Configuration Items

Configuration items are the individual entities that form a configuration. Each item corresponds to the setting of a C pre-processor macro (for example, CYGHWR_HAL_ARM_PID_GDB_BAUD). The code of eCos itself is written to test such pre-processor macros so as to tailor the code. User code can do likewise.

Configuration items come in the following flavors:

Like packages, configuration items exist in a tree-based hierarchy: each configuration item has a parent which may be another configuration item or a package. Under some conditions (such as when packages are added or removed from a configuration), items may be “re-parented” such that their position in the tree changes.


Expressions are relationships between CDL items. There are three types of expression in CDL:


Each configuration item has a set of properties. The following table describes the most commonly used:

A complete description of properties is contained in the Component Writer’s Guide.

Inactive Items

Descendants of an item that is disabled are inactive: their values may not be changed. Items may also become inactive if an active_if expression is used to make the item dependent on an expression involving other items.