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authorBrandon Stafford <brandon@pingswept.org>2011-06-22 15:30:26 (GMT)
committerRichard Purdie <richard.purdie@linuxfoundation.org>2011-06-22 15:57:31 (GMT)
commit5fbb1b77d094776c587ad66d367271c0c553a889 (patch)
tree75d53a29aab066f318e7fd33bf8b0424d5d4b84b /bitbake/doc
parent3c1a9608564df94aa33611021e5587e7d6b6741b (diff)
downloadpoky-5fbb1b77d094776c587ad66d367271c0c553a889.tar.gz
doc/usermanual.xml: Tweaks for the manual
This patch contains what I hope are non-controversial improvements to the manual. Most of the changes are single characters, but the line-by-line diff makes the patch look large. (Bitbake rev: 5481cc90645e13c4e3cdea41e8e369528a0b1649) Signed-off-by: Brandon Stafford <brandon@pingswept.org> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Diffstat (limited to 'bitbake/doc')
-rw-r--r--bitbake/doc/manual/usermanual.xml133
1 files changed, 66 insertions, 67 deletions
diff --git a/bitbake/doc/manual/usermanual.xml b/bitbake/doc/manual/usermanual.xml
index 2ebdf32..7dea949 100644
--- a/bitbake/doc/manual/usermanual.xml
+++ b/bitbake/doc/manual/usermanual.xml
@@ -29,7 +29,7 @@ tasks and managing metadata. As such, its similarities to GNU make and other
29build 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 <ulink url="http://www.openembedded.org/">OpenEmbedded</ulink> project, which is being used to build and maintain a number of embedded Linux distributions, including OpenZaurus and Familiar.</para> 29build 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 <ulink url="http://www.openembedded.org/">OpenEmbedded</ulink> project, which is being used to build and maintain a number of embedded Linux distributions, including OpenZaurus and Familiar.</para>
30 </section> 30 </section>
31 <section> 31 <section>
32 <title>Background and Goals</title> 32 <title>Background and goals</title>
33 <para>Prior to BitBake, no other build tool adequately met 33 <para>Prior to BitBake, no other build tool adequately met
34the needs of an aspiring embedded Linux distribution. All of the 34the needs of an aspiring embedded Linux distribution. All of the
35buildsystems used by traditional desktop Linux distributions lacked 35buildsystems used by traditional desktop Linux distributions lacked
@@ -42,9 +42,9 @@ embedded space, were scalable or maintainable.</para>
42 <listitem><para>Handle crosscompilation.</para></listitem> 42 <listitem><para>Handle crosscompilation.</para></listitem>
43 <listitem><para>Handle interpackage dependencies (build time on target architecture, build time on native architecture, and runtime).</para></listitem> 43 <listitem><para>Handle interpackage dependencies (build time on target architecture, build time on native architecture, and runtime).</para></listitem>
44 <listitem><para>Support running any number of tasks within a given package, including, but not limited to, fetching upstream sources, unpacking them, patching them, configuring them, et cetera.</para></listitem> 44 <listitem><para>Support running any number of tasks within a given package, including, but not limited to, fetching upstream sources, unpacking them, patching them, configuring them, et cetera.</para></listitem>
45 <listitem><para>Must be linux distribution agnostic (both build and target).</para></listitem> 45 <listitem><para>Must be Linux distribution agnostic (both build and target).</para></listitem>
46 <listitem><para>Must be architecture agnostic</para></listitem> 46 <listitem><para>Must be architecture agnostic</para></listitem>
47 <listitem><para>Must support multiple build and target operating systems (including cygwin, the BSDs, etc).</para></listitem> 47 <listitem><para>Must support multiple build and target operating systems (including Cygwin, the BSDs, etc).</para></listitem>
48 <listitem><para>Must be able to be self contained, rather than tightly integrated into the build machine's root filesystem.</para></listitem> 48 <listitem><para>Must be able to be self contained, rather than tightly integrated into the build machine's root filesystem.</para></listitem>
49 <listitem><para>There must be a way to handle conditional metadata (on target architecture, operating system, distribution, machine).</para></listitem> 49 <listitem><para>There must be a way to handle conditional metadata (on target architecture, operating system, distribution, machine).</para></listitem>
50 <listitem><para>It must be easy for the person using the tools to supply their own local metadata and packages to operate against.</para></listitem> 50 <listitem><para>It must be easy for the person using the tools to supply their own local metadata and packages to operate against.</para></listitem>
@@ -91,13 +91,13 @@ share common metadata between many packages.</para></listitem>
91 <section> 91 <section>
92 <title>Setting a default value (?=)</title> 92 <title>Setting a default value (?=)</title>
93 <para><screen><varname>A</varname> ?= "aval"</screen></para> 93 <para><screen><varname>A</varname> ?= "aval"</screen></para>
94 <para>If <varname>A</varname> is set before the above is called, it will retain it's previous value. If <varname>A</varname> is unset prior to the above call, <varname>A</varname> will be set to <literal>aval</literal>. Note that this assignment is immediate, so if there are multiple ?= assignments to a single variable, the first of those will be used.</para> 94 <para>If <varname>A</varname> is set before the above is called, it will retain its previous value. If <varname>A</varname> is unset prior to the above call, <varname>A</varname> will be set to <literal>aval</literal>. Note that this assignment is immediate, so if there are multiple ?= assignments to a single variable, the first of those will be used.</para>
95 </section> 95 </section>
96 <section> 96 <section>
97 <title>Setting a default value (??=)</title> 97 <title>Setting a default value (??=)</title>
98 <para><screen><varname>A</varname> ??= "somevalue"</screen></para> 98 <para><screen><varname>A</varname> ??= "somevalue"</screen></para>
99 <para><screen><varname>A</varname> ??= "someothervalue"</screen></para> 99 <para><screen><varname>A</varname> ??= "someothervalue"</screen></para>
100 <para>If <varname>A</varname> is set before the above, it will retain that value. If <varname>A</varname> is unset prior to the above, <varname>A</varname> will be set to <literal>someothervalue</literal>. This is a lazy version of ?=, 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.</para> 100 <para>If <varname>A</varname> is set before the above, it will retain that value. If <varname>A</varname> is unset prior to the above, <varname>A</varname> will be set to <literal>someothervalue</literal>. This is a lazy version of ??=, 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.</para>
101 </section> 101 </section>
102 <section> 102 <section>
103 <title>Immediate variable expansion (:=)</title> 103 <title>Immediate variable expansion (:=)</title>
@@ -125,7 +125,7 @@ share common metadata between many packages.</para></listitem>
125<varname>B</varname> .= "additionaldata" 125<varname>B</varname> .= "additionaldata"
126<varname>C</varname> = "cval" 126<varname>C</varname> = "cval"
127<varname>C</varname> =. "test"</screen></para> 127<varname>C</varname> =. "test"</screen></para>
128 <para>In this example, <varname>B</varname> is now <literal>bvaladditionaldata</literal> and <varname>C</varname> is <literal>testcval</literal>. In contrast to the above Appending and Prepending operators no additional space 128 <para>In this example, <varname>B</varname> is now <literal>bvaladditionaldata</literal> and <varname>C</varname> is <literal>testcval</literal>. In contrast to the above appending and prepending operators, no additional space
129will be introduced.</para> 129will be introduced.</para>
130 </section> 130 </section>
131 <section> 131 <section>
@@ -147,12 +147,12 @@ will be introduced.</para>
147 </section> 147 </section>
148 <section> 148 <section>
149 <title>Inclusion</title> 149 <title>Inclusion</title>
150 <para>Next, there is the <literal>include</literal> directive, which causes BitBake to parse in whatever file you specify, and insert it at that location, which is not unlike <command>make</command>. However, if the path specified on the <literal>include</literal> line is a relative path, BitBake will locate the first one it can find within <envar>BBPATH</envar>.</para> 150 <para>Next, there is the <literal>include</literal> directive, which causes BitBake to parse whatever file you specify, and insert it at that location, which is not unlike <command>make</command>. However, if the path specified on the <literal>include</literal> line is a relative path, BitBake will locate the first one it can find within <envar>BBPATH</envar>.</para>
151 </section> 151 </section>
152 <section> 152 <section>
153 <title>Requiring Inclusion</title> 153 <title>Requiring inclusion</title>
154 <para>In contrast to the <literal>include</literal> directive, <literal>require</literal> will 154 <para>In contrast to the <literal>include</literal> directive, <literal>require</literal> will
155raise an ParseError if the to be included file can not be found. Otherwise it will behave just like the <literal> 155raise an ParseError if the file to be included cannot be found. Otherwise it will behave just like the <literal>
156include</literal> directive.</para> 156include</literal> directive.</para>
157 </section> 157 </section>
158 <section> 158 <section>
@@ -171,10 +171,10 @@ include</literal> directive.</para>
171 import time 171 import time
172 print time.strftime('%Y%m%d', time.gmtime()) 172 print time.strftime('%Y%m%d', time.gmtime())
173}</screen></para> 173}</screen></para>
174 <para>This is the similar to the previous, but flags it as python so that BitBake knows it is python code.</para> 174 <para>This is the similar to the previous, but flags it as Python so that BitBake knows it is Python code.</para>
175 </section> 175 </section>
176 <section> 176 <section>
177 <title>Defining python functions into the global python namespace</title> 177 <title>Defining Python functions into the global Python namespace</title>
178 <para><emphasis>NOTE:</emphasis> This is only supported in .bb and .bbclass files.</para> 178 <para><emphasis>NOTE:</emphasis> This is only supported in .bb and .bbclass files.</para>
179 <para><screen>def get_depends(bb, d): 179 <para><screen>def get_depends(bb, d):
180 if bb.data.getVar('SOMECONDITION', d, True): 180 if bb.data.getVar('SOMECONDITION', d, True):
@@ -187,8 +187,8 @@ include</literal> directive.</para>
187 <para>This would result in <varname>DEPENDS</varname> containing <literal>dependencywithcond</literal>.</para> 187 <para>This would result in <varname>DEPENDS</varname> containing <literal>dependencywithcond</literal>.</para>
188 </section> 188 </section>
189 <section> 189 <section>
190 <title>Variable Flags</title> 190 <title>Variable flags</title>
191 <para>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 be used externally too if needed. The standard operations mentioned above also work on flags.</para> 191 <para>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 be used externally too if needed. The standard operations mentioned above also work on flags.</para>
192 <para><screen><varname>VARIABLE</varname>[<varname>SOMEFLAG</varname>] = "value"</screen></para> 192 <para><screen><varname>VARIABLE</varname>[<varname>SOMEFLAG</varname>] = "value"</screen></para>
193 <para>In this example, <varname>VARIABLE</varname> has a flag, <varname>SOMEFLAG</varname> which is set to <literal>value</literal>.</para> 193 <para>In this example, <varname>VARIABLE</varname> has a flag, <varname>SOMEFLAG</varname> which is set to <literal>value</literal>.</para>
194 </section> 194 </section>
@@ -200,19 +200,19 @@ include</literal> directive.</para>
200 <section> 200 <section>
201 <title>Tasks</title> 201 <title>Tasks</title>
202 <para><emphasis>NOTE:</emphasis> This is only supported in .bb and .bbclass files.</para> 202 <para><emphasis>NOTE:</emphasis> This is only supported in .bb and .bbclass files.</para>
203 <para>In BitBake, each step that needs to be run for a given .bb is known as a task. There is a command <literal>addtask</literal> to add new tasks (must be a defined python executable metadata and must start with <quote>do_</quote>) and describe intertask dependencies.</para> 203 <para>In BitBake, each step that needs to be run for a given .bb is known as a task. There is a command <literal>addtask</literal> to add new tasks (must be a defined Python executable metadata and must start with <quote>do_</quote>) and describe intertask dependencies.</para>
204 <para><screen>python do_printdate () { 204 <para><screen>python do_printdate () {
205 import time 205 import time
206 print time.strftime('%Y%m%d', time.gmtime()) 206 print time.strftime('%Y%m%d', time.gmtime())
207} 207}
208 208
209addtask printdate before do_build</screen></para> 209addtask printdate before do_build</screen></para>
210 <para>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.</para> 210 <para>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.</para>
211 </section> 211 </section>
212 <section> 212 <section>
213 <title>Events</title> 213 <title>Events</title>
214 <para><emphasis>NOTE:</emphasis> This is only supported in .bb and .bbclass files.</para> 214 <para><emphasis>NOTE:</emphasis> This is only supported in .bb and .bbclass files.</para>
215 <para>BitBake allows to install 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 was to make it easy to do things like email notifications on build failure.</para> 215 <para>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.</para>
216 <para><screen>addhandler myclass_eventhandler 216 <para><screen>addhandler myclass_eventhandler
217python myclass_eventhandler() { 217python myclass_eventhandler() {
218 from bb.event import getName 218 from bb.event import getName
@@ -228,20 +228,20 @@ of the event and the content of the <varname>FILE</varname> variable.</para>
228 </section> 228 </section>
229 <section> 229 <section>
230 <title>Variants</title> 230 <title>Variants</title>
231 <para>Two Bitbake features exist to facilitate the creation of multiple buildable incarnations from a single recipe file.</para> 231 <para>Two BitBake features exist to facilitate the creation of multiple buildable incarnations from a single recipe file.</para>
232 <para>The first is <varname>BBCLASSEXTEND</varname>. This variable is a space separated list of classes to utilize to "extend" the recipe for each variant. As an example, setting <screen>BBCLASSEXTEND = "native"</screen> results in a second incarnation of the current recipe being available. This second incarantion will have the "native" class inherited.</para> 232 <para>The first is <varname>BBCLASSEXTEND</varname>. This variable is a space separated list of classes used to "extend" the recipe for each variant. As an example, setting <screen>BBCLASSEXTEND = "native"</screen> results in a second incarnation of the current recipe being available. This second incarantion will have the "native" class inherited.</para>
233 <para>The second feature is <varname>BBVERSIONS</varname>. This variable allows a single recipe to be able to build multiple versions of a project from a single recipe file, and allows you to specify conditional metadata (using the <varname>OVERRIDES</varname> mechanism) for a single version, or an optionally named range of versions:</para> 233 <para>The second feature is <varname>BBVERSIONS</varname>. 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 <varname>OVERRIDES</varname> mechanism) for a single version, or an optionally named range of versions:</para>
234 <para><screen>BBVERSIONS = "1.0 2.0 git" 234 <para><screen>BBVERSIONS = "1.0 2.0 git"
235SRC_URI_git = "git://someurl/somepath.git"</screen></para> 235SRC_URI_git = "git://someurl/somepath.git"</screen></para>
236 <para><screen>BBVERSIONS = "1.0.[0-6]:1.0.0+ \ 236 <para><screen>BBVERSIONS = "1.0.[0-6]:1.0.0+ \
237 1.0.[7-9]:1.0.7+" 237 1.0.[7-9]:1.0.7+"
238SRC_URI_append_1.0.7+ = "file://some_patch_which_the_new_versions_need.patch;patch=1"</screen></para> 238SRC_URI_append_1.0.7+ = "file://some_patch_which_the_new_versions_need.patch;patch=1"</screen></para>
239 <para>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 useful, 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 <varname>BPV</varname> variable, for use in file:// search paths (<varname>FILESPATH</varname>).</para> 239 <para>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 useful, 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 <varname>BPV</varname> variable, for use in file:// search paths (<varname>FILESPATH</varname>).</para>
240 </section> 240 </section>
241 </section> 241 </section>
242 <section> 242 <section>
243 <title>Dependency Handling</title> 243 <title>Dependency handling</title>
244 <para>Bitbake 1.7.x onwards works with the metadata at the task level since this is optimal when dealing with multiple threads of execution. A robust method of specifing task dependencies is therefore needed. </para> 244 <para>BitBake 1.7.x onwards works with the metadata at the task level since this is optimal when dealing with multiple threads of execution. A robust method of specifing task dependencies is therefore needed. </para>
245 <section> 245 <section>
246 <title>Dependencies internal to the .bb file</title> 246 <title>Dependencies internal to the .bb file</title>
247 <para>Where the dependencies are internal to a given .bb file, the dependencies are handled by the previously detailed addtask directive.</para> 247 <para>Where the dependencies are internal to a given .bb file, the dependencies are handled by the previously detailed addtask directive.</para>
@@ -249,26 +249,26 @@ SRC_URI_append_1.0.7+ = "file://some_patch_which_the_new_versions_need.patch;pat
249 249
250 <section> 250 <section>
251 <title>DEPENDS</title> 251 <title>DEPENDS</title>
252 <para>DEPENDS is taken to specify build time dependencies. The 'deptask' flag for tasks is used to signify the task of each DEPENDS which must have completed before that task can be executed.</para> 252 <para>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.</para>
253 <para><screen>do_configure[deptask] = "do_populate_staging"</screen></para> 253 <para><screen>do_configure[deptask] = "do_populate_staging"</screen></para>
254 <para>means the do_populate_staging task of each item in DEPENDS must have completed before do_configure can execute.</para> 254 <para>means the do_populate_staging task of each item in DEPENDS must have completed before do_configure can execute.</para>
255 </section> 255 </section>
256 <section> 256 <section>
257 <title>RDEPENDS</title> 257 <title>RDEPENDS</title>
258 <para>RDEPENDS is taken to specify runtime dependencies. The 'rdeptask' flag for tasks is used to signify the task of each RDEPENDS which must have completed before that task can be executed.</para> 258 <para>RDEPENDS lists runtime dependencies. The 'rdeptask' flag for tasks is used to signify the task of each item listed in RDEPENDS which must have completed before that task can be executed.</para>
259 <para><screen>do_package_write[rdeptask] = "do_package"</screen></para> 259 <para><screen>do_package_write[rdeptask] = "do_package"</screen></para>
260 <para>means the do_package task of each item in RDEPENDS must have completed before do_package_write can execute.</para> 260 <para>means the do_package task of each item in RDEPENDS must have completed before do_package_write can execute.</para>
261 </section> 261 </section>
262 <section> 262 <section>
263 <title>Recursive DEPENDS</title> 263 <title>Recursive DEPENDS</title>
264 <para>These are specified with the 'recdeptask' flag and is used to signify the task(s) of each DEPENDS which must have completed before that task can be executed. It applies recursively so also, the DEPENDS of each item in the original DEPENDS must be met and so on.</para> 264 <para>These are specified with the 'recdeptask' flag and is used signify the task(s) of each DEPENDS which must have completed before that task can be executed. It applies recursively so the DEPENDS of each item in the original DEPENDS must be met and so on.</para>
265 </section> 265 </section>
266 <section> 266 <section>
267 <title>Recursive RDEPENDS</title> 267 <title>Recursive RDEPENDS</title>
268 <para>These are specified with the 'recrdeptask' flag and is used to signify the task(s) of each RDEPENDS which must have completed before that task can be executed. It applies recursively so also, the RDEPENDS of each item in the original RDEPENDS must be met and so on. It also runs all DEPENDS first too.</para> 268 <para>These are specified with the 'recrdeptask' flag and is used signify the task(s) of each RDEPENDS which must have completed before that task can be executed. It applies recursively so the RDEPENDS of each item in the original RDEPENDS must be met and so on. It also runs all DEPENDS first.</para>
269 </section> 269 </section>
270 <section> 270 <section>
271 <title>Inter Task</title> 271 <title>Inter task</title>
272 <para>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 or RDEPENDS.</para> 272 <para>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 or RDEPENDS.</para>
273 <para><screen>do_patch[depends] = "quilt-native:do_populate_staging"</screen></para> 273 <para><screen>do_patch[depends] = "quilt-native:do_populate_staging"</screen></para>
274 <para>means the do_populate_staging task of the target quilt-native must have completed before the do_patch can execute.</para> 274 <para>means the do_populate_staging task of the target quilt-native must have completed before the do_patch can execute.</para>
@@ -278,35 +278,34 @@ SRC_URI_append_1.0.7+ = "file://some_patch_which_the_new_versions_need.patch;pat
278 <section> 278 <section>
279 <title>Parsing</title> 279 <title>Parsing</title>
280 <section> 280 <section>
281 <title>Configuration Files</title> 281 <title>Configuration files</title>
282 <para>The first of the classifications of metadata in BitBake is configuration metadata. This metadata is global, and therefore affects <emphasis>all</emphasis> packages and tasks which are executed.</para> 282 <para>The first kind of metadata in BitBake is configuration metadata. This metadata is global, and therefore affects <emphasis>all</emphasis> packages and tasks which are executed.</para>
283 <para>Bitbake will first search the current working directory for an optional "conf/bblayers.conf" configuration file. This file is expected 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.</para> 283 <para>BitBake will first search the current working directory for an optional "conf/bblayers.conf" configuration file. This file is expected 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.</para>
284 <para>Bitbake will then expect to find 'conf/bitbake.conf' somewhere in the user specified <envar>BBPATH</envar>. That configuration file generally has include directives to pull in any other metadata (generally files specific to architecture, machine, <emphasis>local</emphasis> and so on.</para> 284 <para>BitBake will then expect to find 'conf/bitbake.conf' somewhere in the user specified <envar>BBPATH</envar>. That configuration file generally has include directives to pull in any other metadata (generally files specific to architecture, machine, <emphasis>local</emphasis> and so on).</para>
285 <para>Only variable definitions and include directives are allowed in .conf files.</para> 285 <para>Only variable definitions and include directives are allowed in .conf files.</para>
286 </section> 286 </section>
287 <section> 287 <section>
288 <title>Classes</title> 288 <title>Classes</title>
289 <para>BitBake classes are our rudimentary inheritance mechanism. As briefly mentioned in the metadata introduction, they're parsed when an <literal>inherit</literal> directive is encountered, and they are located in classes/ relative to the dirs in <envar>BBPATH</envar>.</para> 289 <para>BitBake classes are our rudimentary inheritance mechanism. As briefly mentioned in the metadata introduction, they're parsed when an <literal>inherit</literal> directive is encountered, and they are located in classes/ relative to the directories in <envar>BBPATH</envar>.</para>
290 </section> 290 </section>
291 <section> 291 <section>
292 <title>.bb Files</title> 292 <title>.bb files</title>
293 <para>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 <varname>BBFILES</varname> variable, which is set to a space separated list of .bb files, and does handle wildcards.</para> 293 <para>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 <varname>BBFILES</varname> variable, which is set to a space separated list of .bb files, and does handle wildcards.</para>
294 </section> 294 </section>
295 </section> 295 </section>
296 </chapter> 296 </chapter>
297 297
298 <chapter> 298 <chapter>
299 <title>File Download support</title> 299 <title>File download support</title>
300 <section> 300 <section>
301 <title>Overview</title> 301 <title>Overview</title>
302 <para>BitBake provides support to download files this procedure is called fetching. The SRC_URI is normally used to indicate BitBake which files to fetch. The next sections will describe th available fetchers and the options they have. Each Fetcher honors a set of Variables and 302 <para>BitBake provides support to download files this procedure is called fetching. 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 <quote>;</quote> 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.
303a per URI parameters separated by a <quote>;</quote> consisting of a key and a value. The semantic of the Variables and Parameters are defined by the Fetcher. BitBakes tries to have a consistent semantic between the different Fetchers.
304 </para> 303 </para>
305 </section> 304 </section>
306 305
307 <section> 306 <section>
308 <title>Local File Fetcher</title> 307 <title>Local file fetcher</title>
309 <para>The URN for the Local File Fetcher is <emphasis>file</emphasis>. The filename can be either absolute or relative. If the filename is relative <varname>FILESPATH</varname> and <varname>FILESDIR</varname> will be used to find the appropriate relative file depending on the <varname>OVERRIDES</varname>. Single files and complete directories can be specified. 308 <para>The URN for the local file fetcher is <emphasis>file</emphasis>. The filename can be either absolute or relative. If the filename is relative, <varname>FILESPATH</varname> and <varname>FILESDIR</varname> will be used to find the appropriate relative file, depending on the <varname>OVERRIDES</varname>. Single files and complete directories can be specified.
310<screen><varname>SRC_URI</varname>= "file://relativefile.patch" 309<screen><varname>SRC_URI</varname>= "file://relativefile.patch"
311<varname>SRC_URI</varname>= "file://relativefile.patch;this=ignored" 310<varname>SRC_URI</varname>= "file://relativefile.patch;this=ignored"
312<varname>SRC_URI</varname>= "file:///Users/ich/very_important_software" 311<varname>SRC_URI</varname>= "file:///Users/ich/very_important_software"
@@ -315,10 +314,11 @@ a per URI parameters separated by a <quote>;</quote> consisting of a key and a v
315 </section> 314 </section>
316 315
317 <section> 316 <section>
318 <title>CVS File Fetcher</title> 317 <title>CVS file fetcher</title>
319 <para>The URN for the CVS Fetcher is <emphasis>cvs</emphasis>. This Fetcher honors the variables <varname>DL_DIR</varname>, <varname>SRCDATE</varname>, <varname>FETCHCOMMAND_cvs</varname>, <varname>UPDATECOMMAND_cvs</varname>. <varname>DL_DIR</varname> specifies where a temporary checkout is saved, <varname>SRCDATE</varname> specifies which date to use when doing the fetching (the special value of "now" will cause the checkout to be updated on every build), <varname>FETCHCOMMAND</varname> and <varname>UPDATECOMMAND</varname> specify which executables should be used when doing the CVS checkout or update. 318 <para>The URN for the CVS fetcher is <emphasis>cvs</emphasis>. This fetcher honors the variables <varname>DL_DIR</varname>, <varname>SRCDATE</varname>, <varname>FETCHCOMMAND_cvs</varname>, <varname>UPDATECOMMAND_cvs</varname>. <varname>DL_DIR</varname> specifies where a temporary checkout is saved. <varname>SRCDATE</varname> specifies which date to use when doing the fetching (the special value of "now" will cause the checkout to be updated on every build). <varname>FETCHCOMMAND</varname> and <varname>UPDATECOMMAND</varname> specify which executables to use for the CVS checkout or update.
320 </para> 319 </para>
321 <para>The supported Parameters are <varname>module</varname>, <varname>tag</varname>, <varname>date</varname>, <varname>method</varname>, <varname>localdir</varname>, <varname>rsh</varname> and <varname>scmdata</varname>. The <varname>module</varname> specifies which module to check out, the <varname>tag</varname> describes which CVS TAG should be used for the checkout. By default the TAG is empty. A <varname>date</varname> 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.<varname>method</varname> is by default <emphasis>pserver</emphasis>, if <emphasis>ext</emphasis> is used the <varname>rsh</varname> parameter will be evaluated and <varname>CVS_RSH</varname> will be set. Finally <varname>localdir</varname> is used to checkout into a special directory relative to <varname>CVSDIR</varname>. If <varname>scmdata</varname> is set to <quote>keep</quote> 320 <para>The supported parameters are <varname>module</varname>, <varname>tag</varname>, <varname>date</varname>, <varname>method</varname>, <varname>localdir</varname>, <varname>rsh</varname> and <varname>scmdata</varname>. The <varname>module</varname> specifies which module to check out, the <varname>tag</varname> describes which CVS TAG should be used for the checkout. By default the TAG is empty. A <varname>date</varname> 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.<varname>method</varname> is by default <emphasis>pserver</emphasis>. If <emphasis>ext</emphasis> is used the <varname>rsh</varname> parameter will be evaluated and <varname>CVS_RSH</varname> will be set. Finally, <varname>localdir</varname> is used to checkout into a special directory relative to <varname>CVSDIR</varname>.
321
322<screen><varname>SRC_URI</varname> = "cvs://CVSROOT;module=mymodule;tag=some-version;method=ext" 322<screen><varname>SRC_URI</varname> = "cvs://CVSROOT;module=mymodule;tag=some-version;method=ext"
323<varname>SRC_URI</varname> = "cvs://CVSROOT;module=mymodule;date=20060126;localdir=usethat" 323<varname>SRC_URI</varname> = "cvs://CVSROOT;module=mymodule;date=20060126;localdir=usethat"
324</screen> 324</screen>
@@ -326,11 +326,10 @@ a per URI parameters separated by a <quote>;</quote> consisting of a key and a v
326 </section> 326 </section>
327 327
328 <section> 328 <section>
329 <title>HTTP/FTP Fetcher</title> 329 <title>HTTP/FTP fetcher</title>
330 <para>The URNs for the HTTP/FTP are <emphasis>http</emphasis>, <emphasis>https</emphasis> and <emphasis>ftp</emphasis>. This Fetcher honors the variables <varname>DL_DIR</varname>, <varname>FETCHCOMMAND_wget</varname>, <varname>PREMIRRORS</varname>, <varname>MIRRORS</varname>. The <varname>DL_DIR</varname> defines where to store the fetched file, <varname>FETCHCOMMAND</varname> contains the command used for fetching. <quote>${URI}</quote> and <quote>${FILES}</quote> will be replaced by the uri and basename of the to be fetched file. <varname>PREMIRRORS</varname> 330 <para>The URNs for the HTTP/FTP fetcher are <emphasis>http</emphasis>, <emphasis>https</emphasis> and <emphasis>ftp</emphasis>. This fetcher honors the variables <varname>DL_DIR</varname>, <varname>FETCHCOMMAND_wget</varname>, <varname>PREMIRRORS</varname>, <varname>MIRRORS</varname>. The <varname>DL_DIR</varname> defines where to store the fetched file. <varname>FETCHCOMMAND</varname> contains the command used for fetching. <quote>${URI}</quote> and <quote>${FILES}</quote> will be replaced by the URI and basename of the file to be fetched. <varname>PREMIRRORS</varname> will be tried first when fetching a file. If that fails, the actual file will be tried and finally all <varname>MIRRORS</varname> will be tried.
331will be tried first when fetching a file if that fails the actual file will be tried and finally all <varname>MIRRORS</varname> will be tried.
332 </para> 331 </para>
333 <para>The only supported Parameter is <varname>md5sum</varname>. After a fetch the <varname>md5sum</varname> of the file will be calculated and the two sums will be compared. 332 <para>The only supported parameter is <varname>md5sum</varname>. After a fetch the <varname>md5sum</varname> of the file will be calculated and the two sums will be compared.
334 </para> 333 </para>
335 <para><screen><varname>SRC_URI</varname> = "http://oe.handhelds.org/not_there.aac;md5sum=12343" 334 <para><screen><varname>SRC_URI</varname> = "http://oe.handhelds.org/not_there.aac;md5sum=12343"
336<varname>SRC_URI</varname> = "ftp://oe.handhelds.org/not_there_as_well.aac;md5sum=1234" 335<varname>SRC_URI</varname> = "ftp://oe.handhelds.org/not_there_as_well.aac;md5sum=1234"
@@ -339,19 +338,19 @@ will be tried first when fetching a file if that fails the actual file will be t
339 </section> 338 </section>
340 339
341 <section> 340 <section>
342 <title>SVK Fetcher</title> 341 <title>SVK fetcher</title>
343 <para> 342 <para>
344 <emphasis>Currently NOT supported</emphasis> 343 <emphasis>Currently NOT supported</emphasis>
345 </para> 344 </para>
346 </section> 345 </section>
347 346
348 <section> 347 <section>
349 <title>SVN Fetcher</title> 348 <title>SVN fetcher</title>
350 <para>The URN for the SVN Fetcher is <emphasis>svn</emphasis>. 349 <para>The URN for the SVN fetcher is <emphasis>svn</emphasis>.
351 </para> 350 </para>
352 <para>This Fetcher honors the variables <varname>FETCHCOMMAND_svn</varname>, <varname>DL_DIR</varname>, <varname>SRCDATE</varname>. <varname>FETCHCOMMAND</varname> contains the subversion command, <varname>DL_DIR</varname> is the directory where tarballs will be saved, <varname>SRCDATE</varname> specifies which date to use when doing the fetching (the special value of "now" will cause the checkout to be updated on every build). 351 <para>This fetcher honors the variables <varname>FETCHCOMMAND_svn</varname>, <varname>DL_DIR</varname>, <varname>SRCDATE</varname>. <varname>FETCHCOMMAND</varname> contains the subversion command. <varname>DL_DIR</varname> is the directory where tarballs will be saved. <varname>SRCDATE</varname> specifies which date to use when doing the fetching (the special value of "now" will cause the checkout to be updated on every build).
353 </para> 352 </para>
354 <para>The supported Parameters are <varname>proto</varname>, <varname>rev</varname> and <varname>scmdata</varname>. <varname>proto</varname> is the subversion protocol, <varname>rev</varname> is the subversion revision. If <varname>scmdata</varname> is set to <quote>keep</quote>, the <quote>.svn</quote> directories will be available during compile-time. 353 <para>The supported parameters are <varname>proto</varname>, <varname>rev</varname> and <varname>scmdata</varname>. <varname>proto</varname> is the Subversion protocol, <varname>rev</varname> is the Subversion revision. If <varname>scmdata</varname> is set to <quote>keep</quote>, the <quote>.svn</quote> directories will be available during compile-time.
355 </para> 354 </para>
356 <para><screen><varname>SRC_URI</varname> = "svn://svn.oe.handhelds.org/svn;module=vip;proto=http;rev=667" 355 <para><screen><varname>SRC_URI</varname> = "svn://svn.oe.handhelds.org/svn;module=vip;proto=http;rev=667"
357<varname>SRC_URI</varname> = "svn://svn.oe.handhelds.org/svn/;module=opie;proto=svn+ssh;date=20060126" 356<varname>SRC_URI</varname> = "svn://svn.oe.handhelds.org/svn/;module=opie;proto=svn+ssh;date=20060126"
@@ -359,12 +358,12 @@ will be tried first when fetching a file if that fails the actual file will be t
359 </section> 358 </section>
360 359
361 <section> 360 <section>
362 <title>GIT Fetcher</title> 361 <title>GIT fetcher</title>
363 <para>The URN for the GIT Fetcher is <emphasis>git</emphasis>. 362 <para>The URN for the GIT Fetcher is <emphasis>git</emphasis>.
364 </para> 363 </para>
365 <para>The Variables <varname>DL_DIR</varname>, <varname>GITDIR</varname> are used. <varname>DL_DIR</varname> will be used to store the checkedout version. <varname>GITDIR</varname> will be used as the base directory where the git tree is cloned to. 364 <para>The Variables <varname>DL_DIR</varname>, <varname>GITDIR</varname> are used. <varname>DL_DIR</varname> will be used to store the checkedout version. <varname>GITDIR</varname> will be used as the base directory where the git tree is cloned to.
366 </para> 365 </para>
367 <para>The Parameters are <emphasis>tag</emphasis>, <emphasis>protocol</emphasis> and <emphasis>scmdata</emphasis>. <emphasis>tag</emphasis> is a git tag, the default is <quote>master</quote>. <emphasis>protocol</emphasis> is the git protocol to use and defaults to <quote>rsync</quote>. If <emphasis>scmdata</emphasis> is set to <quote>keep</quote>, the <quote>.git</quote> directory will be available during compile-time. 366 <para>The parameters are <emphasis>tag</emphasis>, <emphasis>protocol</emphasis> and <emphasis>scmdata</emphasis>. <emphasis>tag</emphasis> is a Git tag, the default is <quote>master</quote>. <emphasis>protocol</emphasis> is the Git protocol to use and defaults to <quote>rsync</quote>. If <emphasis>scmdata</emphasis> is set to <quote>keep</quote>, the <quote>.git</quote> directory will be available during compile-time.
368 </para> 367 </para>
369 <para><screen><varname>SRC_URI</varname> = "git://git.oe.handhelds.org/git/vip.git;tag=version-1" 368 <para><screen><varname>SRC_URI</varname> = "git://git.oe.handhelds.org/git/vip.git;tag=version-1"
370<varname>SRC_URI</varname> = "git://git.oe.handhelds.org/git/vip.git;protocol=http" 369<varname>SRC_URI</varname> = "git://git.oe.handhelds.org/git/vip.git;protocol=http"
@@ -375,13 +374,13 @@ will be tried first when fetching a file if that fails the actual file will be t
375 374
376 375
377 <chapter> 376 <chapter>
378 <title>The bitbake command</title> 377 <title>The BitBake command</title>
379 <section> 378 <section>
380 <title>Introduction</title> 379 <title>Introduction</title>
381 <para>bitbake is the primary command in the system. It facilitates executing tasks in a single .bb file, or executing a given task on a set of multiple .bb files, accounting for interdependencies amongst them.</para> 380 <para>bitbake is the primary command in the system. It facilitates executing tasks in a single .bb file, or executing a given task on a set of multiple .bb files, accounting for interdependencies amongst them.</para>
382 </section> 381 </section>
383 <section> 382 <section>
384 <title>Usage and Syntax</title> 383 <title>Usage and syntax</title>
385 <para> 384 <para>
386 <screen><prompt>$ </prompt>bitbake --help 385 <screen><prompt>$ </prompt>bitbake --help
387usage: bitbake [options] [package ...] 386usage: bitbake [options] [package ...]
@@ -436,7 +435,7 @@ options:
436 <para> 435 <para>
437 <example> 436 <example>
438 <title>Executing a task against a single .bb</title> 437 <title>Executing a task against a single .bb</title>
439 <para>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 <quote>build</quote> by default). It obeys intertask dependencies when doing so.</para> 438 <para>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 <quote>build</quote> by default). It obeys intertask dependencies when doing so.</para>
440 <para><quote>clean</quote> task:</para> 439 <para><quote>clean</quote> task:</para>
441 <para><screen><prompt>$ </prompt>bitbake -b blah_1.0.bb -c clean</screen></para> 440 <para><screen><prompt>$ </prompt>bitbake -b blah_1.0.bb -c clean</screen></para>
442 <para><quote>build</quote> task:</para> 441 <para><quote>build</quote> task:</para>
@@ -446,8 +445,8 @@ options:
446 <para> 445 <para>
447 <example> 446 <example>
448 <title>Executing tasks against a set of .bb files</title> 447 <title>Executing tasks against a set of .bb files</title>
449 <para>There are a number of additional complexities introduced when one wants to manage 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.</para> 448 <para>There are a number of additional complexities introduced when one wants to manage 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.</para>
450 <para>The next section, Metadata, outlines how one goes about specifying such things.</para> 449 <para>The next section, Metadata, outlines how to specify such things.</para>
451 <para>Note that the bitbake command, when not using --buildfile, accepts a <varname>PROVIDER</varname>, not a filename or anything else. By default, a .bb generally PROVIDES its packagename, packagename-version, and packagename-version-revision.</para> 450 <para>Note that the bitbake command, when not using --buildfile, accepts a <varname>PROVIDER</varname>, not a filename or anything else. By default, a .bb generally PROVIDES its packagename, packagename-version, and packagename-version-revision.</para>
452 <screen><prompt>$ </prompt>bitbake blah</screen> 451 <screen><prompt>$ </prompt>bitbake blah</screen>
453 <screen><prompt>$ </prompt>bitbake blah-1.0</screen> 452 <screen><prompt>$ </prompt>bitbake blah-1.0</screen>
@@ -459,8 +458,8 @@ options:
459 <example> 458 <example>
460 <title>Generating dependency graphs</title> 459 <title>Generating dependency graphs</title>
461 <para>BitBake is able to generate dependency graphs using the dot syntax. These graphs can be converted 460 <para>BitBake is able to generate dependency graphs using the dot syntax. These graphs can be converted
462to images using the <application>dot</application> application from <ulink url="http://www.graphviz.org">graphviz</ulink>. 461to images using the <application>dot</application> application from <ulink url="http://www.graphviz.org">Graphviz</ulink>.
463Two files will be written into the current working directory, <emphasis>depends.dot</emphasis> containing dependency information at the package level and <emphasis>task-depends.dot</emphasis> containing a breakdown of the dependencies at the task level. To stop depending on common depends one can use the <prompt>-I depend</prompt> to omit these from the graph. This can lead to more readable graphs. E.g. this way <varname>DEPENDS</varname> from inherited classes, e.g. base.bbclass, can be removed from the graph.</para> 462Two files will be written into the current working directory, <emphasis>depends.dot</emphasis> containing dependency information at the package level and <emphasis>task-depends.dot</emphasis> containing a breakdown of the dependencies at the task level. To stop depending on common depends, one can use the <prompt>-I depend</prompt> to omit these from the graph. This can lead to more readable graphs. This way, <varname>DEPENDS</varname> from inherited classes such as base.bbclass can be removed from the graph.</para>
464 <screen><prompt>$ </prompt>bitbake -g blah</screen> 463 <screen><prompt>$ </prompt>bitbake -g blah</screen>
465 <screen><prompt>$ </prompt>bitbake -g -I virtual/whatever -I bloom blah</screen> 464 <screen><prompt>$ </prompt>bitbake -g -I virtual/whatever -I bloom blah</screen>
466 </example> 465 </example>
@@ -468,20 +467,20 @@ Two files will be written into the current working directory, <emphasis>depends.
468 </section> 467 </section>
469 <section> 468 <section>
470 <title>Special variables</title> 469 <title>Special variables</title>
471 <para>Certain variables affect bitbake operation:</para> 470 <para>Certain variables affect BitBake operation:</para>
472 <section> 471 <section>
473 <title><varname>BB_NUMBER_THREADS</varname></title> 472 <title><varname>BB_NUMBER_THREADS</varname></title>
474 <para> The number of threads bitbake should run at once (default: 1).</para> 473 <para> The number of threads BitBake should run at once (default: 1).</para>
475 </section> 474 </section>
476 </section> 475 </section>
477 <section> 476 <section>
478 <title>Metadata</title> 477 <title>Metadata</title>
479 <para>As you may have seen in the usage information, or in the information about .bb files, the BBFILES variable is how the bitbake tool locates its files. This variable is a space separated list of files that are available, and supports wildcards. 478 <para>As you may have seen in the usage information, or in the information about .bb files, the <varname>BBFILES</varname> variable is how the BitBake tool locates its files. This variable is a space separated list of files that are available, and supports wildcards.
480 <example> 479 <example>
481 <title>Setting BBFILES</title> 480 <title>Setting BBFILES</title>
482 <programlisting><varname>BBFILES</varname> = "/path/to/bbfiles/*.bb"</programlisting> 481 <programlisting><varname>BBFILES</varname> = "/path/to/bbfiles/*.bb"</programlisting>
483 </example></para> 482 </example></para>
484 <para>With regard to dependencies, it expects the .bb to define a <varname>DEPENDS</varname> variable, which contains a space separated list of <quote>package names</quote>, which themselves are the <varname>PN</varname> variable. The <varname>PN</varname> variable is, in general, by default, set to a component of the .bb filename.</para> 483 <para>With regard to dependencies, it expects the .bb to define a <varname>DEPENDS</varname> variable, which contains a space separated list of <quote>package names</quote>, which themselves are the <varname>PN</varname> variable. The <varname>PN</varname> variable is, in general, set to a component of the .bb filename by default.</para>
485 <example> 484 <example>
486 <title>Depending on another .bb</title> 485 <title>Depending on another .bb</title>
487 <para>a.bb: 486 <para>a.bb:
@@ -494,7 +493,7 @@ DEPENDS += "package-b"</screen>
494 </example> 493 </example>
495 <example> 494 <example>
496 <title>Using PROVIDES</title> 495 <title>Using PROVIDES</title>
497 <para>This example shows the usage of the PROVIDES variable, which allows a given .bb to specify what functionality it provides.</para> 496 <para>This example shows the usage of the <varname>PROVIDES</varname> variable, which allows a given .bb to specify what functionality it provides.</para>
498 <para>package1.bb: 497 <para>package1.bb:
499 <screen>PROVIDES += "virtual/package"</screen> 498 <screen>PROVIDES += "virtual/package"</screen>
500 </para> 499 </para>
@@ -504,16 +503,16 @@ DEPENDS += "package-b"</screen>
504 <para>package3.bb: 503 <para>package3.bb:
505 <screen>PROVIDES += "virtual/package"</screen> 504 <screen>PROVIDES += "virtual/package"</screen>
506 </para> 505 </para>
507 <para>As you can see, here there are two different .bb's that provide the same functionality (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.</para> 506 <para>As you can see, we have two different .bb's that provide the same functionality (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.</para>
508 <para>The following would go into a .conf file, to select package1: 507 <para>The following would go into a .conf file, to select package1:
509 <screen>PREFERRED_PROVIDER_virtual/package = "package1"</screen> 508 <screen>PREFERRED_PROVIDER_virtual/package = "package1"</screen>
510 </para> 509 </para>
511 </example> 510 </example>
512 <example> 511 <example>
513 <title>Specifying version preference</title> 512 <title>Specifying version preference</title>
514 <para>When there are multiple <quote>versions</quote> of a given package, bitbake defaults to selecting the most recent version, unless otherwise specified. If the .bb in question has a <varname>DEFAULT_PREFERENCE</varname> 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 preferences for the default selected version. In addition, the user can specify their preferences with regard to version.</para> 513 <para>When there are multiple <quote>versions</quote> of a given package, BitBake defaults to selecting the most recent version, unless otherwise specified. If the .bb in question has a <varname>DEFAULT_PREFERENCE</varname> 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.</para>
515 <para>If the first .bb is named <filename>a_1.1.bb</filename>, then the <varname>PN</varname> variable will be set to <quote>a</quote>, and the <varname>PV</varname> variable will be set to 1.1.</para> 514 <para>If the first .bb is named <filename>a_1.1.bb</filename>, then the <varname>PN</varname> variable will be set to <quote>a</quote>, and the <varname>PV</varname> variable will be set to 1.1.</para>
516 <para>If we then have an <filename>a_1.2.bb</filename>, bitbake will choose 1.2 by default. However, if we define the following variable in a .conf that bitbake parses, we can change that. 515 <para>If we then have an <filename>a_1.2.bb</filename>, BitBake will choose 1.2 by default. However, if we define the following variable in a .conf that BitBake parses, we can change that.
517 <screen>PREFERRED_VERSION_a = "1.1"</screen> 516 <screen>PREFERRED_VERSION_a = "1.1"</screen>
518 </para> 517 </para>
519 </example> 518 </example>