## @file # PCD DXE driver manage database contains all dynamic PCD entries and produce the implementation of PCD protocol. # # This version PCD DXE depends on the external PCD database binary file, not built in PCD data base. # There are two PCD Protocols as follows: # 1) PCD_PROTOCOL # It is EDKII implementation which support Dynamic/DynamicEx type Pcds. # 2) EFI_PCD_PROTOCOL # 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_PROTOCOL and EFI_PCD_PROTOCOL. # PCD DXE driver will produce above two protocols at same time. # # PCD database is generated as the separate binary image at build time. The binary image # will be intergrated into Firmware volume together with PCD driver. # # //////////////////////////////////////////////////////////////////////////////// # // // # // Introduction of PCD database // # // // # //////////////////////////////////////////////////////////////////////////////// # # 1, Introduction # PCD database hold all dynamic type PCD information. 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 used for the configuration/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 one of below cases: # a) The PCD setting value is produced by someone driver and consumed by # other driver in execution time. # b) The PCD setting value is set/get by user from FrontPage. # c) The PCD setting value is produced by platform OEM vendor in specified area. # # 2.2 According to module distribution way, dynamic PCD could be classfied as: # a) Dynamic: # If module is released in source code and will be built with platform # DSC, the dynamic PCD used by this module can be accessed as: # PcdGetxx(PcdSampleDynamicPcd); # In building platform, build tools will translate PcdSampleDynamicPcd to # pair of {Token Space Guid: Token Number} for this PCD. # b) DynamicEx: # If module is release as binary and will not pariticpate platform building, # the dynamic PCD used by this module need be accessed as: # PcdGetxxEx(gEfiMyTokenspaceGuid, PcdSampleDynamicPcd) # Developer need explicity gives {Token Space Guid:Token Number} as parameter # in writting source code. # # 2.3 According to PCD value's storage method, dynamic PCD could be classfied as: # a) Default Storage: # - The PCD value is stored in PCD database maintained by PCD driver in boot # time memory. # - 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] is used as section name for this type PCD in # platform DSC file. [PcdsDynamicExDefault] is used for dynamicEx type PCD. # # b) Variable Storage: # - The PCD value is stored in variable area. # - As default storage type, this type PCD could be used for PEI/DXE driver # communication. But beside it, this type PCD could also be used to store # the value associate with a HII setting via variable interface. # - In PEI phase, the PCD value could only be got but can not be set due # to variable area is readonly. # - [PcdsDynamicHii] is used as section name for this type PCD in platform # DSC file. [PcdsDynamicExHii] is for dynamicEx type PCD. # # c) OEM specificed storage area: # - The PCD value is stored in OEM specified area which base address is # specified by PCD setting - PcdVpdBaseAddress64 or PcdVpdBaseAddress. # - The area is read only for PEI and DXE phase. # - [PcdsDynamicVpd] is used as section name for this type PCD in platform # DSC file. [PcdsDynamicExVpd] is for dynamicex type PCD. # # 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 the 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 the separate binary file 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 the binary data base from flash # 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_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 binary file # PCD Database binary file will be created at build time as the standalone binary image. # To understand the binary image layout, PCD Database C structure is still generated # as comments 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 GUID. # - 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 # # Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.
# # SPDX-License-Identifier: BSD-2-Clause-Patent # # ## [Defines] INF_VERSION = 0x00010005 BASE_NAME = PcdDxe MODULE_UNI_FILE = PcdDxe.uni FILE_GUID = 80CF7257-87AB-47f9-A3FE-D50B76D89541 MODULE_TYPE = DXE_DRIVER VERSION_STRING = 4.0 PCD_IS_DRIVER = DXE_PCD_DRIVER ENTRY_POINT = PcdDxeInit # # The following information is for reference only and not required by the build tools. # # VALID_ARCHITECTURES = IA32 X64 EBC # [Sources] Pcd.c Service.c Service.h [Packages] MdePkg/MdePkg.dec MdeModulePkg/MdeModulePkg.dec [LibraryClasses] UefiRuntimeServicesTableLib BaseMemoryLib UefiBootServicesTableLib MemoryAllocationLib HobLib UefiDriverEntryPoint UefiLib DebugLib BaseLib PcdLib DxeServicesLib [Guids] gPcdDataBaseHobGuid ## SOMETIMES_CONSUMES ## HOB gPcdDataBaseSignatureGuid ## CONSUMES ## GUID # PCD database signature GUID. gEfiMdeModulePkgTokenSpaceGuid ## SOMETIMES_CONSUMES ## GUID [Protocols] gPcdProtocolGuid ## PRODUCES gEfiPcdProtocolGuid ## PRODUCES gGetPcdInfoProtocolGuid ## SOMETIMES_PRODUCES gEfiGetPcdInfoProtocolGuid ## SOMETIMES_PRODUCES ## NOTIFY ## SOMETIMES_CONSUMES gEdkiiVariableLockProtocolGuid [Pcd] gEfiMdeModulePkgTokenSpaceGuid.PcdVpdBaseAddress ## SOMETIMES_CONSUMES gEfiMdeModulePkgTokenSpaceGuid.PcdVpdBaseAddress64 ## SOMETIMES_CONSUMES gEfiMdeModulePkgTokenSpaceGuid.PcdSetNvStoreDefaultId ## SOMETIMES_CONSUMES [Depex] TRUE [UserExtensions.TianoCore."ExtraFiles"] PcdDxeExtra.uni