6.1. Parsing

-6.1. Parsing

- BitBake parses configuration files, classes, and .bb files. -

- The first thing BitBake does is look for the bitbake.conf file. - This file resides in the - Source Directory - within the meta/conf/ directory. - BitBake finds it by examining its - BBPATH environment - variable and looking for the meta/conf/ - directory. -

- The bitbake.conf file lists other configuration - files to include from a conf/ - directory below the directories listed in BBPATH. - In general, the most important configuration file from a user's perspective - is local.conf, which contains a user's customized - settings for the OpenEmbedded build environment. - Other notable configuration files are the distribution - configuration file (set by the - DISTRO variable) - and the machine configuration file - (set by the - MACHINE variable). - The DISTRO and MACHINE BitBake environment - variables are both usually set in - the local.conf file. - Valid distribution - configuration files are available in the meta/conf/distro/ directory - and valid machine configuration - files in the meta/conf/machine/ directory. - Within the meta/conf/machine/include/ - directory are various tune-*.inc configuration files that provide common - "tuning" settings specific to and shared between particular architectures and machines. -

- After the parsing of the configuration files, some standard classes are included. - The base.bbclass file is always included. - Other classes that are specified in the configuration using the - INHERIT - variable are also included. - Class files are searched for in a classes subdirectory - under the paths in BBPATH in the same way as - configuration files. -

- After classes are included, the variable - BBFILES - is set, usually in - local.conf, and defines the list of places to search for - .bb files. - By default, the BBFILES variable specifies the - meta/recipes-*/ directory within Poky. - Adding extra content to BBFILES is best achieved through the use of - BitBake layers as described in the - "Understanding and - Creating Layers" section of the Yocto Project Development Manual. -

- BitBake parses each .bb file in BBFILES and - stores the values of various variables. - In summary, for each .bb - file the configuration plus the base class of variables are set, followed - by the data in the .bb file - itself, followed by any inherit commands that - .bb file might contain. -

- Because parsing .bb files is a time - consuming process, a cache is kept to speed up subsequent parsing. - This cache is invalid if the timestamp of the .bb - file itself changes, or if the timestamps of any of the include, - configuration or class files the .bb - file depends on changes. -