6.2. Preferences and Providers

-6.2. Preferences and Providers

- Once all the .bb files have been - parsed, BitBake starts to build the target (core-image-sato - in the previous section's example) and looks for providers of that target. - Once a provider is selected, BitBake resolves all the dependencies for - the target. - In the case of core-image-sato, it would lead to - packagegroup-core-x11-sato, - which in turn leads to recipes like matchbox-terminal, - pcmanfm and gthumb. - These recipes in turn depend on eglibc and the toolchain. -

- Sometimes a target might have multiple providers. - A common example is "virtual/kernel", which is provided by each kernel package. - Each machine often selects the best kernel provider by using a line similar to the - following in the machine configuration file: -

-     PREFERRED_PROVIDER_virtual/kernel = "linux-yocto"
-

- The default PREFERRED_PROVIDER - is the provider with the same name as the target. -

- Understanding how providers are chosen is made complicated by the fact - that multiple versions might exist. - BitBake defaults to the highest version of a provider. - Version comparisons are made using the same method as Debian. - You can use the - PREFERRED_VERSION - variable to specify a particular version (usually in the distro configuration). - You can influence the order by using the - DEFAULT_PREFERENCE - variable. - By default, files have a preference of "0". - Setting the DEFAULT_PREFERENCE to "-1" makes the - package unlikely to be used unless it is explicitly referenced. - Setting the DEFAULT_PREFERENCE to "1" makes it likely the package is used. - PREFERRED_VERSION overrides any DEFAULT_PREFERENCE setting. - DEFAULT_PREFERENCE is often used to mark newer and more experimental package - versions until they have undergone sufficient testing to be considered stable. -

- In summary, BitBake has created a list of providers, which is prioritized, for each target. -