4.3 File Names

4.3.1 There is no limit to file name lengths.

Do not assume that file names must be 8.3 compatible. Be reasonable though. Let the file names be as long as necessary, but no longer. Some operating systems limit file names to 32 characters.

4.3.2 Spaces in file and directory names are NOT permitted.

Allowing spaces would cause problems with certain versions of existing industry tools and does not provide additional clarity.

4.3.3 Never start file names with numbers.

Most source control systems will not be able to handle file names that start with numbers.

4.3.4 Non-standard characters shall not occur in file names.

All file names within an EDK II source tree must comply with the following regular expression:

[A-Za-z][_A-Za-z0-9-]*[A-Za-z0-9]+

That is, a letter followed by zero, or more, letters, underscores, dashes, or digits followed by a period followed by one or more letters or digits.

4.3.5 File naming guidelines for modules

Below sections are the file naming guidelines for EDK II meta files and source files. The guidelines are not just considering the the uniformity of file naming, but it also provides the flexibility of file name construction for the scenario of different EDK II module designs; such as the support for multiple processor architectures and vendors. It may require the further discussions between EDK II maintainers and contributors in order to determine the best naming of the EDK II module file.

4.3.5.1 EDK II meta files within a package

<PackageName>Pkg.dec
<PackageName>Pkg.dsc

   <PackageName> REQUIRED  *

4.3.5.2 EDK II INF file within a Module instance

• If the implementation is for all CPU architectures, specific CPU architectures, CPU vendors or the implementation is shared by certain CPU archs:

<Feature><Phase>[<CpuArch>][<Vendor>].inf

   <Feature>      REQUIRED    *
   <Phase>        REQUIRED    Base, Sec, Pei, Dxe, DxeRuntime, Mm, StandaloneMm,
                              Smm, Uefi.
   <CpuArch>      OPTIONAL    The <CpuArch> is represented with a BNF,
                              <arch> ::='Ia32' | 'X64' | 'Arm' | 'AArch64' | 'RiscV64' |
                                        'LoongArch64' | 'Ebc'
                              <CpuArch> ::= <arch>[<arch>]*

                              Example: Ia32X64Arm or RiscV64LoongArch64
   <Vendor>       OPTIONAL    *

Example:
   - SmbiosDxe.inf
   - CpuIo2Dxe.inf
   - CpuIo2DxeAmd.inf
   - CpuIo2DxeIa32X64.inf
   - CpuIo2DxeIa32X64Intel.inf

• If the implementation does not have any shared code between phases (e.g., Pcd/Dxe):

[<Feature>][<CpuArch>][<Vendor>].inf

   <Feature>      OPTIONAL    *
   <CpuArch>      OPTIONAL    The <CpuArch> is represented with a BNF,
                              <arch> ::='Ia32' | 'X64' | 'Arm' | 'AArch64' | 'RiscV64' |
                                        'LoongArch64' | 'Ebc'
                              <CpuArch> ::= <arch>[<arch>]*

                              Example: Ia32X64Arm or RiscV64LoongArch64
   <Vendor>       OPTIONAL    *
Example:
   Pcd.inf

4.3.5.3 EDK II INF file within a Library instance

<Phase>[<CpuArch>][<Vendor>]<LibraryClassName>[<Dependency>].inf
   <Phase>              REQUIRED     Base, Sec, Pei, Dxe, DxeRuntime, Mm,
                                     StandaloneMm, Smm, Uefi.
   <CpuArch>            OPTIONAL     The <CpuArch> is represented with a BNF,
                                     <arch> ::='Ia32' | 'X64' | 'Arm' | 'AArch64' | 'RiscV64' |
                                               'LoongArch64' | 'Ebc'
                                     <CpuArch> ::= <arch>[<arch>]*

                                     Example: Ia32X64Arm or RiscV64LoongArch64
   <Vendor>             OPTIONAL     *
   <LibraryClassName>   REQUIRED     *
   <Dependency>         OPTIONAL     * (Typically name of PPI, Protocol, LibraryClass
                                       that the implementation is layered on top of)

Example:
   - SmmAmdSmmCpuFeaturesLib.inf
   - SmmIa32X64SmmCpuFeaturesLib.inf

4.3.5.4 EDK II source files within a Library/Module instance

In generally, the file name is constructed as below:

[<CpuArch>][<Vendor>]<FileName>.*

   <CpuArch>   OPTIONAL   The <CpuArch> is represented with a BNF,
                          <arch> ::='Ia32' | 'X64' | 'Arm' | 'AArch64' | 'RiscV64' |
                                    'LoongArch64' | 'Ebc'
                          <CpuArch> ::= <arch>[<arch>]*

                          Example: Ia32X64Arm or RiscV64LoongArch64
   <Vendor>    OPTIONAL   *
   <FileName>  REQUIRED   Refer to 4.3.1 to 4.3.4 sections for the file
                          naming format.

Example:
   SmmCpuFeatureLib.c
   SmmCpuFeatureLibCommon.c
   Ia32X64SmmCpuFeaturesLib.c
   Ia32X64IntelSmmCpuFeaturesLib.c
   AmdSmmCpuFeaturesLib.c