BitBake User Manual
Contents
1. EE bee ee ewe di ee we hee bbe ee A E PA ee ee oe Ae ee Be a SE Bee ae Ss The BitBake command 4 1 4 2 4 3 44 Introduction vu Zu e o Hh ee Bw Bie be ee a RS e ee eee wl A e Se eek we de Usage and Syntax ic ex E we RE e ee EEN Special Variables ert Ee Ee EN Se PY SR OR Ew SNR bee Ee ee Oe aw e 43 1 BB NUMBER THREADS opd 4 a ele deh ee Ba woe wR epee dd we ee he ee wee a Metadata Zi S920 ae Bee Ea bbe eRe Sign Oi OG A Gah ee Sh BES EE he Ow ww ee Se bx 10 10 10 10 10 11 11 11 ES LA 12 12 BitBake User Manual 1 17 Chapter 1 Introduction 1 1 Overview BitBake is at its simplest a tool for executing tasks and managing metadata As such its similarities to GNU make and other build tools are readily apparent It was inspired by Portage the package management system used by the Gentoo Linux distribution BitBake is the basis of the OpenEmbedded project which is being used to build and maintain a number of embedded Linux distributions projects such as Angstrom and the Yocto project 1 2 Background and goals Prior to BitBake no other build tool adequately met the needs of an aspiring embedded Linux distribution All of the buildsystems used by traditional desktop Linux distributions lacked important functionality and none of the ad hoc buildroot systems prevalent in the embedded space were scalable or maintainable Some important original goals for BitBake were Handle crosscompilatio2. be used externally too if needed The standard operations mentioned above also work on flags VARIABLE SOMEFLAG value In this example VARIABLE has a flag SOMEFLAG which is set to value 2 1 18 Inheritance NOTE This is only supported in bb and bbclass files The inherit directive is a means of specifying what classes of functionality your bb requires It is a rudimentary form of inheritance For example you can easily abstract out the tasks involved in building a package that uses autoconf and automake and put that into a bbclass for your packages to make use of A given bbclass is located by searching for classes filename bbclass in BBPATH where filename is what you inherited 2 1 19 Tasks NOTE This is only supported in bb and bbclass files In BitBake each step that needs to be run for a given bb is known as a task There is a command addtask to add new tasks must be a defined Python executable metadata and must start with do_ and describe intertask dependencies BitBake User Manual 7 17 python do_printdate import time print time strftime SYSmsd time gmtime addtask printdate before do_build This defines the necessary Python function and adds it as a task which is now a dependency of do_build the default task If anyone executes the do_build task that will result in do_printdate being run first 2 1 20 Task Flags Tasks support a number of flags which control v
3. file or executing a given task on a set of multiple bb files accounting for interdependencies amongst them 4 2 Usage and syntax bitbake help usage bitbake options package Executes the specified task default is build for a given set of BitBake files It expects that BBFILES is defined which is a space separated list of files to be executed BBFILES does support wildcards Default BBFILES are the bb files in the current directory options version show program s version number and exit Silo show this help message and exit b BUILDFILE buildfile BUILDFILE execute the task against this bb file rather than a package from BBFILES k continue continue as much as possible after an error While the target that failed and those that depend on it Cannot be remade the other dependencies of these targets can be processed all the same If 7 SIKO ICS force run of specified cmd regardless of stamp status iy interactiv drop into the interactive mode also called the BitBake shell O CMD AS Ema SM Specify task to execute Note that this only executes the specified task for the providee and the packages it depends on i e compile does not implicitly call stage for the dependencies IOW use only if you know what you are doing Depending on the base bbclass a listtasks task is defined and will show available tasks r FILE read FILE read th
4. finalisation time just before overrides are expanded AS B x B 2 A2 y So in this case A2 would take the value of X 2 3 Dependency handling BitBake handles dependencies at the task level since to allow for efficient operation with multiple processed executing in parallel A robust method of specifying task dependencies is therefore needed 2 3 1 Dependencies internal to the bb file Where the dependencies are internal to a given bb file the dependencies are handled by the previously detailed addtask directive 2 3 2 Build Dependencies DEPENDS lists build time dependencies The deptask flag for tasks is used to signify the task of each item listed in DEPENDS which must have completed before that task can be executed do_configure deptask do_populate_staging means the do_populate_staging task of each item in DEPENDS must have completed before do_configure can execute 2 3 3 Runtime Dependencies The PACKAGES variable lists runtime packages and each of these can have RDEPENDS and RRECOMMENDS runtime de pendencies The rdeptask flag for tasks is used to signify the task of each item runtime dependency which must have completed before that task can be executed do_package_write rdeptask do_package means the do_package task of each item in RDEPENDS must have completed before do_package_write can execute 2 3 4 Recursive Dependencies These are specified with the recrdeptask flag which is
5. such as base bbclass can be removed from the graph bitbake g blah bitbake g I virtual whatever I bloom blah 4 3 Special variables Certain variables affect BitBake operation 4 3 1 BB _NUMBER_THREADS The number of threads BitBake should run at once default 1 4 4 Metadata As you may have seen in the usage information or in the information about bb files the BBF ILES variable is how the BitBake tool locates its files This variable is a space separated list of files that are available and supports wildcards Example 4 4 Setting BBFILES BBFILES path to bbfiles bb With regard to dependencies it expects the bb to define a DEPENDS variable which contains a space separated list of package names which themselves are the PN variable The PN variable is in general set to a component of the bb filename by default Example 4 5 Depending on another bb a bb PN package a DEPENDS package b b bb PN package b BitBake User Manual 17 17 Example 4 6 Using PROVIDES This example shows the usage of the PROVIDES variable which allows a given bb to specify what functionality it provides packagel bb PROVIDES virtual package package2 bb DEPENDS virtual package package3 bb PROVIDES virtual package As you can see we have two different bb s that provide the same functi
6. to the above A will be set to someothervalue This is a lazy weak assignment in that the assignment does not occur until the end of the parsing process so that the last rather than the first assignment to a given variable will be used Any other setting of A using or will however override the value set with 2 1 5 Immediate variable expansion results in a variable s contents being expanded immediately rather than when the variable is actually used T hss A S B S A test S T T 456 B el C cval C S C append In that example A would contain test 123 B would contain 456 bval and C would be cvalappend 2 1 6 Appending and prepending bval additionaldata Eva test toy os Il ze In this example Bis now bval additionaldata and Cistest cval 2 1 7 Appending and prepending without spaces val additionaldata Mora MIS yey lud oy ll In this example B is now bvaladditionaldata and C is testcval In contrast to the above appending and prepending operators no additional space will be introduced 2 1 8 Appending and Prepending override style syntax BE ee tion cule B_append additional data Veal C_prepend additional data This example results in B becoming bval additional data and C becoming additional data cval Note the spaces in the append Unlike the operator additional space is not automati
7. used signify the task s of dependencies which must have completed before that task can be executed It works by looking though the build and runtime dependencies of the current recipe as well as any inter task dependencies the task has then adding a dependency on the listed task It will then recurse through the dependencies of those tasks and so on It may be desireable to recurse not just through the dependencies of those tasks but through the build and runtime dependencies of dependent tasks too If that is the case the taskname itself should be referenced in the task list e g do_a recrdeptask do_a do bi BitBake User Manual 10 17 2 3 5 Inter task The depends flag for tasks is a more generic form of which allows an interdependency on specific tasks rather than specifying the data in DEPENDS do_patch depends quilt native do_populate_staging means the do_populate_staging task of the target quilt native must have completed before the do_patch can execute The rdepends flag works in a similar way but takes targets in the runtime namespace instead of the build time dependency namespace 2 4 Parsing 2 4 1 Configuration files The first kind of metadata in BitBake is configuration metadata This metadata is global and therefore affects all packages and tasks which are executed BitBake will first search the current working directory for an optional conf bblayers conf configuration file This file is ex pe
8. BitBake User Manual BitBake User Manual BitBake User Manual Copyright O 2004 2005 2006 2011 Chris Larson Phil Blundell Richard Purdie This work is licensed under the Creative Commons Attribution License To view a copy of this license visit http creativecommons org licenses by 2 5 or send a letter to Creative Commons 559 Nathan Abbott Way Stanford California 94305 USA BitBake User Manual Contents 1 Introduction 1 1 1 2 OVERVIEW s amp ea A 4 e ae E e E E A ee e a OR die aa Se dea Background and goals ee 2 Metadata 2 1 2 2 DESEN eg E Aa a a Arte ae Se ee eas 2 1 1 Basic variable setting sois eae pa E a a a da ELE e 2 1 2 Variable expansion 2 1 3 Setting a detault value a0 e a e a da a 2 1 4 Setting a weak default value ee ee 2 1 5 Immediate variable expansion a 2 1 6 Appending and prepending Gi 2 1 7 Appending and prepending without spaces 2 2 ee ee ee 2 1 8 Appending and Prepending override style syntax o o e e 2 1 9 Removing override style syntax 2 1 10 Conditional metadata set lt s s s ccce aoaaa a e a e a e e a OR 2 1 11 Conditional aprende 2 1 12 IMCI SION e iaa laa oe ee a ar A 2 1 13 Requiting ClUSION cx EEN ENEE as e aa a a AA E 2 1 14 Python variable expansion 2 1 15 Defining executable metadata oaoa ee 2 1 16 Defining Python functions into the global Python namesp
9. ECOMMAND_cvs DL_DIR specifies where a temporary checkout is saved SRCDATE specifies which date to use when doing the fetching the special value of now will cause the checkout to be updated on every build FETCHCOMMAND and UPDATECOMMAND specify which executables to use for the CVS checkout or update The supported parameters are module tag date method localdir rsh and scmdata The module specifies which module to check out the tag describes which CVS TAG should be used for the checkout By default the TAG is empty A date can be specified to override the SRCDATE of the configuration to checkout a specific date The special value of now will cause the checkout to be updated on every build met hod is by default pserver If ext is used the rsh parameter will be evaluated and CVS_RSH will be set Finally localdir is used to checkout into a special directory relative to CVSDIR SRC_URI cvs CVSROOT module mymodule tag some version method ext SRC_URI cvs CVSROOT module mymodule date 20060126 localdir usethat 3 4 HTTP FTP fetcher The URNs for the HTTP FTP fetcher are http https and ftp This fetcher honors the variables FETCHCOMMAND_wget FETC HCOMMAND contains the command used for fetching URI and FILES will be replaced by the URI and basename of the file to be fetched SRC_URI http oe handhelds org not_there aac SRC_URI ftp oe handhelds org not_there_as_well aac SRC
10. _URI ftp you oe handheld sorg home you secret plan 3 5 SVN fetcher The URN for the SVN fetcher is svn This fetcher honors the variables FETCHCOMMAND_svn SVNDIR SRCREV FETCHCOMMAND contains the subversion com mand SRCREV specifies which revision to use when doing the fetching The supported parameters are proto rev and scmdata proto is the Subversion protocol rev is the Subversion revision If scmdata is set to keep the svn directories will be available during compile time SRC_URI SRESU RE svn svn oe handhelds org svn module vip proto http rev 667 svn svn oe handhelds org svn module opie proto svntssh date 20060126 3 6 GIT fetcher The URN for the GIT Fetcher is git The variable GITDIR will be used as the base directory where the git tree is cloned to The parameters are tag protocol and scmdata tag is a Git tag the default is master protocol is the Git protocol to use and defaults to git if a hostname is set otherwise its file If semdata is set to keep the at directory will be available during compile time BitBake User Manual 13 17 SRC_URI git git oe handhelds org git vip git tag version 1 SRC_URI git git oe handhelds org git vip git protocol http BitBake User Manual 14 17 Chapter 4 The BitBake command 4 1 Introduction bitbake is the primary command in the system It facilitates executing tasks in a single bb
11. ace o oo o 2 117 Variable flags 2 A EE tr a A EN e e X 21 58 Inheritance s cono i a aa E e al e a Be SEN KT EENHEETEN 21 20 Task Flags 2 2k weer kit Bobet ra BS a eS 48 212 EVENS ss ea doe a a ee eee wa ea a eal be ew ee E 2 14 22 Vanants gon ar ee HE RR SN ee ea ee bos Pw ee eee ES e Variable interaction Worked Examples 0 000 a 2 2 1 Override and append ordering BitBake User Manual 2 3 2 4 2226 Key Expansion se x A eena 42 A A ee a e Dependency handling gs apace Ne SORE a GOS RS SR OR SE ASG Be a be OS Beg Se oS 2 3 1 Dependencies internal tothe bb file o o e e 0000000000 23 2 Build Dependencies ve ssns peaa tee e a eee ee oS 2 3 3 Runtime Dependencies ENEE EE ee A ee a ee ee e 2 3 4 Recursive Dependencies EEN E 23 0 Jnter task mios E Seca e HERR ee ed E sy Ree E e PASOS A kh EO GS BP a S Ee RS GR Ee As Oe Be Oe Ae eg eB 24 1 Configuration files s s serce 542208 00h eee Pee he eee eee eee ee Eee ES DAD Clageg a ee A EE Re we Ol ale D eal ea Ee Bee A ae ee E E 243 DOMMES a RS Be ee Ee eS SER Rae EG RGR R SE A ee SS File download support 3 1 3 2 3 3 3 4 3 5 3 6 OVERVIEW us Sed e e dee Sete Se E A RRA RT Ee oe e ae e be Ea Local file fetchet e 2 haw EE ee eb ba woe eee be en Sad wh PEER EEA we we CVS Teicher inet E Beets e PR amor EE Ret eae Ss HTTP FTP feteher i eae Get See See we RES RE Eee eae Rede ox SVN TELCEL co
12. anage multiple bb files Clearly there needs to be a way to tell BitBake what files are available and of those which we want to execute at this time There also needs to be a way for each bb to express its dependencies both for build time and runtime There must be a way for the user to express their preferences when multiple bb s provide the same functionality or when there are multiple versions of a bb The next section Metadata outlines how to specify such things Note that the bitbake command when not using buildfile accepts a PROVIDER not a filename or anything else By default a bb generally PROVIDES its packagename packagename version and packagename version revision bitbake blah SOHO ae kel 0 bitbake blah 1 0 r0 S bitbake c clean blah bitbake virtual whatever S bitbake c clean virtual whatever BitBake User Manual 16 17 Example 4 3 Generating dependency graphs BitBake is able to generate dependency graphs using the dot syntax These graphs can be converted to images using the dot application from Graphviz Two files will be written into the current working directory depends dot containing dependency information at the package level and task depends dot containing a breakdown of the dependencies at the task level To stop depending on common depends one can use the I depend to omit these from the graph This can lead to more readable graphs This way DEPENDS from inherited classes
13. ant upstream Usage BBFILES stuff openembedded x x bb stuff openembedded modified x x bb BBFILE_COLLECTIONS upstream local BBFILE_PATTERN_upstream stuff openembedded BBFILE_PATTERN_local stuff openembedded modified BBFILE_PRIORITY_upstream 5 IESELEN EE EECH oO AO
14. arious functionality of the task These are as follows dirs directories which should be created before the task runs cleandirs directories which should be created before the task runs but should be empty noexec marks the tasks as being empty and no execution required These are used as dependency placeholders or used when added tasks need to be subsequently disabled nostamp don t generate a stamp file for a task This means the task is always rexecuted fakeroot this task needs to be run in a fakeroot environment obtained by adding the variables in FAKEROOTENV to the environment gt umask the umask to run the task under For the deptask rdeptask depends rdepends and recrdeptask flags please see the dependencies section 2 1 21 Events NOTE This is only supported in bb and bbclass files BitBake allows installation of event handlers Events are triggered at certain points during operation such as the beginning of operation against a given bb the start of a given task task failure task success et cetera The intent is to make it easy to do things like email notification on build failure addhandler myclass_eventhandler python myclass_eventhandler from bb event import getName from bb import data print The name of the Event is Sait getName e print The file we run for is Sait data getVar FILE e data True This event handler gets
15. cal downloaded output is placed into the directory specified by the DL_DIR For non local archive downloads the code can verify sha256 and md5 checksums for the download to ensure the file has been downloaded correctly These may be specified either in the form SRC_URI md5sum for the md5 checksum and SRC_URI sha256sum for the sha256 checksum or as pa rameters on the SRC_URI such as SRC_URI http example com foobar tar bz2 md5sum 4a8e0f237e96 1 fd7785d19d07fdb994d If BB_STRICT_CHECKSUM is set any download without a checksum will trigger an error message In cases where multiple files are listed in SRC_URL the name parameter is used assign names to the urls and these are then specified in the checksums in the form SRC_URI name sha256sum 3 2 Local file fetcher The URN for the local file fetcher is file The filename can be either absolute or relative If the filename is relative FILESPATH and failing that FILESDIR will be used to find the appropriate relative file The metadata usually extend these variables to include variations of the values in OVERRIDES Single files and complete directories can be specified BitBake User Manual 12 17 SRC_URI file relativefile patch SRC_URI file relativefile patch this ignored SRC_URI file Users ich very_important_software 3 3 CVS fetcher The URN for the CVS fetcher is cvs This fetcher honors the variables CVSDIR SRCDATE FETCHCOMMAND_cvs UPD AT
16. called every time an event is triggered A global variable e is defined e data contains an instance of bb data With the getName e method one can get the name of the triggered event The above event handler prints the name of the event and the content of the FILE variable 2 1 22 Variants Two BitBake features exist to facilitate the creation of multiple buildable incarnations from a single recipe file The first is BBCLASSEXTEND This variable is a space separated list of classes used to extend the recipe for each variant As an example setting BBCLASSEXTEND native BitBake User Manual 8 17 results in a second incarnation of the current recipe being available This second incarnation will have the native class inherited The second feature is BBVERSIONS This variable allows a single recipe to build multiple versions of a project from a single recipe file and allows you to specify conditional metadata using the OVERRIDES mechanism for a single version or an optionally named range of versions BBEVERSTONS OZ SRC_URI_git git someurl somepath git BBVERSIONS 1 0 0 6 1 0 0 LO 17 91 2105 7a SRC_URI_append_1 0 7 file some_patch_which_the_new_versions_need patch patch 1 Note that the name of the range will default to the original version of the recipe so given OE a recipe file of foo_1 0 0 bb will default the name of its versions to 1 0 0 This is usefu
17. cally added You must take steps to add space yourself BitBake User Manual 5 17 2 1 9 Removing override style syntax FOO 123 456 789 123456 123 456 123 456 FOO_remove 123 FOO_remove 456 In this example FOO is now 789 123456 2 1 10 Conditional metadata set OVERRIDES is a separated variable containing each item you want to satisfy conditions So if you have a variable which is conditional on arm and arm is in OVERRIDES then the arm specific version of the variable is used rather than the non conditional version Example OVERRIDES architecture os machine EST defaultvalue EST_os osspecificvalue EST_condnotinoverrides othercondvalue In this example TEST would be osspecificvalue due to the condition os being in OVERRIDES 2 1 11 Conditional appending BitBake also supports appending and prepending to variables based on whether something is in OVERRIDES Example DEPENDS glibc ncurses OVERRIDES machine local DEPENDS_append_machine libmad In this example DEPENDS is set to glibc ncurses libmad 2 1 12 Inclusion Next there is the include directive which causes BitBake to parse whatever file you specify and insert it at that location which is not unlike make However if the path specified on the include line is a relative path BitBake will locate the firs
18. cted to contain a BBLAYERS variable which is a space delimited list of layer directories For each directory in this list a conf layer conf file will be searched for and parsed with the LAYERDIR variable being set to the directory where the layer was found The idea is these files will setup BBPATH and other variables correctly for a given build directory automatically for the user BitBake will then expect to find conf bitbake conf somewhere in the user specified BBPATH That configuration file generally has include directives to pull in any other metadata generally files specific to architecture machine local and so on Only variable definitions and include directives are allowed in conf files 2 4 2 Classes BitBake classes are our rudimentary inheritance mechanism As briefly mentioned in the metadata introduction they re parsed when an inherit directive is encountered and they are located in classes relative to the directories in BBPATH 2 4 3 bb files A BitBake bb file is a logical unit of tasks to be executed Normally this is a package to be built Inter bb dependencies are obeyed The files themselves are located via the BBFILES variable which is set to a space separated list of bb files and does handle wildcards BitBake User Manual 11 17 Chapter 3 File download support 3 1 Overview BitBake provides support to download files this procedure is called fetching and it handled by the fetch and f
19. e specified file before bitbake conf v verbose output more chit chat to the terminal D debug Increase the debug level You can specify this more than once UA don t execute just go through the motions p parse only quit after parsing the BB files developers only BitBake User Manual 15 17 SS ON SNS OS show current and preferred versions of all packages e environment show the global or per package environment this is what used to be bbread t S Cfeeljolanyil A mit the dependency trees of the specified packages in the dot syntax L IGNORED DOT _DEPS ignore deps IGNORED_DOT_DEPS Stop processing at the given list of dependencies when generating dependency graphs This can help to make the graph more appealing 1 DEBUG_DOMAINS log domains DEBUG_DOMAINS Show debug logging for the specified logging domains P DiO9k ee profile the command and print a report Example 4 1 Executing a task against a single bb Executing tasks for a single file is relatively simple You specify the file in question and BitBake parses it and executes the specified task or build by default It obeys intertask dependencies when doing so clean task bitbake b blah_1 0 bb c clean build task bitbake D blah_1 0 bb Example 4 2 Executing tasks against a set of bb files There are a number of additional complexities introduced when one wants to m
20. etch2 modules At this point the original fetch code is considered to be replaced by fetch2 and this manual only related to the fetch2 codebase The SRC_URI is normally used to tell BitBake which files to fetch The next sections will describe the available fetchers and their options Each fetcher honors a set of variables and per URI parameters separated by a consisting of a key and a value The semantics of the variables and parameters are defined by the fetcher BitBake tries to have consistent semantics between the different fetchers The overall fetch process is that first fetches are attempted from PREMIRRORS If those don t work the original SRC_URI is attempted and if that fails BitBake will fall back to MIRRORS Cross urls are supported so its possible to mirror a git repository on an http server as a tarball for example Some example commonly used mirror definitions are PREMIRRORS ES y Sl ot http somemirror org sources An SUSE http somemirror org sources An JE A at http somemirror org sources An LE AE http somemirror org sources An DESEAS http somemirror org sources n AC oid ots http somemirror org sources n Sykes Pf ose ot http somemirror org sources n svn http somemirror org sources n MIRRORS REISS ate ot http somemirror org sources n ICIS d A at or http somemirror org sources n EE aa een http somemirror org sources n Non lo
21. l as the range name is not only placed into overrides it s also made available for the metadata to use in the form of the BPV variable for use in file search paths FILESPATH 2 2 Variable interaction Worked Examples Despite the documentation of the different forms of variable definition above it can be hard to work out what happens when variable operators are combined This section documents some common questions people have regarding the way variables interact 2 2 1 Override and append ordering There is often confusion about which order overrides and the various append operators take effect OVERRIDES foo A_foo_append xX In this case X is unconditionally appended to the variable A_foo Since foo is an override A_foo would then replace A OVERRIDES foo A X A append_foo Y In this case only when foo is in OVERRIDES Y is appended to the variable A so the value of A would become XY NB no spaces are appended OVERRIDES foo A_foo_append Xx A_foo_append Y This behaves as per the first case above but the value of A would be X Y instead of just X A In A_append 2 A_append 3 A 4 A 5 Would ultimately result in A taking the value 1 4523 since the _append operator executes at the same time as the expansion of other overrides BitBake User Manual 9 17 2 2 2 Key Expansion Key expansion happens at the data store
22. n Handle interpackage dependencies build time on target architecture build time on native architecture and runtime Support running any number of tasks within a given package including but not limited to fetching upstream sources unpack ing them patching them configuring them et cetera Must be Linux distribution agnostic both build and target Must be architecture agnostic Must support multiple build and target operating systems including Cygwin the BSDs etc Must be able to be self contained rather than tightly integrated into the build machine s root filesystem There must be a way to handle conditional metadata on target architecture operating system distribution machine It must be easy for the person using the tools to supply their own local metadata and packages to operate against Must make it easy to collaborate between multiple projects using BitBake for their builds Should provide an inheritance mechanism to share common metadata between many packages Over time it has become apparent that some further requirements were necessary e Handle variants of a base recipe native sdk multilib BitBake User Manual 2 17 e Able to split metadata into layers and allow layers to override each other e Allow representation of a given set of input variables to a task as a checksum e based on that checksum allow acceleration of builds with prebuilt components BitBake satisfies all the original re
23. onality virtual package Clearly there needs to be a way for the person running BitBake to control which of those providers gets used There is indeed such a way The following would go into a conf file to select packagel PREFERRED_PROVIDER_virtual package packagel Example 4 7 Specifying version preference When there are multiple versions of a given package BitBake defaults to selecting the most recent version unless otherwise specified If the bb in question has a DEFAULT_PREFERENCE set lower than the other bb s default is 0 then it will not be selected This allows the person or persons maintaining the repository of bb files to specify their preference for the default selected version In addition the user can specify their preferred version If the first bb is named a_1 1 bb then the PN variable will be set to a and the PV variable will be set to 1 1 If we then have an a_1 2 bb BitBake will choose 1 2 by default However if we define the following variable in a conf that BitBake parses we can change that PREFERRED_VERSION_a 1 1 Example 4 8 Using bbfile collections bbfile collections exist to allow the user to have multiple repositories of bbfiles that contain the same exact package For example one could easily use them to make one s own local copy of an upstream repository but with custom modifications that one does not w
24. quirements and many more with extensions being made to the basic functionality to reflect the addition requirements Flexibility and power have always been the priorities It is highly extensible supporting embedded Python code and execution of any arbitrary tasks BitBake User Manual 3 17 Chapter 2 Metadata 2 1 Description BitBake metadata can be classified into 3 major areas e Configuration Files e bb Files e Classes What follows are a large number of examples of BitBake metadata Any syntax which isn t supported in any of the aforemen tioned areas will be documented as such 2 1 1 Basic variable setting VARIABLE value In this example VARIABLE is value 2 1 2 Variable expansion BitBake supports variables referencing one another s contents using a syntax which is similar to shell scripting A aval B preS A post This results in A containing aval and B containing preavalpost 2 1 3 Setting a default value A aval If A is set before the above is called it will retain its previous value If A is unset prior to the above call A will be set to aval Note that this assignment is immediate so if there are multiple assignments to a single variable the first of those will be used BitBake User Manual 4 17 2 1 4 Setting a weak default value A somevalue A someothervalue If A is set before the above it will retain that value If A is unset prior
25. t one it can find within BBPATH 2 1 13 Requiring inclusion In contrast to the include directive require will raise an ParseError if the file to be included cannot be found Otherwise it will behave just like the include directive 2 1 14 Python variable expansion DATE S time strftime YsmSd time gmtime This would result in the DATE variable containing today s date BitBake User Manual 6 17 2 1 15 Defining executable metadata NOTE This is only supported in bb and bbclass files do_mytask echo Hello world This is essentially identical to setting a variable except that this variable happens to be executable shell code python do_printdate import time print time strftime SY sm d time gmtime This is the similar to the previous but flags it as Python so that BitBake knows it is Python code 2 1 16 Defining Python functions into the global Python namespace NOTE This is only supported in bb and bbclass files def get_depends bb d if d getVar SOMECONDITION True return dependencywithcond else return dependency SOMECONDITION 1 DEPENDS S get_depends bb d This would result in DEPENDS containing dependencywithcond 2 1 17 Variable flags Variables can have associated flags which provide a way of tagging extra information onto a variable Several flags are used internally by BitBake but they can
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