Add clarification for PcdAcpiDefault value PCD.

[mirror_edk2.git] / MdeModulePkg / MdeModulePkg.dec

diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
index 5ec37c5a7d056d5809d5e8c4e1e22f07ca217909..e2e0b75cdb31aaf8ce2bf63d74a908b1956ecf79 100644 (file)
--- a/MdeModulePkg/MdeModulePkg.dec
+++ b/MdeModulePkg/MdeModulePkg.dec
@@ -1408,18 +1408,32 @@
   gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiDefaultOemId|"INTEL "|VOID*|0x30001034\r
 \r
   ## Default OEM Table ID for ACPI table creation, it is "EDK2    ".\r
+  #  Accroding to ACPI specification, this field is particularly useful when\r
+  #  defining a definition block to distinguish definition block functions.\r
+  #  The OEM assigns each dissimilar table a new OEM Table ID.\r
+  #  This PCD is ignored for definition block.\r
   # @Prompt Default OEM Table ID for ACPI table creation.\r
   gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiDefaultOemTableId|0x20202020324B4445|UINT64|0x30001035\r
 \r
   ## Default OEM Revision for ACPI table creation.\r
+  #  Accroding to ACPI specification, for LoadTable() opcode, the OS can also\r
+  #  check the OEM Table ID and Revision ID against a database for a newer\r
+  #  revision Definition Block of the same OEM Table ID and load it instead.\r
+  #  This PCD is ignored for definition block.\r
   # @Prompt Default OEM Revision for ACPI table creation.\r
   gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiDefaultOemRevision|0x00000002|UINT32|0x30001036\r
 \r
   ## Default Creator ID for ACPI table creation.\r
+  #  Accroding to ACPI specification, for tables containing Definition Blocks,\r
+  #  this is the ID for the ASL Compiler.\r
+  #  This PCD is ignored for definition block.\r
   # @Prompt Default Creator ID for ACPI table creation.\r
   gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiDefaultCreatorId|0x20202020|UINT32|0x30001037\r
 \r
   ## Default Creator Revision for ACPI table creation.\r
+  #  Accroding to ACPI specification, for tables containing Definition Blocks,\r
+  #  this is the revision for the ASL Compiler.\r
+  #  This PCD is ignored for definition block.\r
   # @Prompt Default Creator Revision for ACPI table creation.\r
   gEfiMdeModulePkgTokenSpaceGuid.PcdAcpiDefaultCreatorRevision|0x01000013|UINT32|0x30001038\r
 \r