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-rw-r--r--bitbake/doc/user-manual/user-manual-intro.xml55
1 files changed, 55 insertions, 0 deletions
diff --git a/bitbake/doc/user-manual/user-manual-intro.xml b/bitbake/doc/user-manual/user-manual-intro.xml
index 49694fb5c3..05a3fc8989 100644
--- a/bitbake/doc/user-manual/user-manual-intro.xml
+++ b/bitbake/doc/user-manual/user-manual-intro.xml
@@ -228,6 +228,31 @@
228 </para> 228 </para>
229 </section> 229 </section>
230 230
231 <section id='append-bbappend-files'>
232 <title>Append Files</title>
233
234 <para>
235 Append files, which are files that have the
236 <filename>.bbappend</filename> file extension, add or
237 extend build information to an existing
238 recipe file.
239 </para>
240
241 <para>
242 BitBake expects every append file to have a corresponding recipe file.
243 Furthermore, the append file and corresponding recipe file
244 must use the same root filename.
245 The filenames can differ only in the file type suffix used
246 (e.g. <filename>formfactor_0.0.bb</filename> and
247 <filename>formfactor_0.0.bbappend</filename>).
248 </para>
249
250 <para>
251 Information in append files overrides the information in the
252 similarly-named recipe file.
253 </para>
254 </section>
255
231 <section id='configuration-files'> 256 <section id='configuration-files'>
232 <title>Configuration Files</title> 257 <title>Configuration Files</title>
233 258
@@ -269,6 +294,36 @@
269 added during the project development process. 294 added during the project development process.
270 </para> 295 </para>
271 </section> 296 </section>
297
298 <section id='layers'>
299 <title>Layers</title>
300
301 <para>
302 Layers allow you to isolate different types of
303 customizations from each other.
304 While you might find it tempting to keep everything in one layer
305 when working on a single project, the more modular you organize
306 your metadata, the easier it is to cope with future changes.
307 </para>
308
309 <para>
310 To illustrate how you can use layers to keep things modular,
311 consider machine customizations.
312 These types of customizations typically reside in a special layer,
313 rather than a general layer, called a Board Specific Package (BSP) Layer.
314 Furthermore, the machine customizations should be isolated from
315 recipes and metadata that support a new GUI environment, for
316 example.
317 This situation gives you a couple of layers: one for the machine
318 configurations and one for the GUI environment.
319 It is important to understand, however, that the BSP layer can still
320 make machine-specific additions to recipes within
321 the GUI environment layer without polluting the GUI layer itself
322 with those machine-specific changes.
323 You can accomplish this through a recipe that is a BitBake append
324 (<filename>.bbappend</filename>) file.
325 </para>
326 </section>
272 </section> 327 </section>
273 328
274 <section id='obtaining-bitbake'> 329 <section id='obtaining-bitbake'>