2 FDF Design Discussion

This section of the document provides an overview to processing Flash Description File (FDF) used to create firmware images, Option ROM images or bootable images for removable media. For the purposes of this design discussion, the FDF file will be referred to as FlashMap.fdf. By convention, the name "FlashMap.fdf" has been used for the flash description file. This is only a convention and developers can maintain different flash description files using different file names, for example a given size or model of flash part. The file can have any name, however it is recommended that developers use the FDF extension for all flash description files.

The flash description file is normally in the same directory as the platform description (DSC) file.

The remainder of this document uses "FDF" instead of "Flash Description File."

The EDK II Build generates UEFI and PI specification compliant binary images. The tools provided in the EDK and the EdkCompatibilityPkg module support earlier versions of the specifications.

This revision of the specification adds support for multiple binary files in an FV FILE RAW statement. FDF files that use this feature must use the new FDF_SPECIFICATION = 0x0001001C in the [Defines] section. Older FDF files do not need to update the FDF_SPECIFICATION value.

The EDK II build system has been updated to allow the setting of multiple paths that will be searched when attempting to resolve the location of EDK II packages. This new feature allows for more flexibility when designing a tree layout or combining sources from different sources. The new functionality is enabled through the addition of a new environment variable (PACKAGES_PATH).

The PACKAGES_PATH variable is an ordered list of additional search paths using the default path separator of the host OS between each entry ( ";" on Windows, ":" on Linux and OS/X). The path specified by the WORKSPACE variable always has the highest search priority over any PACKAGE_PATH entries. The first path (left to right) in the PACKAGES_PATH list has the highest priority and the last path has the lowest priority.

Build tools will stop searching when the first location is resolved.

For the remainder of this document, unless otherwise specified (using "system environment variable, WORKSPACE"), references to the WORKSPACE and $(WORKSPACE) refer to the ordered list of directories specified by the combination of WORKSPACE + PACKAGES_PATH. The build system will automatically join the directories and search these paths to locate content, with the first match terminating the search. For example given the following set of environment variables, and the MdeModulePkg is located in both the edk2 and edk2Copy directories, the build system would use the C:\work\edk2\MdeModulePkg when attempting to locate the MdeModulePkg.dec file.

set WORKSPACE=c:\work
set PACKAGES_PATH=c:\work\edk2;c:\work\edk2Copy

Build tools will stop searching when the first location is resolved.

Refer to the TianoCore.org web-site for more information on the EDK II build system.

Note: Path and Filename elements within the FDF are case-sensitive in order to support building on UNIX style operating systems. Names that are used in C code are case sensitive as well as MACRO names used as short-cuts within the FDF file. Use of "/../" in a path and "./" or "../" at the start of a path is prohibited.

Note: GUID values are used during runtime to uniquely map the C names of PROTOCOLS, PPIS, PCDS and other variable names.

Note: This document uses "\" to indicate that a line that cannot be displayed in this document on a single line. Within the DSC specification, each entry must appear on a single line.

Note: The total path and file name length is limited by the operating system and third party tools. It is recommended that for EDK II builds that the project directories under a subst drive in Windows (s:/build as an example) or be located in either the /opt directory or in the user's /home/username directory for Linux and OS/X. This will minimize the path lengths of filenames for the command-line tools.