2 DSC Overview

This section of the document provides an overview to processing EDK II platform description (DSC) file. Additional chapters describe different sections of the EDK II DSC file in detail.

EDK II parsing tools contain the templates for processing files to create the component binary images from source files. EDK II Binary Modules are not required to be included in EDK II DSC files (they must be included if the Binary Module uses PCDs that use PatchableInModule or DynamicEx PCD access methods). EDK II DSC files are a list of:

  • EDK II Module INF Files
  • EDK Components
  • EDK libraries (only used by EDK Components)
  • EDK II Library Class Instance Mappings (only used by EDK II Modules)
  • EDK II PCD Entries

There are no new features or format introduced in this specification.

DSC files that use any new features must use the new DSC_SPECIFICATION = 0x0001001C in the [Defines] section. Older DSC files that do not use any of these features do not need to update the DSC_SPECIFICATION value.

This version of the specification reflects changes to the EDK II reference build system that has been updated to support builds using EDK II Packages that are located in directories outside of the directory specified by the system environment variable, WORKSPACE.

An EDK II Package (directory) is a directory that contains an EDK II package declaration (DEC) file.

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.

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 DSC are case-sensitive in order to support building on UNIX style operating systems. Use of "/../" in a path and, "./" or "../" at the start of a path is prohibited.

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 WORKSPACE (or directories listed in the PACKAGESPATH system environment variable) directory be either a directory 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.