space guid: token number} to local token number.\r
\r
@param Guid Token space guid for dynamic-ex PCD entry.\r
- @param ExTokenNumber EDES_TODO: Add parameter description\r
+ @param ExTokenNumber Token number for dynamic-ex PCD.\r
\r
@return local token number for dynamic-ex PCD.\r
\r
extern PEI_PCD_DATABASE_INIT gPEIPcdDbInit;\r
\r
#endif\r
+\r
+////////////////////////////////////////////////////////////////////////////////\r
+// //\r
+// Introduction of PEI PCD database //\r
+// //\r
+////////////////////////////////////////////////////////////////////////////////\r
+/**\r
+ 1, Introduction\r
+ PEI PCD database hold all dynamic type PCD information used in PEI phase.\r
+ The structure of PEI PCD database is generated by build tools according to\r
+ dynamic PCD usage for specified platform.\r
+ \r
+ 2, Dynamic Type PCD\r
+ Dynamic type PCD is designed for accessing setting which value is determined\r
+ dynamic. In contrast, the value of static type PCD (FeatureFlag, FixedPcd, \r
+ PatchablePcd) is fixed in final generated FD image in build time. \r
+ \r
+ 2.1 The "dynamic" determination means:\r
+ a) The PCD value is produced by someone driver and consumed by other driver\r
+ in execution time.\r
+ b) The PCD value is set/get by user from FrontPage.\r
+ c) The PCD value is produced by platform OEM specified area.\r
+ \r
+ 2.2 According to distribution mehod, dynamic PCD could be classfied as:\r
+ a) Dynamic:\r
+ This type PCD is used for module in source distribution which will be \r
+ built in platform.\r
+ b) DynamicEx:\r
+ This type PCD is used for module in binary distribution which will be \r
+ will not built.\r
+ \r
+ 2.3 According to storage method, dynamic PCD could be classfied as:\r
+ a) Default Storage: \r
+ - The value is stored in PCD database maintained by PCD database in boot \r
+ time memory which is built as a guid hob in PEI phase.\r
+ - This type is used for communication between PEIM/DXE driver, DXE/DXE \r
+ driver. But all set/get value will be losted after boot-time memory \r
+ is turn off.\r
+ - [PcdsDynamicDefault]/[PcdsDynamicExDefault] is used as section name \r
+ for this type PCD in platform DSC file.\r
+ \r
+ b) Variable Storage: \r
+ - The value is stored in variable area. \r
+ - As default storage type, this type PCD could used for communication.\r
+ But beside it, this type PCD could be used store the value associating \r
+ with HII setting via variable technology.\r
+ - In PEI phase, the PCD value could only be got but can not be set due \r
+ to variable area is readonly for PEI phase.\r
+ - [PcdsDynamicHii]/[PcdsDynamicExHii] is used as section name for this \r
+ type PCD in platform DSC file.\r
+ \r
+ c) OEM specificed storage area:\r
+ - The value is stored in OEM specified area, the base address is specified\r
+ by a FixedAtBuild PCD PcdVpdBaseAddress.\r
+ - The area is read only for PEI and DXE phase.\r
+ - [PcdsDynamicVpd]/[PcdsDynamicExVpd] is used as section name for this \r
+ type PCD in platform DSC file.\r
+ \r
+ Note: The default value of dynamic PCD are storaged in memory maintained\r
+ by PEI/DXE PCD drvier.\r
+ \r
+ 2.4 When and how to use dynamic PCD\r
+ Module developer do not care the used PCD is dynamic or static when writting\r
+ source code/INF. Dynamic PCD and dynamic type is pointed by platform integrator \r
+ in platform DSC file. Please ref section 2.3 to get matching between dynamic\r
+ PCD type and section name in DSC file.\r
+ \r
+ 3, PCD database:\r
+ Although dynamic PCD could be in different storage type as above description, \r
+ but the basic information and default value for all dynamic PCD is hold\r
+ by PCD database maintained by PEI/DXE driver.\r
+ \r
+ As whole EFI BIOS boot path is divided into PEI/DXE phase, the PCD database\r
+ also is divided into Pei/Dxe database maintaied by PcdPeim/PcdDxe driver separatly.\r
+ To make PcdPeim's driver image smaller, PEI PCD database only hold all dynamic\r
+ PCD information used in PEI phase or use in both PEI/DXE phase. And DXE PCD\r
+ database contains all PCDs used in PEI/DXE phase in memory.\r
+ \r
+ Build tool will generate PCD database into some C structure and variable for \r
+ PEI/DXE PCD driver according to dynamic PCD section in platform DSC file. \r
+ \r
+ 3.1 PcdPeim and PcdDxe\r
+ PEI PCD database is maintained by PcdPeim driver run from flash. PcdPeim driver\r
+ build guid hob in temporary memory and copy auto-generated C structure \r
+ to temporary memory for PEI PCD database. \r
+ DXE PCD database is maintained by PcdDxe driver.At entry point of PcdDxe driver,\r
+ a new PCD database is allocated in boot-time memory which including all\r
+ PEI PCD and DXE PCD entry.\r
+ \r
+ Pcd driver should run as early as possible before any other driver access\r
+ dynamic PCD's value. PEI/DXE "Apriori File" mechanism make it possible by\r
+ making PcdPeim/PcdDxe as first dispatching driver in PEI/DXE phase.\r
+ \r
+ 3.2 Token space Guid/Token number, Platform token, Local token number\r
+ Dynamic PCD\r
+ +-----------+ +---------+\r
+ |TokenSpace | |Platform |\r
+ | Guid | build tool | Token |\r
+ | + +-------------->| Number |\r
+ | Token | +---------+`._\r
+ | Number | `.\r
+ +-----------+ `. +------+\r
+ `-|Local |\r
+ |Token |\r
+ DynamicEx PCD ,-|Number|\r
+ +-----------+ ,-' +------+\r
+ |TokenSpace | ,-'\r
+ | Guid | _,-'\r
+ | + +.'\r
+ | Token |\r
+ | Number |\r
+ +-----------+\r
+ \r
+ \r
+ 3.2.1 Pair of Token space guid + Token number\r
+ Any type PCD is identified by pair of "TokenSpaceGuid + TokeNumber". But it\r
+ is not easy maintained by PCD driver, and hashed token number will make \r
+ searching slowly. \r
+\r
+ 3.2.2 Platform Token Number\r
+ "Platform token number" concept is introduced for mapping to a pair of \r
+ "TokenSpaceGuid + TokenNumber". The platform token number is generated by \r
+ build tool in autogen.h and all of them are continual in a platform scope \r
+ started from 1.(0 meaning invalid internal token number)\r
+ With auto-generated "platform token number", PcdGet(PcdSampleDynamicPcd)\r
+ in source code is translated to LibPcdGet(_PCD_TOKEN_PcdSampleDynamicPcd) \r
+ in autogen.h.\r
+ Notes: The mapping between pair of "tokenspace guid + token number" and\r
+ "internal token number" need build tool establish, so "platform token number"\r
+ mechanism is not suitable for binary module which use DynamicEx type PCD.\r
+ To access a dynamicEx type PCD, pair of "token space guid/token number" all need\r
+ to be specificed for PcdSet/PcdGet accessing macro.\r
+ \r
+ 3.2.3 Local Token Number\r
+ To fast searching a PCD entry in PCD database, PCD driver translate \r
+ platform token number to local token number via a mapping table.\r
+ For binary DynamicEx type PCD, there is a another mapping table to translate\r
+ "token space guid + token number" to local token number directly.\r
+ Local token number is identifier for all internal interface in PCD PEI/DXE\r
+ driver.\r
+ \r
+ A local token number is a 32-bit value in following meaning:\r
+ 32 ------------- 28 ---------- 24 -------- 0\r
+ | PCD type mask | Datum Type | Offset |\r
+ +-----------------------------------------+\r
+ where:\r
+ PCd type mask: indicate Pcd type from following macro:\r
+ PCD_TYPE_DATA\r
+ PCD_TYPE_HII\r
+ PCD_TYPE_VPD\r
+ PCD_TYPE_SKU_ENABLED\r
+ PCD_TYPE_STRING\r
+ Datum Type : indicate PCD vaue type from following macro:\r
+ PCD_DATUM_TYPE_POINTER\r
+ PCD_DATUM_TYPE_UINT8\r
+ PCD_DATUM_TYPE_UINT16\r
+ PCD_DATUM_TYPE_UINT32\r
+ PCD_DATUM_TYPE_UINT64\r
+ Offset : indicate the related offset of PCD value in PCD database array.\r
+ Based on local token number, PCD driver could fast determine PCD type, value\r
+ type and get PCD entry from PCD database.\r
+ \r
+ 3.3 PCD Database C structure.\r
+ PCD Database C structure is generated by build tools in PCD driver's autogen.h/\r
+ autogen.c file. In generated C structure, following information is stored:\r
+ - ExMapTable: This table is used translate a binary dynamicex type PCD's \r
+ "tokenguid + token" to local token number.\r
+ - LocalTokenNumberTable:\r
+ This table stores all local token number in array, use "Internal\r
+ token number" as array index to get PCD entry's offset fastly.\r
+ - SizeTable: This table stores the size information for all PCD entry.\r
+ - GuidTable: This table stores guid value for DynamicEx's token space,\r
+ HII type PCD's variable.\r
+ - SkuIdTable: TBD\r
+ - SystemSkuId: TBD\r
+ - PCD value structure: \r
+ Every PCD has a value record in PCD database. For different\r
+ datum type PCD has different record structure which will be \r
+ introduced in 3.3.1\r
+ \r
+ In a PCD database structure, there are two major area: Init and UnInit. \r
+ Init area is use stored above PCD internal structure such as ExMapTable, \r
+ LocalTokenNumberTable etc and the (default) value of PCD which has default \r
+ value specified in platform DSC file.\r
+ Unint area is used stored the value of PCD which has no default value in\r
+ platform DSC file, the value of NULL, 0 specified in platform DSC file can\r
+ be seemed as "no default value".\r
+ \r
+ 3.3.1 Simple Sample PCD Database C Structure\r
+ A general sample of PCD database structue is as follows:\r
+ typedef struct _PCD_DATABASE {\r
+ typedef struct _PCD_DATABASE_INIT {\r
+ //===== Following is PCD database internal maintain structures\r
+ DYNAMICEX_MAPPING ExMapTable[PEI_EXMAPPING_TABLE_SIZE];\r
+ UINT32 LocalTokenNumberTable[PEI_LOCAL_TOKEN_NUMBER_TABLE_SIZE];\r
+ GUID GuidTable[PEI_GUID_TABLE_SIZE];\r
+ SIZE_INFO SizeTable[PEI_SIZE_TABLE_SIZE];\r
+ UINT8 SkuIdTable[PEI_SKUID_TABLE_SIZE];\r
+ SKU_ID SystemSkuId;\r
+ \r
+ //===== Following is value structure for PCD with default value\r
+ ....\r
+ ....\r
+ ....\r
+ } Init;\r
+ typedef struct _PCD_DATABSE_UNINIT {\r
+ //==== Following is value structure for PCD without default value\r
+ ....\r
+ ....\r
+ } UnInit;\r
+ }\r
+ \r
+ 3.3.2 PCD value structure in PCD database C structure\r
+ The value's structure is generated by build tool in PCD database C structure.\r
+ The PCDs in different datum type has different value structure.\r
+ \r
+ 3.3.2.1 UINT8/UINT16/UINT32/UINT64 datum type PCD\r
+ The C structure for these datum type PCD is just a UINT8/UINT16/UINT32/UINT64\r
+ data member in PCD database, For example:\r
+ UINT16 PcdHardwareErrorRecordLevel_d3705011_bc19_4af7_be16_f68030378c15_VariableDefault_0;\r
+ Above structure is generated by build tool, the member name is "PcdCName_Guidvalue"\r
+ Member type is UINT16 according to PcdHardwareErrorRecordLevel declaration\r
+ in DEC file.\r
+ \r
+ 3.3.2.2 VOID* datum type PCD\r
+ The value of VOID* datum type PCD is a UINT8/UINT16 array in PCD database.\r
+ \r
+ 3.3.2.2.1 VOID* - string type\r
+ If the default value for VOID* datum type PCD like L"xxx", the PCD is \r
+ used for unicode string, and C structure of this datum type PCD is \r
+ UINT16 string array in PCD database, for example:\r
+ UINT16 StringTable[29];\r
+ The number of 29 in above sample is max size of a unicode string.\r
+ \r
+ If the default value for VOID* datum type PCD like "xxx", the PCD is\r
+ used for ascii string, and C structure of this datum type PCD is \r
+ UINT8 string array in PCD database, for example:\r
+ UINT8 StringTable[20];\r
+ The number of 20 in above sample is max size of a ascii string.\r
+ \r
+ 3.3.2.2.2 VOID* - byte array\r
+ If the default value of VOID* datum type PCD like {'0x29', '0x01', '0xf2'}\r
+ the PCD is used for byte array. The generated structrue is same as \r
+ above ascii string table,\r
+ UINT8 StringTable[13];\r
+ The number of 13 in above sample is max size of byte array.\r
+ \r
+**/\r
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