1// /** @file 2// PCD DXE driver manage database contains all dynamic PCD entries and produce the implementation of PCD protocol. 3// 4// This version PCD DXE depends on the external PCD database binary file, not built in PCD data base. 5// There are two PCD Protocols as follows: 6// 1) PCD_PROTOCOL 7// It is EDKII implementation which support Dynamic/DynamicEx type Pcds. 8// 2) EFI_PCD_PROTOCOL 9// It is defined by PI specification 1.2, Vol 3 which only support dynamicEx 10// type Pcd. 11// 12// For dynamicEx type PCD, it is compatible between PCD_PROTOCOL and EFI_PCD_PROTOCOL. 13// PCD DXE driver will produce above two protocols at same time. 14// 15// PCD database is generated as the separate binary image at build time. The binary image 16// will be intergrated into Firmware volume together with PCD driver. 17// 18// //////////////////////////////////////////////////////////////////////////////// 19// // // 20// // Introduction of PCD database // 21// // // 22// //////////////////////////////////////////////////////////////////////////////// 23// 24// 1, Introduction 25// PCD database hold all dynamic type PCD information. The structure of PEI PCD 26// database is generated by build tools according to dynamic PCD usage for 27// specified platform. 28// 29// 2, Dynamic Type PCD 30// Dynamic type PCD is used for the configuration/setting which value is determined 31// dynamic. In contrast, the value of static type PCD (FeatureFlag, FixedPcd, 32// PatchablePcd) is fixed in final generated FD image in build time. 33// 34// 2.1 The "dynamic" determination means one of below cases: 35// a) The PCD setting value is produced by someone driver and consumed by 36// other driver in execution time. 37// b) The PCD setting value is set/get by user from FrontPage. 38// c) The PCD setting value is produced by platform OEM vendor in specified area. 39// 40// 2.2 According to module distribution way, dynamic PCD could be classfied as: 41// a) Dynamic: 42// If module is released in source code and will be built with platform 43// DSC, the dynamic PCD used by this module can be accessed as: 44// PcdGetxx(PcdSampleDynamicPcd); 45// In building platform, build tools will translate PcdSampleDynamicPcd to 46// pair of {Token Space Guid: Token Number} for this PCD. 47// b) DynamicEx: 48// If module is release as binary and will not pariticpate platform building, 49// the dynamic PCD used by this module need be accessed as: 50// PcdGetxxEx(gEfiMyTokenspaceGuid, PcdSampleDynamicPcd) 51// Developer need explicity gives {Token Space Guid:Token Number} as parameter 52// in writting source code. 53// 54// 2.3 According to PCD value's storage method, dynamic PCD could be classfied as: 55// a) Default Storage: 56// - The PCD value is stored in PCD database maintained by PCD driver in boot 57// time memory. 58// - This type is used for communication between PEIM/DXE driver, DXE/DXE 59// driver. But all set/get value will be losted after boot-time memory 60// is turn off. 61// - [PcdsDynamicDefault] is used as section name for this type PCD in 62// platform DSC file. [PcdsDynamicExDefault] is used for dynamicEx type PCD. 63// 64// b) Variable Storage: 65// - The PCD value is stored in variable area. 66// - As default storage type, this type PCD could be used for PEI/DXE driver 67// communication. But beside it, this type PCD could also be used to store 68// the value associate with a HII setting via variable interface. 69// - In PEI phase, the PCD value could only be got but can not be set due 70// to variable area is readonly. 71// - [PcdsDynamicHii] is used as section name for this type PCD in platform 72// DSC file. [PcdsDynamicExHii] is for dynamicEx type PCD. 73// 74// c) OEM specificed storage area: 75// - The PCD value is stored in OEM specified area which base address is 76// specified by a FixedAtBuild PCD setting - PcdVpdBaseAddress. 77// - The area is read only for PEI and DXE phase. 78// - [PcdsDynamicVpd] is used as section name for this type PCD in platform 79// DSC file. [PcdsDynamicExVpd] is for dynamicex type PCD. 80// 81// 2.4 When and how to use dynamic PCD 82// Module developer do not care the used PCD is dynamic or static when writting 83// source code/INF. Dynamic PCD and dynamic type is pointed by platform integrator 84// in platform DSC file. Please ref section 2.3 to get matching between dynamic 85// PCD type and section name in DSC file. 86// 87// 3, PCD database: 88// Although dynamic PCD could be in different storage type as above description, 89// but the basic information and default value for all dynamic PCD is hold 90// by PCD database maintained by PEI/DXE driver. 91// 92// As the whole EFI BIOS boot path is divided into PEI/DXE phase, the PCD database 93// also is divided into Pei/Dxe database maintaied by PcdPeim/PcdDxe driver separatly. 94// To make PcdPeim's driver image smaller, PEI PCD database only hold all dynamic 95// PCD information used in PEI phase or use in both PEI/DXE phase. And DXE PCD 96// database contains all PCDs used in PEI/DXE phase in memory. 97// 98// Build tool will generate PCD database into the separate binary file for 99// PEI/DXE PCD driver according to dynamic PCD section in platform DSC file. 100// 101// 3.1 PcdPeim and PcdDxe 102// PEI PCD database is maintained by PcdPeim driver run from flash. PcdPeim driver 103// build guid hob in temporary memory and copy the binary data base from flash 104// to temporary memory for PEI PCD database. 105// DXE PCD database is maintained by PcdDxe driver.At entry point of PcdDxe driver, 106// a new PCD database is allocated in boot-time memory which including all 107// PEI PCD and DXE PCD entry. 108// 109// Pcd driver should run as early as possible before any other driver access 110// dynamic PCD's value. PEI/DXE "Apriori File" mechanism make it possible by 111// making PcdPeim/PcdDxe as first dispatching driver in PEI/DXE phase. 112// 113// 3.2 Token space Guid/Token number, Platform token, Local token number 114// Dynamic PCD 115// +-----------+ +---------+ 116// |TokenSpace | |Platform | 117// | Guid | build tool | Token | 118// | + +-------------->| Number | 119// | Token | +---------+`._ 120// | Number | `. 121// +-----------+ `. +------+ 122// `-|Local | 123// |Token | 124// DynamicEx PCD ,-|Number| 125// +-----------+ ,-' +------+ 126// |TokenSpace | ,-' 127// | Guid | _,-' 128// | + +.' 129// | Token | 130// | Number | 131// +-----------+ 132// 133// 134// 3.2.1 Pair of Token space guid + Token number 135// Any type PCD is identified by pair of "TokenSpaceGuid + TokeNumber". But it 136// is not easy maintained by PCD driver, and hashed token number will make 137// searching slowly. 138// 139// 3.2.2 Platform Token Number 140// "Platform token number" concept is introduced for mapping to a pair of 141// "TokenSpaceGuid + TokenNumber". The platform token number is generated by 142// build tool in autogen.h and all of them are continual in a platform scope 143// started from 1.(0 meaning invalid internal token number) 144// With auto-generated "platform token number", PcdGet(PcdSampleDynamicPcd) 145// in source code is translated to LibPcdGet(_PCD_TOKEN_PcdSampleDynamicPcd) 146// in autogen.h. 147// Notes: The mapping between pair of "tokenspace guid + token number" and 148// "internal token number" need build tool establish, so "platform token number" 149// mechanism is not suitable for binary module which use DynamicEx type PCD. 150// To access a dynamicEx type PCD, pair of "token space guid/token number" all need 151// to be specificed for PcdSet/PcdGet accessing macro. 152// 153// Platform Token Number is started from 1, and inceased continuous. From whole 154// platform scope, there are two zones: PEI Zone and DXE Zone 155// | Platform Token Number 156// ----------|---------------------------------------------------------------- 157// PEI Zone: | 1 ~ PEI_LOCAL_TOKEN_NUMBER 158// DXE Zone: | (PEI_LOCAL_TOKEN_NUMBER + 1) ~ (PEI_LOCAL_TOKEN_NUMBER + DXE_LOCAL_TOKEN_NUMBER) 159// 160// 3.2.3 Local Token Number 161// To fast searching a PCD entry in PCD database, PCD driver translate 162// platform token number to local token number via a mapping table. 163// For binary DynamicEx type PCD, there is a another mapping table to translate 164// "token space guid + token number" to local token number directly. 165// Local token number is identifier for all internal interface in PCD PEI/DXE 166// driver. 167// 168// A local token number is a 32-bit value in following meaning: 169// 32 ------------- 28 ---------- 24 -------- 0 170// | PCD type mask | Datum Type | Offset | 171// +-----------------------------------------+ 172// where: 173// PCd type mask: indicate Pcd type from following macro: 174// PCD_TYPE_DATA 175// PCD_TYPE_HII 176// PCD_TYPE_VPD 177// PCD_TYPE_SKU_ENABLED 178// PCD_TYPE_STRING 179// Datum Type : indicate PCD vaue type from following macro: 180// PCD_DATUM_TYPE_POINTER 181// PCD_DATUM_TYPE_UINT8 182// PCD_DATUM_TYPE_UINT16 183// PCD_DATUM_TYPE_UINT32 184// PCD_DATUM_TYPE_UINT64 185// Offset : indicate the related offset of PCD value in PCD database array. 186// Based on local token number, PCD driver could fast determine PCD type, value 187// type and get PCD entry from PCD database. 188// 189// 3.3 PCD Database binary file 190// PCD Database binary file will be created at build time as the standalone binary image. 191// To understand the binary image layout, PCD Database C structure is still generated 192// as comments by build tools in PCD driver's autogen.h/ 193// autogen.c file. In generated C structure, following information is stored: 194// - ExMapTable: This table is used translate a binary dynamicex type PCD's 195// "tokenguid + token" to local token number. 196// - LocalTokenNumberTable: 197// This table stores all local token number in array, use "Internal 198// token number" as array index to get PCD entry's offset fastly. 199// - SizeTable: This table stores the size information for all PCD entry. 200// - GuidTable: This table stores guid value for DynamicEx's token space, 201// HII type PCD's variable GUID. 202// - SkuIdTable: TBD 203// - SystemSkuId: TBD 204// - PCD value structure: 205// Every PCD has a value record in PCD database. For different 206// datum type PCD has different record structure which will be 207// introduced in 3.3.1 208// 209// In a PCD database structure, there are two major area: Init and UnInit. 210// Init area is use stored above PCD internal structure such as ExMapTable, 211// LocalTokenNumberTable etc and the (default) value of PCD which has default 212// value specified in platform DSC file. 213// Unint area is used stored the value of PCD which has no default value in 214// platform DSC file, the value of NULL, 0 specified in platform DSC file can 215// be seemed as "no default value". 216// 217// 3.3.1 Simple Sample PCD Database C Structure 218// A general sample of PCD database structue is as follows: 219// typedef struct _PCD_DATABASE { 220// typedef struct _PCD_DATABASE_INIT { 221// //===== Following is PCD database internal maintain structures 222// DYNAMICEX_MAPPING ExMapTable[PEI_EXMAPPING_TABLE_SIZE]; 223// UINT32 LocalTokenNumberTable[PEI_LOCAL_TOKEN_NUMBER_TABLE_SIZE]; 224// GUID GuidTable[PEI_GUID_TABLE_SIZE]; 225// SIZE_INFO SizeTable[PEI_SIZE_TABLE_SIZE]; 226// UINT8 SkuIdTable[PEI_SKUID_TABLE_SIZE]; 227// SKU_ID SystemSkuId; 228// 229// //===== Following is value structure for PCD with default value 230// .... 231// .... 232// .... 233// } Init; 234// typedef struct _PCD_DATABSE_UNINIT { 235// //==== Following is value structure for PCD without default value 236// .... 237// .... 238// } UnInit; 239// } 240// 241// 3.3.2 PCD value structure in PCD database C structure 242// The value's structure is generated by build tool in PCD database C structure. 243// The PCDs in different datum type has different value structure. 244// 245// 3.3.2.1 UINT8/UINT16/UINT32/UINT64 datum type PCD 246// The C structure for these datum type PCD is just a UINT8/UINT16/UINT32/UINT64 247// data member in PCD database, For example: 248// UINT16 PcdHardwareErrorRecordLevel_d3705011_bc19_4af7_be16_f68030378c15_VariableDefault_0; 249// Above structure is generated by build tool, the member name is "PcdCName_Guidvalue" 250// Member type is UINT16 according to PcdHardwareErrorRecordLevel declaration 251// in DEC file. 252// 253// 3.3.2.2 VOID* datum type PCD 254// The value of VOID* datum type PCD is a UINT8/UINT16 array in PCD database. 255// 256// 3.3.2.2.1 VOID* - string type 257// If the default value for VOID* datum type PCD like L"xxx", the PCD is 258// used for unicode string, and C structure of this datum type PCD is 259// UINT16 string array in PCD database, for example: 260// UINT16 StringTable[29]; 261// The number of 29 in above sample is max size of a unicode string. 262// 263// If the default value for VOID* datum type PCD like "xxx", the PCD is 264// used for ascii string, and C structure of this datum type PCD is 265// UINT8 string array in PCD database, for example: 266// UINT8 StringTable[20]; 267// The number of 20 in above sample is max size of a ascii string. 268// 269// 3.3.2.2.2 VOID* - byte array 270// If the default value of VOID* datum type PCD like {'0x29', '0x01', '0xf2'} 271// the PCD is used for byte array. The generated structrue is same as 272// above ascii string table, 273// UINT8 StringTable[13]; 274// The number of 13 in above sample is max size of byte array. 275// 276// 3.3.3 Some utility structures in PCD Database 277// 3.3.3.1 GuidTable 278// GuidTable array is used to store all related GUID value in PCD database: 279// - Variable GUID for HII type PCD 280// - Token space GUID for dynamicex type PCD 281// 282// Copyright (c) 2006 - 2014, Intel Corporation. All rights reserved.<BR> 283// 284// This program and the accompanying materials 285// are licensed and made available under the terms and conditions of the BSD License 286// which accompanies this distribution. The full text of the license may be found at 287// http://opensource.org/licenses/bsd-license.php 288// THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, 289// WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. 290// 291// **/ 292 293 294#string STR_MODULE_ABSTRACT #language en-US "PCD DXE driver manages the database that contains all dynamic PCD entries and produce the implementation of PCD protocol" 295 296#string STR_MODULE_DESCRIPTION #language en-US "PCD DXE driver manages the database that contains all dynamic PCD entries and produces the implementation of PCD protocol." 297 298