1, Move introduction from header file to INF file header; 2, Refine dynamic PCD introduction according to review comments

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@7997 6f19259b-4bc3-4df7-8a09-765794883524

1 files changed, 0 insertions, 260 deletions

diff --git a/MdeModulePkg/Universal/PCD/Pei/Service.h b/MdeModulePkg/Universal/PCD/Pei/Service.h
index 3a25f57e24..ce786a9072 100644
--- a/MdeModulePkg/Universal/PCD/Pei/Service.h
+++ b/MdeModulePkg/Universal/PCD/Pei/Service.h
@@ -1012,263 +1012,3 @@ extern PEI_PCD_DATABASE_INIT gPEIPcdDbInit;
 

 #endif

 

-////////////////////////////////////////////////////////////////////////////////

-//                                                                            //

-//                      Introduction of PCD database                          //

-//                                                                            //

-////////////////////////////////////////////////////////////////////////////////

-/**

- 1, Introduction

-    PEI PCD database hold all dynamic type PCD information used in PEI phase.

-    The structure of PEI PCD database is generated by build tools according to

-    dynamic PCD usage for specified platform.

-    

- 2, Dynamic Type PCD

-    Dynamic type PCD is designed for accessing setting which value is determined

-    dynamic. In contrast, the value of static type PCD (FeatureFlag, FixedPcd, 

-    PatchablePcd) is fixed in final generated FD image in build time. 

-        

-    2.1 The "dynamic" determination means:

-      a) The PCD value is produced by someone driver and consumed by other driver

-         in execution time.

-      b) The PCD value is set/get by user from FrontPage.

-      c) The PCD value is produced by platform OEM specified area.

-    

-    2.2 According to distribution mehod, dynamic PCD could be classfied as:

-      a) Dynamic:

-         This type PCD is used for module in source distribution which will be 

-         built in platform.

-      b) DynamicEx:

-         This type PCD is used for module in binary distribution which will be 

-         will not built.

-         

-    2.3 According to storage method, dynamic PCD could be classfied as:

-      a) Default Storage: 

-         - The value is stored in PCD database maintained by PCD database in boot 

-           time memory which is built as a guid hob in PEI phase.

-         - This type is used for communication between PEIM/DXE driver, DXE/DXE 

-           driver. But all set/get value will be losted after boot-time memory 

-           is turn off.

-         - [PcdsDynamicDefault]/[PcdsDynamicExDefault] is used as section name 

-           for this type PCD in platform DSC file.

-         

-      b) Variable Storage: 

-         - The value is stored in variable area. 

-         - As default storage type, this type PCD could used for communication.

-           But beside it, this type PCD could be used store the value associating 

-           with HII setting via variable technology.

-         - In PEI phase, the PCD value could only be got but can not be set due 

-           to variable area is readonly for PEI phase.

-         - [PcdsDynamicHii]/[PcdsDynamicExHii] is used as section name for this 

-           type PCD in platform DSC file.

-           

-      c) OEM specificed storage area:

-         - The value is stored in OEM specified area, the base address is specified

-           by a FixedAtBuild PCD PcdVpdBaseAddress.

-         - The area is read only for PEI and DXE phase.

-         - [PcdsDynamicVpd]/[PcdsDynamicExVpd] is used as section name for this 

-           type PCD in platform DSC file.

-      

-      Note: The default value of dynamic PCD are storaged in memory maintained

-            by PEI/DXE PCD drvier.

-            

-    2.4 When and how to use dynamic PCD

-      Module developer do not care the used PCD is dynamic or static when writting

-      source code/INF. Dynamic PCD and dynamic type is pointed by platform integrator 

-      in platform DSC file. Please ref section 2.3 to get matching between dynamic

-      PCD type and section name in DSC file.

-    

- 3, PCD database:

-    Although dynamic PCD could be in different storage type as above description, 

-    but the basic information and default value for all dynamic PCD is hold

-    by PCD database maintained by PEI/DXE driver.

-    

-    As whole EFI BIOS boot path is divided into PEI/DXE phase, the PCD database

-    also is divided into Pei/Dxe database maintaied by PcdPeim/PcdDxe driver separatly.

-    To make PcdPeim's driver image smaller, PEI PCD database only hold all dynamic

-    PCD information used in PEI phase or use in both PEI/DXE phase. And DXE PCD

-    database contains all PCDs used in PEI/DXE phase in memory.

-    

-    Build tool will generate PCD database into some C structure and variable for 

-    PEI/DXE PCD driver according to dynamic PCD section in platform DSC file. 

-    

-    3.1 PcdPeim and PcdDxe

-      PEI PCD database is maintained by PcdPeim driver run from flash. PcdPeim driver

-      build guid hob in temporary memory and copy auto-generated C structure 

-      to temporary memory for PEI PCD database. 

-      DXE PCD database is maintained by PcdDxe driver.At entry point of PcdDxe driver,

-      a new PCD database is allocated in boot-time memory which including all

-      PEI PCD and DXE PCD entry.

-      

-      Pcd driver should run as early as possible before any other driver access

-      dynamic PCD's value. PEI/DXE "Apriori File" mechanism make it possible by

-      making PcdPeim/PcdDxe as first dispatching driver in PEI/DXE phase.

-      

-    3.2 Token space Guid/Token number, Platform token, Local token number

-           Dynamic PCD

-          +-----------+               +---------+

-          |TokenSpace |               |Platform |

-          |   Guid    |  build tool   | Token   |

-          |    +      +-------------->| Number  |

-          |  Token    |               +---------+`._

-          |  Number   |                             `.

-          +-----------+                               `.  +------+

-                                                        `-|Local |

-                                                          |Token |

-                               DynamicEx PCD            ,-|Number|

-                               +-----------+         ,-'  +------+

-                               |TokenSpace |      ,-'

-                               |   Guid    |  _,-'

-                               |    +      +.'

-                               |  Token    |

-                               |  Number   |

-                               +-----------+

-    

-    

-      3.2.1 Pair of Token space guid + Token number

-        Any type PCD is identified by pair of "TokenSpaceGuid + TokeNumber". But it

-        is not easy maintained by PCD driver, and hashed token number will make 

-        searching slowly. 

-

-      3.2.2 Platform Token Number

-        "Platform token number" concept is introduced for mapping to a pair of 

-        "TokenSpaceGuid + TokenNumber". The platform token number is generated by 

-        build tool in autogen.h and all of them are continual in a platform scope 

-        started from 1.(0 meaning invalid internal token number)

-        With auto-generated "platform token number", PcdGet(PcdSampleDynamicPcd)

-        in source code is translated to LibPcdGet(_PCD_TOKEN_PcdSampleDynamicPcd) 

-        in autogen.h.

-        Notes: The mapping between pair of "tokenspace guid + token number" and

-        "internal token number" need build tool establish, so "platform token number"

-        mechanism is not suitable for binary module which use DynamicEx type PCD.

-        To access a dynamicEx type PCD, pair of "token space guid/token number" all need

-        to be specificed for PcdSet/PcdGet accessing macro.

-      

-        Platform Token Number is started from 1, and inceased continuous. From whole 

-        platform scope, there are two zones: PEI Zone and DXE Zone

-                  |                      Platform Token Number

-        ----------|----------------------------------------------------------------

-        PEI Zone: |            1                 ~  PEI_LOCAL_TOKEN_NUMBER

-        DXE Zone: | (PEI_LOCAL_TOKEN_NUMBER + 1) ~ (PEI_LOCAL_TOKEN_NUMBER + DXE_LOCAL_TOKEN_NUMBER)

-        

-      3.2.3 Local Token Number

-        To fast searching a PCD entry in PCD database, PCD driver translate 

-        platform token number to local token number via a mapping table.

-        For binary DynamicEx type PCD, there is a another mapping table to translate

-        "token space guid + token number" to local token number directly.

-        Local token number is identifier for all internal interface in PCD PEI/DXE

-        driver.

-        

-        A local token number is a 32-bit value in following meaning:

-         32 ------------- 28 ---------- 24 -------- 0

-          | PCD type mask  | Datum Type  |  Offset  |

-          +-----------------------------------------+

-        where:

-          PCd type mask: indicate Pcd type from following macro:

-                         PCD_TYPE_DATA

-                         PCD_TYPE_HII

-                         PCD_TYPE_VPD

-                         PCD_TYPE_SKU_ENABLED

-                         PCD_TYPE_STRING

-          Datum Type   : indicate PCD vaue type from following macro:

-                         PCD_DATUM_TYPE_POINTER

-                         PCD_DATUM_TYPE_UINT8

-                         PCD_DATUM_TYPE_UINT16

-                         PCD_DATUM_TYPE_UINT32

-                         PCD_DATUM_TYPE_UINT64

-          Offset      : indicate the related offset of PCD value in PCD database array.

-       Based on local token number, PCD driver could fast determine PCD type, value

-       type and get PCD entry from PCD database.

-       

-    3.3 PCD Database C structure.

-      PCD Database C structure is generated by build tools in PCD driver's autogen.h/

-      autogen.c file. In generated C structure, following information is stored:

-      - ExMapTable: This table is used translate a binary dynamicex type PCD's 

-                    "tokenguid + token" to local token number.

-      - LocalTokenNumberTable:

-                    This table stores all local token number in array, use "Internal

-                    token number" as array index to get PCD entry's offset fastly.

-      - SizeTable:  This table stores the size information for all PCD entry.

-      - GuidTable:  This table stores guid value for DynamicEx's token space,

-                    HII type PCD's variable.

-      - SkuIdTable: TBD

-      - SystemSkuId: TBD

-      - PCD value structure:  

-                    Every PCD has a value record in PCD database. For different

-                    datum type PCD has different record structure which will be 

-                    introduced in 3.3.1

-      

-      In a PCD database structure, there are two major area: Init and UnInit. 

-      Init area is use stored above PCD internal structure such as ExMapTable, 

-      LocalTokenNumberTable etc and the (default) value of PCD which has default 

-      value specified in platform DSC file.

-      Unint area is used stored the value of PCD which has no default value in

-      platform DSC file, the value of NULL, 0 specified in platform DSC file can

-      be seemed as "no default value".

-      

-      3.3.1 Simple Sample PCD Database C Structure

-        A general sample of PCD database structue is as follows:

-        typedef struct _PCD_DATABASE {

-          typedef struct _PCD_DATABASE_INIT {

-            //===== Following is PCD database internal maintain structures

-            DYNAMICEX_MAPPING ExMapTable[PEI_EXMAPPING_TABLE_SIZE];

-            UINT32            LocalTokenNumberTable[PEI_LOCAL_TOKEN_NUMBER_TABLE_SIZE];

-            GUID              GuidTable[PEI_GUID_TABLE_SIZE];

-            SIZE_INFO         SizeTable[PEI_SIZE_TABLE_SIZE];

-            UINT8             SkuIdTable[PEI_SKUID_TABLE_SIZE];

-            SKU_ID            SystemSkuId;

-            

-            //===== Following is value structure for PCD with default value

-            ....

-            ....

-            ....

-          } Init;

-          typedef struct _PCD_DATABSE_UNINIT {

-            //==== Following is value structure for PCD without default value

-            ....

-            ....

-          } UnInit;

-        }

-      

-      3.3.2 PCD value structure in PCD database C structure

-        The value's structure is generated by build tool in PCD database C structure.

-        The PCDs in different datum type has different value structure.

-        

-        3.3.2.1 UINT8/UINT16/UINT32/UINT64 datum type PCD

-          The C structure for these datum type PCD is just a UINT8/UINT16/UINT32/UINT64

-          data member in PCD database, For example:

-          UINT16  PcdHardwareErrorRecordLevel_d3705011_bc19_4af7_be16_f68030378c15_VariableDefault_0;

-          Above structure is generated by build tool, the member name is "PcdCName_Guidvalue"

-          Member type is UINT16 according to PcdHardwareErrorRecordLevel declaration

-          in DEC file.

-          

-        3.3.2.2 VOID* datum type PCD

-          The value of VOID* datum type PCD is a UINT8/UINT16 array in PCD database.

-          

-          3.3.2.2.1 VOID* - string type

-            If the default value for VOID* datum type PCD like L"xxx", the PCD is 

-            used for unicode string, and C structure of this datum type PCD is 

-            UINT16 string array in PCD database, for example:

-            UINT16 StringTable[29];

-            The number of 29 in above sample is max size of a unicode string.

-            

-            If the default value for VOID* datum type PCD like "xxx", the PCD is

-            used for ascii string, and C structure of this datum type PCD is 

-            UINT8 string array in PCD database, for example:

-            UINT8 StringTable[20];

-            The number of 20 in above sample is max size of a ascii string.

-            

-          3.3.2.2.2 VOID* - byte array

-            If the default value of VOID* datum type PCD like {'0x29', '0x01', '0xf2'}

-            the PCD is used for byte array. The generated structrue is same as 

-            above ascii string table,

-            UINT8 StringTable[13];

-            The number of 13 in above sample is max size of byte array.

-       

-      3.3.3 Some utility structures in PCD Database

-        3.3.3.1 GuidTable

-          GuidTable array is used to store all related GUID value in PCD database:

-            - Variable GUID for HII type PCD

-            - Token space GUID for dynamicex type PCD 

-    

-**/