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15 <h1>OpenWrt Buildroot</h1>
16 </div>
17
18 <p>Usage and documentation by Felix Fietkau and Waldemar Brodkorb, based on uClibc Buildroot
19 documentation by Thomas Petazzoni. Contributions from Karsten Kruse,
20 Ned Ludd, Martin Herren. OpenWrt Kernel Module Creation Howto by Markus Becker.</p>
21
22 <p><small>Last modification : $Id$</small></p>
23
24 <ul>
25 <li><a href="#about">About OpenWrt Buildroot</a></li>
26 <li><a href="#download">Obtaining OpenWrt Buildroot</a></li>
27 <li><a href="#using">Using OpenWrt Buildroot</a></li>
28 <li><a href="#custom_targetfs">Customizing the target filesystem</a></li>
29 <li><a href="#custom_busybox">Customizing the Busybox
30 configuration</a></li>
31 <li><a href="#custom_uclibc">Customizing the uClibc
32 configuration</a></li>
33 <li><a href="#buildroot_innards">How OpenWrt Buildroot works</a></li>
34 <li><a href="#using_toolchain">Using the uClibc toolchain</a></li>
35 <li><a href="#toolchain_standalone">Using the uClibc toolchain
36 outside of Buildroot</a></li>
37 <li><a href="#downloaded_packages">Location of downloaded packages</a></li>
38 <li><a href="#add_software">Extending OpenWrt with more Software</a></li>
39 <li><a href="#links">Ressources</a></li>
40 <br>
41 <li><a href="#about_module">About OpenWrt Kernel Module Compilation</a></li>
42 <li><a href="#kernel">Enable the kernel options</a></li>
43 <li><a href="#buildroot_option">Create a buildroot option</a></li>
44 <li><a href="#binary">Define the binary files for the kernel module</a></li>
45 <li><a href="#control">Specify the ipkg control file</a></li>
46 <li><a href="#compile">Compile the kernel module</a></li>
47
48 </ul>
49
50 <h2><a name="about" id="about"></a>About OpenWrt Buildroot</h2>
51
52 <p>OpenWrt Buildroot is a set of Makefiles and patches that allows to easily
53 generate both a cross-compilation toolchain and a root filesystem for your
54 Wireless Router. The cross-compilation toolchain uses uClibc (<a href=
55 "http://www.uclibc.org/">http://www.uclibc.org/</a>), a tiny C standard
56 library.</p>
57
58 <p>A compilation toolchain is the set of tools that allows to
59 compile code for your system. It consists of a compiler (in our
60 case, <code>gcc</code>), binary utils like assembler and linker
61 (in our case, <code>binutils</code>) and a C standard library (for
62 example <a href="http://www.gnu.org/software/libc/libc.html">GNU
63 Libc</a>, <a href="http://www.uclibc.org">uClibc</a> or <a
64 href="http://www.fefe.de/dietlibc/">dietlibc</a>). The system
65 installed on your development station certainly already has a
66 compilation toolchain that you can use to compile application that
67 runs on your system. If you're using a PC, your compilation
68 toolchain runs on an x86 processor and generates code for a x86
69 processor. Under most Linux systems, the compilation toolchain
70 uses the GNU libc as C standard library. This compilation
71 toolchain is called the "host compilation toolchain", and more
72 generally, the machine on which it is running, and on which you're
73 working is called the "host system". The compilation toolchain is
74 provided by your distribution, and OpenWrt Buildroot has nothing to do
75 with it.</p>
76
77 <p>As said above, the compilation toolchain that comes with your system
78 runs and generates code for the processor of your host system. As your
79 embedded system has a different processor, you need a cross-compilation
80 toolchain: it's a compilation toolchain that runs on your host system but
81 that generates code for your target system (and target processor). For
82 example, if your host system uses x86 and your target system uses MIPS, the
83 regular compilation toolchain of your host runs on x86 and generates code
84 for x86, while the cross-compilation toolchain runs on x86 and generates
85 code for MIPS.</p>
86
87 <p>You might wonder why such a tool is needed when you can compile
88 <code>gcc</code>, <code>binutils</code>, uClibc and all the tools by hand.
89 Of course, doing so is possible. But dealing with all configure options,
90 with all problems of every <code>gcc</code> or <code>binutils</code>
91 version is very time-consuming and uninteresting. OpenWrt Buildroot automates this
92 process through the use of Makefiles, and has a collection of patches for
93 each <code>gcc</code> and <code>binutils</code> version to make them work
94 on the MIPS architecture of most Wireless Routers.</p>
95
96 <h2><a name="download" id="download"></a>Obtaining OpenWrt Buildroot</h2>
97
98 <p>OpenWrt Buildroot is available via SVN aka subversion.
99 For any kind of OpenWrt development you should get the latest version from svn via:</p>
100 <pre>
101 $ svn co https://svn.openwrt.org/openwrt/trunk/
102 </pre>
103 <p>If you only like to create your own custom firmware images and packages we
104 strongly suggest to use the SVN branch of the stable version (whiterussian):
105 </p>
106 <pre>
107 $ svn co https://svn.openwrt.org/openwrt/branches/whiterussian/
108 </pre>
109
110
111 <h2><a name="using" id="using"></a>Using OpenWrt Buildroot</h2>
112
113 <p>OpenWrt Buildroot has a nice configuration tool similar to the one you can find
114 in the Linux Kernel (<a href="http://www.kernel.org/">http://www.kernel.org/</a>)
115 or in Busybox (<a href="http://www.busybox.org/">http://www.busybox.org/</a>).
116 Note that you can run everything as a normal user. There is no need to be root to
117 configure and use the Buildroot. The first step is to run the configuration
118 assistant:</p>
119
120 <pre>
121 $ make menuconfig
122 </pre>
123
124 <p>For each entry of the configuration tool, you can find associated help
125 that describes the purpose of the entry.</p>
126
127 <p>Once everything is configured, the configuration tool has generated a
128 <code>.config</code> file that contains the description of your
129 configuration. It will be used by the Makefiles to do what's needed.</p>
130
131 <p>Let's go:</p>
132
133 <pre>
134 $ make
135 </pre>
136
137 <p>This command will download, configure and compile all the selected
138 tools, and finally generate target firmware images and additional packages
139 (depending on your selections in <code>make menuconfig</code>.
140 All the target files can be found in the <code>bin/</code> subdirectory.
141 You can compile firmware images containing two different filesystem types:
142 <ul>
143 <li>jffs2</li>
144 <li>squashfs</li>
145 </ul>
146 <p><code>jffs2</code> contains a writable root filesystem, which will expand to
147 the size of your flash image. Note: if you use the generic firmware image, you
148 need to pick the right image for your flash size, because of different
149 eraseblock sizes.</p>
150
151 <p><code>squashfs</code> contains a read-only root filesystem using a modified
152 <code>squashfs</code> filesystem with LZMA compression. When booting it, you can
153 create a writable second filesystem, which will contain your modifications to
154 the root filesystem, including the packages you install.
155
156 <h2><a name="custom_targetfs" id="custom_targetfs"></a>Customizing the
157 target filesystem</h2>
158
159 <p>There are two ways to customize the resulting target filesystem:</p>
160
161 <ul>
162 <li>Customize the target filesystem directly, and rebuild the image. The
163 target filesystem is available under <code>build_ARCH/root/</code> where
164 <code>ARCH</code> is the chosen target architecture, usually mipsel.
165 You can simply make your changes here, and run make target_install afterwards,
166 which will rebuild the target filesystem image. This method allows to do
167 everything on the target filesystem, but if you decide to rebuild your toolchain,
168 tools or packages, these changes will be lost.</li>
169
170 <li>Customize the target filesystem skeleton, available under
171 <code>package/base-files/default/</code>. You can customize
172 configuration files or other stuff here. However, the full file hierarchy
173 is not yet present, because it's created during the compilation process.
174 So you can't do everything on this target filesystem skeleton, but
175 changes to it remains even when you completely rebuild the cross-compilation
176 toolchain and the tools.<br />
177 </ul>
178
179 <h2><a name="custom_busybox" id="custom_busybox"></a>Customizing the
180 Busybox configuration</h2>
181
182 <p>Busybox is very configurable, and you may want to customize it.
183 Its configuration is completely integrated into the main menuconfig system.
184 You can find it under "OpenWrt Package Selection" =&gt; "Busybox Configuration"</p>
185
186 <h2><a name="custom_uclibc" id="custom_uclibc"></a>Customizing the uClibc
187 configuration</h2>
188
189 <p>Just like <a href="#custom_busybox">BusyBox</a>, <a
190 href="http://www.uclibc.org">uClibc</a> offers a lot of
191 configuration options. They allow to select various
192 functionalities, depending on your needs and limitations.</p>
193
194 <p>The easiest way to modify the configuration of uClibc is to
195 follow these steps :</p>
196
197 <ol>
198
199 <li>Make a first compilation of buildroot without trying to
200 customize uClibc.</li>
201
202 <li>Go into the directory
203 <code>toolchain_build_ARCH/uClibc/</code> and run <code>make
204 menuconfig</code>. The nice configuration assistant, similar to
205 the one used in the Linux Kernel appears. Make
206 your configuration as appropriate.</li>
207
208 <li>Copy the <code>.config</code> file to
209 <code>toolchain/uClibc/uClibc.config</code> or
210 <code>toolchain/uClibc/uClibc.config-locale</code>. The former
211 is used if you haven't selected locale support in the Buildroot
212 configuration, and the latter is used if you have selected
213 locale support.</li>
214
215 <li>Run the compilation again.</li>
216
217 </ol>
218
219 <p>Otherwise, you can simply change
220 <code>toolchain/uClibc/uClibc.config</code> or
221 <code>toolchain/uClibc/uClibc.config-locale</code> without running
222 the configuration assistant.</p>
223
224 <h2><a name="buildroot_innards" id="buildroot_innards"></a>How OpenWrt Buildroot
225 works</h2>
226
227 <p>As said above, OpenWrt is basically a set of Makefiles that download,
228 configure and compiles software with the correct options. It also includes
229 some patches for various software, mainly the ones involved in the
230 cross-compilation tool chain (<code>gcc</code>, <code>binutils</code> and
231 uClibc).</p>
232
233 <p>There is basically one Makefile per software, and they are named <code>Makefile</code>.
234 Makefiles are split into three sections:</p>
235
236 <ul>
237 <li><b>package</b> (in the <code>package/</code> directory) contains the
238 Makefiles and associated files for all user-space tools that Buildroot
239 can compile and add to the target root filesystem. There is one
240 sub-directory per tool.</li>
241
242 <li><b>toolchain</b> (in the <code>toolchain/</code> directory) contains
243 the Makefiles and associated files for all software related to the
244 cross-compilation toolchain : <code>binutils</code>, <code>ccache</code>,
245 <code>gcc</code>, <code>gdb</code>, <code>kernel-headers</code> and
246 <code>uClibc</code>.</li>
247
248 <li><b>target</b> (in the <code>target</code> directory) contains the
249 Makefiles and associated files for software related to the generation of
250 the target root filesystem image and the linux kernel for the different
251 system on a chip boards, used in the Wireless Routers.
252 Two types of filesystems are supported
253 : jffs2 and squashfs.
254 </ul>
255
256 <p>Each directory contains at least 2 files :</p>
257
258 <ul>
259 <li><code>Makefile</code> is the Makefile that downloads, configures,
260 compiles and installs the software <code>something</code>.</li>
261
262 <li><code>Config.in</code> is a part of the configuration tool
263 description file. It describes the option related to the current
264 software.</li>
265 </ul>
266
267 <p>The main Makefile do the job through the following steps (once the
268 configuration is done):</p>
269
270 <ol>
271 <li>Create the download directory (<code>dl/</code> by default). This is
272 where the tarballs will be downloaded. It is interesting to know that the
273 tarballs are in this directory because it may be useful to save them
274 somewhere to avoid further downloads.</li>
275
276 <li>Create the build directory (<code>build_ARCH/</code> by default,
277 where <code>ARCH</code> is your architecture). This is where all
278 user-space tools while be compiled.</li>
279
280 <li>Create the toolchain build directory
281 (<code>toolchain_build_ARCH/</code> by default, where <code>ARCH</code>
282 is your architecture). This is where the cross compilation toolchain will
283 be compiled.</li>
284
285 <li>Setup the staging directory (<code>staging_dir_ARCH/</code> by
286 default). This is where the cross-compilation toolchain will be
287 installed. If you want to use the same cross-compilation toolchain for
288 other purposes, such as compiling third-party applications, you can add
289 <code>staging_dir_ARCH/bin</code> to your PATH, and then use
290 <code>arch-linux-gcc</code> to compile your application. In order to
291 setup this staging directory, it first removes it, and then it creates
292 various subdirectories and symlinks inside it.</li>
293
294 <li>Create the target directory (<code>build_ARCH/root/</code> by
295 default) and the target filesystem skeleton. This directory will contain
296 the final root filesystem. To set it up, it first deletes it, then it
297 copies the skeleton available in <code>target/default/target_skeleton</code>
298 and then removes useless <code>SVN/</code> directories.</li>
299
300 <li>Call the <code>prepare</code>, <code>compile</code> and <code>install</code>
301 targets for the subdirectories <code>toolchain</code>, <code>package</code>
302 and <code>target</code></li>
303 </ol>
304
305 <h2><a name="using_toolchain" id="using_toolchain"></a>Using the
306 uClibc toolchain</h2>
307
308 <p>You may want to compile your own programs or other software
309 that are not packaged in OpenWrt. In order to do this, you can
310 use the toolchain that was generated by the Buildroot.</p>
311
312 <p>The toolchain generated by the Buildroot by default is located in
313 <code>staging_dir_ARCH</code>. The simplest way to use it
314 is to add <code>staging_dir_ARCH/bin/</code> to your PATH
315 environment variable, and then to use
316 <code>arch-linux-gcc</code>, <code>arch-linux-objdump</code>,
317 <code>arch-linux-ld</code>, etc.</p>
318
319 <p>For example, you may add the following to your
320 <code>.bashrc</code> (considering you're building for the MIPS
321 architecture and that Buildroot is located in
322 <code>~/openwrt/</code>) :</p>
323
324 <pre>
325 export PATH=$PATH:~/openwrt/staging_dir_mipsel/bin/
326 </pre>
327
328 <p>Then you can simply do :</p>
329
330 <pre>
331 mipsel-linux-uclibc-gcc -o foo foo.c
332 </pre>
333
334 <p><b>Important</b> : do not try to move the toolchain to an other
335 directory, it won't work. There are some hard-coded paths in the
336 <i>gcc</i> configuration. If the default toolchain directory
337 doesn't suit your needs, please refer to the <a
338 href="#toolchain_standalone">Using the uClibc toolchain outside of
339 buildroot</a> section.</p>
340
341 <h2><a name="toolchain_standalone" id="toolchain_standalone"></a>Using the
342 uClibc toolchain outside of buildroot</h2>
343
344 <p>By default, the cross-compilation toolchain is generated inside
345 <code>staging_dir_ARCH/</code>. But sometimes, it may be useful to
346 install it somewhere else, so that it can be used to compile other programs
347 or by other users. Moving the <code>staging_dir_ARCH/</code>
348 directory elsewhere is <b>not possible</b>, because they are some hardcoded
349 paths in the toolchain configuration.</p>
350
351 <p>If you want to use the generated toolchain for other purposes,
352 you can configure Buildroot to generate it elsewhere using the
353 option of the configuration tool : <code>Build options -&gt;
354 Toolchain and header file location</code>, which defaults to
355 <code>staging_dir_ARCH/</code>.</p>
356
357 <h2><a name="downloaded_packages"
358 id="downloaded_packages"></a>Location of downloaded packages</h2>
359
360 <p>It might be useful to know that the various tarballs that are
361 downloaded by the <i>Makefiles</i> are all stored in the
362 <code>DL_DIR</code> which by default is the <code>dl</code>
363 directory. It's useful for example if you want to keep a complete
364 version of Buildroot which is known to be working with the
365 associated tarballs. This will allow you to regenerate the
366 toolchain and the target filesystem with exactly the same
367 versions.</p>
368
369 <h2><a name="add_software" id="add_software"></a>Extending OpenWrt with
370 more software</h2>
371
372 <p>This section will only consider the case in which you want to
373 add user-space software.</p>
374
375 <h3>Package directory</h3>
376
377 <p>First of all, create a directory under the <code>package</code>
378 directory for your software, for example <code>foo</code>.</p>
379
380 <h3><code>Config.in</code> file</h3>
381
382 <p>Then, create a file named <code>Config.in</code>. This file
383 will contain the portion of options description related to our
384 <code>foo</code> software that will be used and displayed in the
385 configuration tool. It should basically contain :</p>
386
387 <pre>
388 config BR2_PACKAGE_FOO
389 tristate "foo - some nice tool"
390 default m if CONFIG_DEVEL
391 help
392 This is a comment that explains what foo is.
393 </pre>
394
395 <p>If you depend on other software or library inside the Buildroot, it
396 is important that you automatically select these packages in your
397 <code>Config.in</code>. Example if foo depends on bar library:
398 </p>
399 <pre>
400 config BR2_PACKAGE_FOO
401 tristate "foo - some nice tool"
402 default m if CONFIG_DEVEL
403 select BR2_PACKAGE_LIBBAR
404 help
405 This is a comment that explains what foo is.
406 </pre>
407
408 <p>Of course, you can add other options to configure particular
409 things in your software.</p>
410
411 <h3><code>Config.in</code> in the package directory</h3>
412
413 <p>To add your package to the configuration tool, you need
414 to add the following line to <code>package/Config.in</code>,
415 please add it to a section, which fits the purpose of foo:
416
417 <pre>
418 comment "Networking"
419 source "package/foo/Config.in"
420 </pre>
421
422 <h3><code>Makefile</code> in the package directory</h3>
423
424 <p>To add your package to the build process, you need to edit
425 the Makefile in the <code>package/</code> directory. Locate the
426 lines that look like the following:</p>
427
428 <pre>
429 package-$(BR2_PACKAGE_FOO) += foo
430 </pre>
431
432 <p>As you can see, this short line simply adds the target
433 <code>foo</code> to the list of targets handled by OpenWrt Buildroot.</p>
434
435 <p>In addition to the default dependencies, you make your package
436 depend on another package (e.g. a library) by adding a line:
437
438 <pre>
439 foo-compile: bar-compile
440 </pre>
441
442 <h3>The ipkg control file</h3>
443 <p>Additionally, you need to create a control file which contains
444 information about your package, readable by the <i>ipkg</i> package
445 utility. It should be created as file:
446 <code>package/foo/ipkg/foo.control</code></p>
447
448 <p>The file looks like this</p>
449
450 <pre>
451 1 Package: foo
452 2 Priority: optional
453 3 Section: net
454 4 Maintainer: Foo Software &lt;foo@foosoftware.com&gt;
455 5 Source: http://foosoftware.com
456 6 Depends: libbar
457 7 Description: Package Description
458 </pre>
459
460 <p>You can skip the usual <code>Version:</code> and <code>Architecture</code>
461 fields, as they will be generated by the <code>make-ipkg-dir.sh</code> script
462 called from your Makefile. The Depends field is important, so that ipkg will
463 automatically fetch all dependend software on your target system.</p>
464
465 <h3>The real <i>Makefile</i></h3>
466
467 <p>Finally, here's the hardest part. Create a file named
468 <code>Makefile</code>. It will contain the <i>Makefile</i> rules that
469 are in charge of downloading, configuring, compiling and installing
470 the software. Below is an example that we will comment afterwards.</p>
471
472 <pre>
473 1 # $Id$
474 2
475 3 include $(TOPDIR)/rules.mk
476 4
477 5 PKG_NAME:=foo
478 6 PKG_VERSION:=1.0
479 7 PKG_RELEASE:=1
480 8 PKG_MD5SUM:=4584f226523776a3cdd2fb6f8212ba8d
481 9
482 10 PKG_SOURCE_URL:=http://www.foosoftware.org/downloads
483 11 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
484 12 PKG_CAT:=zcat
485 13
486 14 PKG_BUILD_DIR:=$(BUILD_DIR)/$(PKG_NAME)-$(PKG_VERSION)
487 15 PKG_INSTALL_DIR:=$(PKG_BUILD_DIR)/ipkg-install
488 16
489 17 include $(TOPDIR)/package/rules.mk
490 18
491 19 $(eval $(call PKG_template,FOO,foo,$(PKG_VERSION)-$(PKG_RELEASE),$(ARCH)))
492 20
493 21 $(PKG_BUILD_DIR)/.configured: $(PKG_BUILD_DIR)/.prepared
494 22 (cd $(PKG_BUILD_DIR); \
495 23 $(TARGET_CONFIGURE_OPTS) \
496 24 CFLAGS="$(TARGET_CFLAGS)" \
497 25 ./configure \
498 26 --target=$(GNU_TARGET_NAME) \
499 27 --host=$(GNU_TARGET_NAME) \
500 28 --build=$(GNU_HOST_NAME) \
501 29 --prefix=/usr \
502 30 --sysconfdir=/etc \
503 31 --with-bar="$(STAGING_DIR)/usr" \
504 32 );
505 33 touch $@
506 34
507 35 $(PKG_BUILD_DIR)/.built:
508 36 rm -rf $(PKG_INSTALL_DIR)
509 37 mkdir -p $(PKG_INSTALL_DIR)
510 38 $(MAKE) -C $(PKG_BUILD_DIR) \
511 39 $(TARGET_CONFIGURE_OPTS) \
512 40 install_prefix="$(PKG_INSTALL_DIR)" \
513 41 all install
514 42 touch $@
515 43
516 44 $(IPKG_FOO):
517 46 install -d -m0755 $(IDIR_FOO)/usr/sbin
518 47 cp -fpR $(PKG_INSTALL_DIR)/usr/sbin/foo $(IDIR_FOO)/usr/sbin
519 49 $(RSTRIP) $(IDIR_FOO)
520 50 $(IPKG_BUILD) $(IDIR_FOO) $(PACKAGE_DIR)
521 51
522 52 mostlyclean:
523 53 make -C $(PKG_BUILD_DIR) clean
524 54 rm $(PKG_BUILD_DIR)/.built
525 </pre>
526
527 <p>First of all, this <i>Makefile</i> example works for a single
528 binary software. For other software such as libraries or more
529 complex stuff with multiple binaries, it should be adapted. Look at
530 the other <code>Makefile</code> files in the <code>package/</code>
531 directory.</p>
532
533 <p>At lines 5-15, a couple of useful variables are defined:</p>
534
535 <ul>
536 <li><code>PKG_NAME</code> : The package name, e.g. <i>foo</i>.</li>
537
538 <li><code>PKG_VERSION</code> : The version of the package that
539 should be downloaded.</li>
540
541 <li><code>PKG_RELEASE</code> : The release number that will be
542 appended to the version number of your <i>ipkg</i> package.</li>
543
544 <li><code>PKG_MD5SUM</code> : The md5sum of the software archive.</li>
545
546 <li><code>PKG_SOURCE_URL</code> : Space separated list of the HTTP
547 or FTP sites from which the archive is downloaded. It must include the complete
548 path to the directory where <code>FOO_SOURCE</code> can be
549 found.</li>
550
551 <li><code>PKG_SOURCE</code> : The name of the tarball of
552 your package on the download website of FTP site. As you can see
553 <code>PKG_NAME</code> and <code>PKG_VERSION</code> are used.</li>
554
555 <li><code>PKG_CAT</code> : The tool needed for extraction of the
556 software archive.</li>
557
558 <li><code>PKG_BUILD_DIR</code> : The directory into which the software
559 will be configured and compiled. Basically, it's a subdirectory
560 of <code>BUILD_DIR</code> which is created upon extraction of
561 the tarball.</li>
562
563 <li><code>PKG_INSTALL_DIR</code> : The directory into the software
564 will be installed. It is a subdirectory of <code>PKG_BUILD_DIR</code>.</li>
565
566 </ul>
567
568 <p>In Line 3 and 17 we include common variables and routines to simplify
569 the process of ipkg creation. It includes routines to download, verify
570 and extract the software package archives.</p>
571
572 <p>Line 19 contains the magic line which automatically creates the
573 ipkg for us.</p>
574
575 <p>Lines 21-33 defines a target and associated rules that
576 configures the software. It depends on the previous target (the
577 hidden <code>.prepared</code> file) so that we are sure the software has
578 been uncompressed. In order to configure it, it basically runs the
579 well-known <code>./configure</code>script. As we may be doing
580 cross-compilation, <code>target</code>, <code>host</code> and
581 <code>build</code> arguments are given. The prefix is also set to
582 <code>/usr</code>, not because the software will be installed in
583 <code>/usr</code> on your host system, but in the target
584 filesystem. Finally it creates a <code>.configured</code> file to
585 mark the software as configured.</p>
586
587 <p>Lines 35-42 defines a target and a rule that compiles the
588 software. This target will create the binary file in the
589 compilation directory, and depends on the software being already
590 configured (hence the reference to the <code>.configured</code>
591 file). Afterwards it installs the resulting binary into the
592 <code>PKG_INSTALL_DIR</code>. It basically runs
593 <code>make install</code> inside the source directory.</p>
594
595 <p>Lines 44-50 defines a target and associated rules that create
596 the <i>ipkg</i> package, which can optionally be embedded into
597 the resulting firmware image. It manually installs all files you
598 want to integrate in your resulting ipkg. <code>RSTRIP</code> will
599 recursevily strip all binaries and libraries.
600 Finally <code>IPKG_BUILD</code> is called to create the package.</p>
601
602 <h3>Conclusion</h3>
603
604 <p>As you can see, adding a software to buildroot is simply a
605 matter of writing a <i>Makefile</i> using an already existing
606 example and to modify it according to the compilation process of
607 the software.</p>
608
609 <p>If you package software that might be useful for other persons,
610 don't forget to send a patch to OpenWrt developers!
611 Use the mail address: openwrt-devel@openwrt.org
612 </p>
613
614 <h2><a name="links" id="links"></a>Resources</h2>
615
616 <p>To learn more about OpenWrt you can visit this website:
617 <a href="http://openwrt.org/">http://openwrt.org/</a></p>
618
619 </div>
620
621 <div class="main">
622 <div class="titre">
623 <h1>OpenWrt Kernel Module Creation Howto</h1>
624 </div>
625
626 <h2><a name="about_module" id="about_module"></a>About OpenWrt Kernel Module Compilation</h2>
627
628 <p>You are planning to compile a kernel module? This howto will
629 explain what you have to do, to have your kernel module installable as
630 an ipkg.</p>
631
632 <h2><a name="kernel" id="kernel"></a>Enable the kernel options</h2>
633
634 <p>Enable the kernel options you want by modifying
635 build_mipsel/linux/.config. We are assuming, that you already had your
636 kernel compiled once here. You can do the modification by hand or by
637
638 <pre>
639 $ cd build_mipsel/linux
640 $ make menuconfig
641 </pre>
642
643 And copy it, so your changes are not getting lost, when doing a 'make
644 dirclean'. Here we assume that you are compiling for Broadcom chipset
645 based devices:
646
647 <pre> $ cp .config ../../../target/linux/linux-2.4/config/brcm </pre>
648
649 </p>
650 <h2><a name="buildroot_option" id="buildroot_option"></a>Create a buildroot option</h2>
651
652 <p>Create a buildroot option by modifying/inserting into
653 target/linux/Config.in, e.g.
654
655 <pre>
656 config BR2_PACKAGE_KMOD_USB_KEYBOARD
657 tristate "Support for USB keyboards"
658 default m
659 depends BR2_PACKAGE_KMOD_USB_CONTROLLER
660 </pre>
661 </p>
662
663 <h2><a name="binary" id="binary"></a>Define the binary files for the kernel module</h2>
664
665 <p>Define the binary files for the kernel module by modifying/inserting into
666 target/linux/linux-2.4/Makefile, e.g.
667
668 <pre>
669 $(eval $(call KMOD_template,USB_KEYBOARD,usb-kbd,\
670 $(MODULES_DIR)/kernel/drivers/input/input.o \
671 $(MODULES_DIR)/kernel/drivers/input/keybdev.o \
672 $(MODULES_DIR)/kernel/drivers/usb/usbkbd.o \
673 ,CONFIG_USB_KEYB,kmod-usb-core,60,input keybdev usbkbd))
674 </pre>
675
676 Where CONFIG_USB_KEYB is the kernel option, USB_KEYBOARD is the last
677 part of BR2_PACKAGE_KMOD_USB_KEYBOARD and usb-kbd is part of the
678 filename of the created ipkg.</p>
679
680 <h2><a name="control" id="control"></a>Specify the ipkg control file</h2>
681
682 <p>Create e.g. target/linux/control/kmod-usb-kbd.control with content similar to this:
683
684 <pre>
685 Package: kmod-usb-kbd
686 Priority: optional
687 Section: sys
688 Maintainer: Markus Becker &lt;mab@comnets.uni-bremen.de&gt;
689 Source: buildroot internal
690 Description: Kernel Support for USB Keyboards
691 </pre>
692 </p>
693
694 <h2><a name="compile" id="compile"></a>Compile the kernel module</h2>
695
696 <p>Enable the kernel module with
697 <pre>
698 $ make menuconfig
699 </pre>
700 in TOPDIR and selecting it.<br>
701
702 Compile with
703 <pre>
704 $ make dirclean && make
705 </pre>
706 </p>
707 </div>
708
709 </body>
710 </html>