The eCos Component Writer's Guide

Bart Veer

John Dallaway

Table of Contents
1. Overview
Component Framework
Configuration Option
Component Repository
Why Configurability?
Approaches to Configurability
Degrees of Configurability
2. Package Organization
Packages and the Component Repository
Package Versioning
Package Contents and Layout
Outline of the Build Process
Configurable Source Code
Exported Header Files
Package Documentation
Test Cases
Host-side Support
Making a Package Distribution
The eCos package distribution file format
Preparing eCos packages for distribution
3. The CDL Language
Language Overview
CDL Commands
CDL Properties
Information-providing Properties
The Configuration Hierarchy
Value-related Properties
Generating the Configuration Header Files
Controlling what gets Built
Miscellaneous Properties
Option Naming Convention
An Introduction to Tcl
Values and Expressions
Option Values
Ordinary Expressions
Goal Expressions
List Expressions
Updating the ecos.db database
4. The Build Process
Build Tree Generation
Configuration Header File Generation
Building eCos
Updating the Build Tree
Exporting Public Header Files
Generating the Libraries
The extras.o file
Compilers and Flags
Custom Build Steps
Startup Code
The Linker Script
Building Test Cases
5. CDL Language Specification
cdl_option — Define a single configuration option
cdl_component — Define a component, a collection of configuration options
cdl_package — Define a package, a component that can be distributed
cdl_interface — Define an interface, functionality that can be provided by a number of different implementations.
active_if — Allow additional control over the active state of an option or other CDL entity.
calculated — Used if the current option's value is not user-modifiable, but is calculated using a suitable CDL expression.
compile — List the source files that should be built if this option is active and enabled.
default_value — Provide a default value for this option using a CDL expression.
define — Specify additional #define symbols that should go into the owning package's configuration header file.
define_format — Control how an option's value will appear in the configuration header file.
define_header — Specify the configuration header file that will be generated for a given package.
define_proc — Use a fragment of Tcl code to output additional data to configuration header files.
description — Provide a textual description for an option.
display — Provide a short string describing this option.
doc — The location of online-documentation for a configuration option.
flavor — Specify the nature of a configuration option.
hardware — Specify that a package is tied to specific hardware.
if_define — Output a common preprocessor construct to a configuration header file.
implements — Enabling this option provides one instance of a more general interface.
include_dir — Specify the desired location of a package's exported header files in the install tree.
include_files — List the header files that are exported by a package.
legal_values — Impose constraints on the possible values for an option.
library — Specify which library should contain the object files generated by building this package.
make — Define an additional custom build step associated with an option, resulting in a target that should not go directly into a library.
make_object — Define a custom build step, resulting in an object file that should go into a library.
no_define — Suppress the normal generation of a preprocessor #define symbol in a configuration header file.
parent — Control the location of an option in the configuration hierarchy.
requires — List constraints that the configuration should satisfy if a given option is active and enabled..
script — Include additional configuration information from another CDL script.
6. Templates, Targets and Other Topics