Add introduction of PCD database in PCD PEIM.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@7973 6f19259b-4bc3-4df7-8a09-765794883524

1 files changed, 249 insertions, 1 deletions

diff --git a/MdeModulePkg/Universal/PCD/Pei/Service.h b/MdeModulePkg/Universal/PCD/Pei/Service.h
index be0d502..9ac393f 100644
--- a/MdeModulePkg/Universal/PCD/Pei/Service.h
+++ b/MdeModulePkg/Universal/PCD/Pei/Service.h
@@ -893,7 +893,7 @@ typedef struct {
   space guid: token number} to local token number.

   

   @param Guid            Token space guid for dynamic-ex PCD entry.

-  @param ExTokenNumber   EDES_TODO: Add parameter description

+  @param ExTokenNumber   Token number for dynamic-ex PCD.

 

   @return local token number for dynamic-ex PCD.

 

@@ -1011,3 +1011,251 @@ SetPtrTypeSize (
 extern PEI_PCD_DATABASE_INIT gPEIPcdDbInit;

 

 #endif

+

+////////////////////////////////////////////////////////////////////////////////

+//                                                                            //

+//                      Introduction of PEI 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.

+      

+      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.

+          

+**/