Preferring and providing recipes

The dependency relation between recipes is core to BitBake and the build tool as a whole. It is defined inside each recipe file, with a variable which describes on what a recipe depends (DEPENDS) and what a recipe provides to the system (PROVIDES). These two variables together build the dependency graph used by BitBake during the dependency resolution.

So, if a recipe foo_1.0.bb depends on bar, BitBake lists all recipes providing bar. The bar dependency can be satisfied by the following:

• The bar_<version>.bb format as every recipe provides itself

• A recipe with the PROVIDES variable set to bar

A dependency can be satisfied by several recipes (for example, two or more recipes have PROVIDES += "bar"). In this case, we must inform BitBake the provider to use.

The virtual/kernel provider is a clear example where this mechanism is used. The virtual/ namespace is the convention adopted when we have a set of commonly overridden providers.

All recipes that require...