||
         (GcdMapEntry->GcdMemoryType == EfiGcdMemoryTypeMemoryMappedIo)) {
       if ((GcdMapEntry->Attributes & EFI_MEMORY_RUNTIME) == EFI_MEMORY_RUNTIME) {
-
+        // 
+        // Create EFI_MEMORY_DESCRIPTOR for every Reserved and MMIO GCD entries
+        // that are marked for runtime use
+        //
         MemoryMap->PhysicalStart = GcdMapEntry->BaseAddress;
         MemoryMap->VirtualStart  = 0;
         MemoryMap->NumberOfPages = RShiftU64 ((GcdMapEntry->EndAddress - GcdMapEntry->BaseAddress + 1), EFI_PAGE_SHIFT);
diff --git a/MdeModulePkg/Core/Dxe/Mem/Pool.c b/MdeModulePkg/Core/Dxe/Mem/Pool.c
index cea6fada4c..ce70cff513 100644
--- a/MdeModulePkg/Core/Dxe/Mem/Pool.c
+++ b/MdeModulePkg/Core/Dxe/Mem/Pool.c
@@ -124,6 +124,10 @@ LookupPoolHead (
     return &mPoolHead[MemoryType];
   }
 
+  //
+  // MemoryType values in the range 0x80000000..0xFFFFFFFF are reserved for use by UEFI 
+  // OS loaders that are provided by operating system vendors
+  //
   if (MemoryType < 0) {
 
     for (Link = mPoolHeadList.ForwardLink; Link != &mPoolHeadList; Link = Link->ForwardLink) {
-- 
2.39.2