[edk2-devel] The principles of EDK2 module reconstruction for archs

[Ni, Ray]

The [Arch] refers to the Processor Architecture.
The [Module] refer to the EDK2 module.
The [X86] refers to both IA32 and X64.
The principles to create the X86 folder in the module:

  1.  When X86-vendor's implementation is introduced to the existing module:

  1.  The folder reconstruction:
A-1. If the module is obviously used by IA32/X64 only

  *   No need to create X86 folder
  *   Create X86-vendor's stuff under the root directory of module
A-2. If the existing module is expected to accommodate the different archs or the module already has multiple archs:

  *   Create X86 folder
  *   Create X86-vendor's stuff under X86 folder
[Ray] Looks good.


  1.  The files reconstruction:
B-1. The module INF metafile

  *   The existing INF metafile should be kept without relocation. Should not have the impacts to the existing DSC/FDF file.
  *   The new introduced INF metafile should be located under the root directory of module with the file naming format as below. This keeps the consistent module file structure.
     *   <OriginalFileName><arch>.inf
[Ray]  "CpuDxe.inf" and "CpuDxeArm.inf"? is that your intention? New developers may be confused that CpuDxe.inf supports only X86 arch.
Do you have an example that one module supporting multiple archs using different INF files? MdeModulePkg/DxeIpl is a module supporting different archs with the same INF file.
Or shall we leave it to be decided between the patch contributor and package/module maintainer?


                     B-2. Source files
                              The new arch implementation is introduced to the module in order to leverage the source code and the module design architecture, so

  *   That is contributor's responsibility to review the source code and strip the arch-dependent code away and put it into the arch-specific file. Leave the common code in the original file if there is no arch-specific and arch-specific-feature wordings in the file name. Create a common file for the common implementation otherwise.
     *   The file naming for the arch-specific file

<OriginalFileName ><arch>.*

     *   The file naming for the common implementation

< OriginalFileNaming >Common.*

  *   That is contributor's responsibility to relocate the arch-specific source files to the arch-specific folder.
  *   That is contributor's responsibility to make sure the original INF metafile can properly pull-in the source file from arch-specific folder after the source file reconstruction.
  *   The common source files should be located under the root directory of module
[Ray] If you check the MpInitLib, most of SEV logic are moved to AmdSev.c. But MpLib.c still contains logic to call functions from AmdSev.c based on some AMD specific check. In my opinion, that's already good enough.
However, if you check MdeModulePkg/DxeIpl, implementations for different archs are in different *folders*.
Can we leave this to the module owner to decide how to place the implementations?



  1.  When a new arch's implementation is introduced to the existing module which was developed for the specific arch:

  1.  The folder reconstruction:

  *   Create arch folder for the existing arch implementation
[Ray] Do you move existing arch implementation to that arch folder? It will break existing platforms a lot.

  *   Create the arch folder for the new introduced arch
[Ray] I agree. But if we don't create arch folder for existing arch implementation, the pkg layout will be a mess.

[Ray] Hard for me to understand all the principles here. Maybe we review existing code including to-be-upstreamed code and decide how to go.


  1.  The files reconstruction:

B-1. The module INF metafile

  *   The existing INF file should be kept without the relocation. Should not have the impacts to the existing DSC/FDF file.
  *   The new introduced INF metafile should be located under the root directory of module with the file naming format as below. This keeps the consistent module file structure.
     *   < OriginalFileNaming><arch>.inf



B-2. Source files
                             The new arch implementation is introduced to this module in order to leverage the source code and the module design architecture, so

  *   That is contributor's responsibility to review the source code and strip the arch-dependent code away and put it into the arch-specific file. Leave the common code in the original file if there is no arch-specific wording in the file name. Create a common file for the common implementation otherwise.
     *   The file naming for the arch-specific source file

< OriginalFileNaming ><arch>.*

     *   The file naming for the common implementation

<OriginalFileNaming>Common.*

  *   That is contributor's responsibility to relocate the arch-specific source files to the arch-specific folder.
  *   That is contributor's responsibility to make sure the original INF metafile can properly pull-in the source file from arch-specific folder after the source file reconstruction.
  *   The common source files should be located under the root directory of module



  1.  When a new arch implementation has a huge delta with the original implementation

Create a separate module instance. The naming of the module should follow below format,

  *   Add the arch prefix with the original module name:

< OriginalModuleNaming><arch>




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