// /** @file // PCD PEIM produces PCD database to manage all dynamic PCD in PEI phase and install Pcd Ppi service. // // This version PCD PEIM depends on the external PCD database binary file, not built in PCD data base. // There are two PCD PPIs as follows: // 1) PCD_PPI // It is EDKII implementation which support Dynamic/DynamicEx Pcds. // 2) EFI_PEI_PCD_PPI // 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_PPI and EFI_PEI_PCD_PPI. // PCD PEIM driver will produce above two PPIs 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 a FixedAtBuild PCD setting - 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 // // **/ #string STR_MODULE_ABSTRACT #language en-US "PCD PEIM produces PCD database to manage all dynamic PCD in PEI phase and install Pcd Ppi service." #string STR_MODULE_DESCRIPTION #language en-US "PCD PEIM produces PCD database to manage all dynamic PCD in PEI phase and install Pcd Ppi service."