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292 lines
14 KiB
Plaintext
292 lines
14 KiB
Plaintext
// /** @file
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// PCD DXE driver manage database contains all dynamic PCD entries and produce the implementation of PCD protocol.
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//
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// This version PCD DXE depends on the external PCD database binary file, not built in PCD data base.
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// There are two PCD Protocols as follows:
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// 1) PCD_PROTOCOL
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// It is EDKII implementation which support Dynamic/DynamicEx type Pcds.
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// 2) EFI_PCD_PROTOCOL
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// It is defined by PI specification 1.2, Vol 3 which only support dynamicEx
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// type Pcd.
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//
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// For dynamicEx type PCD, it is compatible between PCD_PROTOCOL and EFI_PCD_PROTOCOL.
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// PCD DXE driver will produce above two protocols at same time.
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//
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// PCD database is generated as the separate binary image at build time. The binary image
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// will be intergrated into Firmware volume together with PCD driver.
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//
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// ////////////////////////////////////////////////////////////////////////////////
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// // //
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// // Introduction of PCD database //
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// // //
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// ////////////////////////////////////////////////////////////////////////////////
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//
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// 1, Introduction
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// PCD database hold all dynamic type PCD information. The structure of PEI PCD
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// database is generated by build tools according to dynamic PCD usage for
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// specified platform.
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//
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// 2, Dynamic Type PCD
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// Dynamic type PCD is used for the configuration/setting which value is determined
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// dynamic. In contrast, the value of static type PCD (FeatureFlag, FixedPcd,
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// PatchablePcd) is fixed in final generated FD image in build time.
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//
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// 2.1 The "dynamic" determination means one of below cases:
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// a) The PCD setting value is produced by someone driver and consumed by
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// other driver in execution time.
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// b) The PCD setting value is set/get by user from FrontPage.
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// c) The PCD setting value is produced by platform OEM vendor in specified area.
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//
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// 2.2 According to module distribution way, dynamic PCD could be classfied as:
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// a) Dynamic:
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// If module is released in source code and will be built with platform
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// DSC, the dynamic PCD used by this module can be accessed as:
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// PcdGetxx(PcdSampleDynamicPcd);
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// In building platform, build tools will translate PcdSampleDynamicPcd to
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// pair of {Token Space Guid: Token Number} for this PCD.
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// b) DynamicEx:
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// If module is release as binary and will not pariticpate platform building,
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// the dynamic PCD used by this module need be accessed as:
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// PcdGetxxEx(gEfiMyTokenspaceGuid, PcdSampleDynamicPcd)
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// Developer need explicity gives {Token Space Guid:Token Number} as parameter
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// in writting source code.
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//
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// 2.3 According to PCD value's storage method, dynamic PCD could be classfied as:
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// a) Default Storage:
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// - The PCD value is stored in PCD database maintained by PCD driver in boot
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// time memory.
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// - This type is used for communication between PEIM/DXE driver, DXE/DXE
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// driver. But all set/get value will be losted after boot-time memory
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// is turn off.
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// - [PcdsDynamicDefault] is used as section name for this type PCD in
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// platform DSC file. [PcdsDynamicExDefault] is used for dynamicEx type PCD.
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//
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// b) Variable Storage:
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// - The PCD value is stored in variable area.
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// - As default storage type, this type PCD could be used for PEI/DXE driver
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// communication. But beside it, this type PCD could also be used to store
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// the value associate with a HII setting via variable interface.
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// - In PEI phase, the PCD value could only be got but can not be set due
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// to variable area is readonly.
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// - [PcdsDynamicHii] is used as section name for this type PCD in platform
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// DSC file. [PcdsDynamicExHii] is for dynamicEx type PCD.
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//
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// c) OEM specificed storage area:
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// - The PCD value is stored in OEM specified area which base address is
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// specified by a FixedAtBuild PCD setting - PcdVpdBaseAddress.
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// - The area is read only for PEI and DXE phase.
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// - [PcdsDynamicVpd] is used as section name for this type PCD in platform
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// DSC file. [PcdsDynamicExVpd] is for dynamicex type PCD.
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//
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// 2.4 When and how to use dynamic PCD
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// Module developer do not care the used PCD is dynamic or static when writting
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// source code/INF. Dynamic PCD and dynamic type is pointed by platform integrator
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// in platform DSC file. Please ref section 2.3 to get matching between dynamic
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// PCD type and section name in DSC file.
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//
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// 3, PCD database:
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// Although dynamic PCD could be in different storage type as above description,
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// but the basic information and default value for all dynamic PCD is hold
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// by PCD database maintained by PEI/DXE driver.
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//
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// As the whole EFI BIOS boot path is divided into PEI/DXE phase, the PCD database
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// also is divided into Pei/Dxe database maintaied by PcdPeim/PcdDxe driver separatly.
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// To make PcdPeim's driver image smaller, PEI PCD database only hold all dynamic
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// PCD information used in PEI phase or use in both PEI/DXE phase. And DXE PCD
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// database contains all PCDs used in PEI/DXE phase in memory.
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//
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// Build tool will generate PCD database into the separate binary file for
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// PEI/DXE PCD driver according to dynamic PCD section in platform DSC file.
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//
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// 3.1 PcdPeim and PcdDxe
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// PEI PCD database is maintained by PcdPeim driver run from flash. PcdPeim driver
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// build guid hob in temporary memory and copy the binary data base from flash
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// to temporary memory for PEI PCD database.
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// DXE PCD database is maintained by PcdDxe driver.At entry point of PcdDxe driver,
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// a new PCD database is allocated in boot-time memory which including all
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// PEI PCD and DXE PCD entry.
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//
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// Pcd driver should run as early as possible before any other driver access
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// dynamic PCD's value. PEI/DXE "Apriori File" mechanism make it possible by
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// making PcdPeim/PcdDxe as first dispatching driver in PEI/DXE phase.
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//
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// 3.2 Token space Guid/Token number, Platform token, Local token number
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// Dynamic PCD
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// +-----------+ +---------+
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// |TokenSpace | |Platform |
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// | Guid | build tool | Token |
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// | + +-------------->| Number |
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// | Token | +---------+`._
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// | Number | `.
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// +-----------+ `. +------+
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// `-|Local |
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// |Token |
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// DynamicEx PCD ,-|Number|
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// +-----------+ ,-' +------+
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// |TokenSpace | ,-'
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// | Guid | _,-'
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// | + +.'
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// | Token |
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// | Number |
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// +-----------+
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//
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//
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// 3.2.1 Pair of Token space guid + Token number
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// Any type PCD is identified by pair of "TokenSpaceGuid + TokeNumber". But it
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// is not easy maintained by PCD driver, and hashed token number will make
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// searching slowly.
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//
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// 3.2.2 Platform Token Number
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// "Platform token number" concept is introduced for mapping to a pair of
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// "TokenSpaceGuid + TokenNumber". The platform token number is generated by
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// build tool in autogen.h and all of them are continual in a platform scope
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// started from 1.(0 meaning invalid internal token number)
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// With auto-generated "platform token number", PcdGet(PcdSampleDynamicPcd)
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// in source code is translated to LibPcdGet(_PCD_TOKEN_PcdSampleDynamicPcd)
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// in autogen.h.
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// Notes: The mapping between pair of "tokenspace guid + token number" and
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// "internal token number" need build tool establish, so "platform token number"
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// mechanism is not suitable for binary module which use DynamicEx type PCD.
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// To access a dynamicEx type PCD, pair of "token space guid/token number" all need
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// to be specificed for PcdSet/PcdGet accessing macro.
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//
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// Platform Token Number is started from 1, and inceased continuous. From whole
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// platform scope, there are two zones: PEI Zone and DXE Zone
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// | Platform Token Number
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// ----------|----------------------------------------------------------------
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// PEI Zone: | 1 ~ PEI_LOCAL_TOKEN_NUMBER
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// DXE Zone: | (PEI_LOCAL_TOKEN_NUMBER + 1) ~ (PEI_LOCAL_TOKEN_NUMBER + DXE_LOCAL_TOKEN_NUMBER)
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//
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// 3.2.3 Local Token Number
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// To fast searching a PCD entry in PCD database, PCD driver translate
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// platform token number to local token number via a mapping table.
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// For binary DynamicEx type PCD, there is a another mapping table to translate
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// "token space guid + token number" to local token number directly.
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// Local token number is identifier for all internal interface in PCD PEI/DXE
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// driver.
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//
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// A local token number is a 32-bit value in following meaning:
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// 32 ------------- 28 ---------- 24 -------- 0
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// | PCD type mask | Datum Type | Offset |
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// +-----------------------------------------+
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// where:
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// PCd type mask: indicate Pcd type from following macro:
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// PCD_TYPE_DATA
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// PCD_TYPE_HII
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// PCD_TYPE_VPD
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// PCD_TYPE_STRING
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// Datum Type : indicate PCD vaue type from following macro:
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// PCD_DATUM_TYPE_POINTER
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// PCD_DATUM_TYPE_UINT8
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// PCD_DATUM_TYPE_UINT16
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// PCD_DATUM_TYPE_UINT32
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// PCD_DATUM_TYPE_UINT64
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// Offset : indicate the related offset of PCD value in PCD database array.
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// Based on local token number, PCD driver could fast determine PCD type, value
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// type and get PCD entry from PCD database.
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//
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// 3.3 PCD Database binary file
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// PCD Database binary file will be created at build time as the standalone binary image.
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// To understand the binary image layout, PCD Database C structure is still generated
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// as comments by build tools in PCD driver's autogen.h/
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// autogen.c file. In generated C structure, following information is stored:
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// - ExMapTable: This table is used translate a binary dynamicex type PCD's
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// "tokenguid + token" to local token number.
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// - LocalTokenNumberTable:
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// This table stores all local token number in array, use "Internal
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// token number" as array index to get PCD entry's offset fastly.
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// - SizeTable: This table stores the size information for all PCD entry.
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// - GuidTable: This table stores guid value for DynamicEx's token space,
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// HII type PCD's variable GUID.
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// - SkuIdTable: TBD
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// - SystemSkuId: TBD
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// - PCD value structure:
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// Every PCD has a value record in PCD database. For different
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// datum type PCD has different record structure which will be
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// introduced in 3.3.1
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//
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// In a PCD database structure, there are two major area: Init and UnInit.
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// Init area is use stored above PCD internal structure such as ExMapTable,
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// LocalTokenNumberTable etc and the (default) value of PCD which has default
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// value specified in platform DSC file.
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// Unint area is used stored the value of PCD which has no default value in
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// platform DSC file, the value of NULL, 0 specified in platform DSC file can
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// be seemed as "no default value".
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//
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// 3.3.1 Simple Sample PCD Database C Structure
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// A general sample of PCD database structue is as follows:
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// typedef struct _PCD_DATABASE {
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// typedef struct _PCD_DATABASE_INIT {
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// //===== Following is PCD database internal maintain structures
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// DYNAMICEX_MAPPING ExMapTable[PEI_EXMAPPING_TABLE_SIZE];
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// UINT32 LocalTokenNumberTable[PEI_LOCAL_TOKEN_NUMBER_TABLE_SIZE];
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// GUID GuidTable[PEI_GUID_TABLE_SIZE];
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// SIZE_INFO SizeTable[PEI_SIZE_TABLE_SIZE];
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// UINT8 SkuIdTable[PEI_SKUID_TABLE_SIZE];
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// SKU_ID SystemSkuId;
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//
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// //===== Following is value structure for PCD with default value
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// ....
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// ....
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// ....
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// } Init;
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// typedef struct _PCD_DATABSE_UNINIT {
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// //==== Following is value structure for PCD without default value
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// ....
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// ....
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// } UnInit;
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// }
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//
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// 3.3.2 PCD value structure in PCD database C structure
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// The value's structure is generated by build tool in PCD database C structure.
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// The PCDs in different datum type has different value structure.
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//
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// 3.3.2.1 UINT8/UINT16/UINT32/UINT64 datum type PCD
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// The C structure for these datum type PCD is just a UINT8/UINT16/UINT32/UINT64
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// data member in PCD database, For example:
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// UINT16 PcdHardwareErrorRecordLevel_d3705011_bc19_4af7_be16_f68030378c15_VariableDefault_0;
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// Above structure is generated by build tool, the member name is "PcdCName_Guidvalue"
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// Member type is UINT16 according to PcdHardwareErrorRecordLevel declaration
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// in DEC file.
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//
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// 3.3.2.2 VOID* datum type PCD
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// The value of VOID* datum type PCD is a UINT8/UINT16 array in PCD database.
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//
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// 3.3.2.2.1 VOID* - string type
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// If the default value for VOID* datum type PCD like L"xxx", the PCD is
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// used for unicode string, and C structure of this datum type PCD is
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// UINT16 string array in PCD database, for example:
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// UINT16 StringTable[29];
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// The number of 29 in above sample is max size of a unicode string.
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//
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// If the default value for VOID* datum type PCD like "xxx", the PCD is
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// used for ascii string, and C structure of this datum type PCD is
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// UINT8 string array in PCD database, for example:
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// UINT8 StringTable[20];
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// The number of 20 in above sample is max size of a ascii string.
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//
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// 3.3.2.2.2 VOID* - byte array
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// If the default value of VOID* datum type PCD like {'0x29', '0x01', '0xf2'}
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// the PCD is used for byte array. The generated structrue is same as
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// above ascii string table,
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// UINT8 StringTable[13];
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// The number of 13 in above sample is max size of byte array.
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//
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// 3.3.3 Some utility structures in PCD Database
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// 3.3.3.1 GuidTable
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// GuidTable array is used to store all related GUID value in PCD database:
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// - Variable GUID for HII type PCD
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// - Token space GUID for dynamicex type PCD
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//
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// Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
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//
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// SPDX-License-Identifier: BSD-2-Clause-Patent
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//
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// **/
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#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"
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#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."
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