Usage and documentation by Felix Fietkau, based on uClibc Buildroot
+
Usage and documentation by Felix Fietkau and Waldemar Brodkorb, based on uClibc Buildroot
documentation by Thomas Petazzoni. Contributions from Karsten Kruse,
- Ned Ludd, Martin Herren.
+ Ned Ludd, Martin Herren. OpenWrt Kernel Module Creation Howto by Markus Becker.
@@ -80,17 +88,25 @@
gcc, binutils, uClibc and all the tools by hand.
Of course, doing so is possible. But dealing with all configure options,
with all problems of every gcc or binutils
- version it very time-consuming and uninteresting. OpenWrt Buildroot automates this
+ version is very time-consuming and uninteresting. OpenWrt Buildroot automates this
process through the use of Makefiles, and has a collection of patches for
each gcc and binutils version to make them work
- on the MIPS architecture of most Broadcom based Wireless Routers.
+ on the MIPS architecture of most Wireless Routers.
Obtaining OpenWrt Buildroot
-
OpenWrt Buildroot is currently available as experimental snapshots
OpenWrt Buildroot is available via SVN aka subversion.
+ For any kind of OpenWrt development you should get the latest version from svn via:
+
+ $ svn co https://svn.openwrt.org/openwrt/trunk/
+
+
If you only like to create your own custom firmware images and packages we
+ strongly suggest to use the SVN branch of the stable version (whiterussian):
+
+
+ $ svn co https://svn.openwrt.org/openwrt/branches/whiterussian/
+
+
Using OpenWrt Buildroot
@@ -128,8 +144,8 @@
squashfs
jffs2 contains a writable root filesystem, which will expand to
- the size of your flash image. Note that you if you use the generic firmware
- Image, you need to pick the right image for your Flash size, because of different
+ the size of your flash image. Note: if you use the generic firmware image, you
+ need to pick the right image for your flash size, because of different
eraseblock sizes.
squashfs contains a read-only root filesystem using a modified
@@ -152,7 +168,7 @@
tools or packages, these changes will be lost.
Customize the target filesystem skeleton, available under
- target/default/target_skeleton/. You can customize
+ package/base-files/default/. You can customize
configuration files or other stuff here. However, the full file hierarchy
is not yet present, because it's created during the compilation process.
So you can't do everything on this target filesystem skeleton, but
@@ -196,7 +212,7 @@
configuration, and the latter is used if you have selected
locale support.
-
Run the compilation again
+
Run the compilation again.
@@ -231,11 +247,13 @@
target (in the target directory) contains the
Makefiles and associated files for software related to the generation of
- the target root filesystem image. Four types of filesystems are supported
+ the target root filesystem image and the linux kernel for the different
+ system on a chip boards, used in the Wireless Routers.
+ Two types of filesystems are supported
: jffs2 and squashfs.
-
Each directory contains at least 3 files :
+
Each directory contains at least 2 files :
Makefile is the Makefile that downloads, configures,
@@ -264,20 +282,20 @@
is your architecture). This is where the cross compilation toolchain will
be compiled.
-
Setup the staging directory (build_ARCH/staging_dir/ by
+
Setup the staging directory (staging_dir_ARCH/ by
default). This is where the cross-compilation toolchain will be
installed. If you want to use the same cross-compilation toolchain for
other purposes, such as compiling third-party applications, you can add
- build_ARCH/staging_dir/bin to your PATH, and then use
+ staging_dir_ARCH/bin to your PATH, and then use
arch-linux-gcc to compile your application. In order to
setup this staging directory, it first removes it, and then it creates
various subdirectories and symlinks inside it.
Create the target directory (build_ARCH/root/ by
default) and the target filesystem skeleton. This directory will contain
- the final root filesystem. To setup it up, it first deletes it, then it
+ the final root filesystem. To set it up, it first deletes it, then it
copies the skeleton available in target/default/target_skeleton
- and then removes useless CVS/ directories.
+ and then removes useless SVN/ directories.
Call the prepare, compile and install
targets for the subdirectories toolchain, package
@@ -292,25 +310,25 @@
use the toolchain that was generated by the Buildroot.
The toolchain generated by the Buildroot by default is located in
- build_ARCH/staging_dir/. The simplest way to use it
- is to add build_ARCH/staging_dir/bin/ to your PATH
- environnement variable, and then to use
+ staging_dir_ARCH. The simplest way to use it
+ is to add staging_dir_ARCH/bin/ to your PATH
+ environment variable, and then to use
arch-linux-gcc, arch-linux-objdump,
arch-linux-ld, etc.
For example, you may add the following to your
.bashrc (considering you're building for the MIPS
architecture and that Buildroot is located in
- ~/buildroot/) :
Important : do not try to move the toolchain to an other
@@ -324,9 +342,9 @@ mips-linux-gcc -o foo foo.c
uClibc toolchain outside of buildroot
By default, the cross-compilation toolchain is generated inside
- build_ARCH/staging_dir/. But sometimes, it may be useful to
+ staging_dir_ARCH/. But sometimes, it may be useful to
install it somewhere else, so that it can be used to compile other programs
- or by other users. Moving the build_ARCH/staging_dir/
+ or by other users. Moving the staging_dir_ARCH/
directory elsewhere is not possible, because they are some hardcoded
paths in the toolchain configuration.
@@ -334,7 +352,7 @@ mips-linux-gcc -o foo foo.c
you can configure Buildroot to generate it elsewhere using the
option of the configuration tool : Build options ->
Toolchain and header file location, which defaults to
- $(BUILD_DIR)/staging_dir/.
+ staging_dir_ARCH/.
Location of downloaded packages
@@ -343,7 +361,7 @@ mips-linux-gcc -o foo foo.c
downloaded by the Makefiles are all stored in the
DL_DIR which by default is the dl
directory. It's useful for example if you want to keep a complete
- version of Buildroot which is know to be working with the
+ version of Buildroot which is known to be working with the
associated tarballs. This will allow you to regenerate the
toolchain and the target filesystem with exactly the same
versions.
@@ -368,15 +386,39 @@ mips-linux-gcc -o foo foo.c
config BR2_PACKAGE_FOO
- tristate "foo"
- default n
+ tristate "foo - some nice tool"
+ default m if CONFIG_DEVEL
help
This is a comment that explains what foo is.
+
If you depend on other software or library inside the Buildroot, it
+ is important that you automatically select these packages in your
+ Config.in. Example if foo depends on bar library:
+
+
+config BR2_PACKAGE_FOO
+ tristate "foo - some nice tool"
+ default m if CONFIG_DEVEL
+ select BR2_PACKAGE_LIBBAR
+ help
+ This is a comment that explains what foo is.
+
+
Of course, you can add other options to configure particular
things in your software.
+
Config.in in the package directory
+
+
To add your package to the configuration tool, you need
+ to add the following line to package/Config.in,
+ please add it to a section, which fits the purpose of foo:
+
+
You can skip the usual Version: and Architecture
fields, as they will be generated by the make-ipkg-dir.sh script
- called from your Makefile
+ called from your Makefile. The Depends field is important, so that ipkg will
+ automatically fetch all dependend software on your target system.
The real Makefile
Finally, here's the hardest part. Create a file named
Makefile. It will contain the Makefile rules that
are in charge of downloading, configuring, compiling and installing
- the software. Below is an example that we will comment
- afterwards.
+ the software. Below is an example that we will comment afterwards.
First of all, this Makefile example works for a single
binary software. For other software such as libraries or more
complex stuff with multiple binaries, it should be adapted. Look at
- the other Makefile files in the package
+ the other Makefile files in the package/
directory.
-
At lines 4-11, a couple of useful variables are defined :
+
At lines 5-15, a couple of useful variables are defined:
PKG_NAME : The package name, e.g. foo.
@@ -494,43 +539,42 @@ foo-compile: bar-compile
should be downloaded.
PKG_RELEASE : The release number that will be
- appended to the version number of your ipkg package.
+ appended to the version number of your ipkg package.
+
+
PKG_MD5SUM : The md5sum of the software archive.
+
+
PKG_SOURCE_URL : Space separated list of the HTTP
+ or FTP sites from which the archive is downloaded. It must include the complete
+ path to the directory where FOO_SOURCE can be
+ found.
PKG_SOURCE : The name of the tarball of
your package on the download website of FTP site. As you can see
PKG_NAME and PKG_VERSION are used.
-
PKG_SITE : The HTTP or FTP site from which
- the archive is downloaded. It must include the complete
- path to the directory where FOO_SOURCE can be
- found.
+
PKG_CAT : The tool needed for extraction of the
+ software archive.
-
PKG_DIR : The directory into which the software
+
PKG_BUILD_DIR : The directory into which the software
will be configured and compiled. Basically, it's a subdirectory
- of BUILD_DIR which is created upon decompression of
+ of BUILD_DIR which is created upon extraction of
the tarball.
-
PKG_IPK : The resulting ipkg pacakge
+
PKG_INSTALL_DIR : The directory into the software
+ will be installed. It is a subdirectory of PKG_BUILD_DIR.
-
Lines 13-14 defines a target that downloads the tarball from
- the remote site to the download directory
- (DL_DIR).
-
-
Lines 16-18 defines a target and associated rules that
- uncompress the downloaded tarball. As you can see, this target
- depends on the tarball file, so that the previous target (line
- 13-14) is called before executing the rules of the current
- target. Uncompressing is followed by touching a hidden file
- to mark the software has having been uncompressed. This trick is
- used everywhere in Buildroot Makefile to split steps
- (download, uncompress, configure, compile, install) while still
- having correct dependencies.
-
-
Lines 20-31 defines a target and associated rules that
+
In Line 3 and 17 we include common variables and routines to simplify
+ the process of ipkg creation. It includes routines to download, verify
+ and extract the software package archives.
+
+
Line 19 contains the magic line which automatically creates the
+ ipkg for us.
+
+
Lines 21-33 defines a target and associated rules that
configures the software. It depends on the previous target (the
- hidden .source file) so that we are sure the software has
+ hidden .prepared file) so that we are sure the software has
been uncompressed. In order to configure it, it basically runs the
well-known ./configurescript. As we may be doing
cross-compilation, target, host and
@@ -540,41 +584,21 @@ foo-compile: bar-compile
filesystem. Finally it creates a .configured file to
mark the software as configured.
-
Lines 33-34 defines a target and a rule that compiles the
+
Lines 35-42 defines a target and a rule that compiles the
software. This target will create the binary file in the
compilation directory, and depends on the software being already
configured (hence the reference to the .configured
- file). It basically runs make inside the source
- directory.
-
-
Lines 36-40 defines a target and associated rules that create
- the ipkg package which can optionally be embedded into
- the resulting firmware image. It depends on the binary file in
- the source directory, to make sure the software has been compiled.
- It uses the make-ipkg-dir.sh script, which will create the ipkg
- build directory for your package, copy your control file into
- that directory and add version and architecture information.
- Then it calls the install target of the
- software Makefile by passing a prefix
- argument, so that the Makefile doesn't try to install
- the software inside host /usr but inside target
- /usr. After the installation, the
- /usr/man directory inside the target filesystem is
- removed to save space.
+ file). Afterwards it installs the resulting binary into the
+ PKG_INSTALL_DIR. It basically runs
+ make install inside the source directory.
+
+
Lines 44-50 defines a target and associated rules that create
+ the ipkg package, which can optionally be embedded into
+ the resulting firmware image. It manually installs all files you
+ want to integrate in your resulting ipkg. RSTRIP will
+ recursevily strip all binaries and libraries.
Finally IPKG_BUILD is called to create the package.
-
Line 42 and 43 define the installation target of your package,
- which will embed the software into the target filesystem.
-
-
Lines 45-50 define the main targets that the Makefile in the
- package dir calls.
-
-
prepare : Download and unpack the source
-
compile : Compile the source and create the package
-
install : Embed the package into the target filesystem
-
clean : Remove all the files created by the build process
-
-
Conclusion
As you can see, adding a software to buildroot is simply a
@@ -583,13 +607,104 @@ foo-compile: bar-compile
the software.
If you package software that might be useful for other persons,
- don't forget to send a patch to OpenWrt developers !
+ don't forget to send a patch to OpenWrt developers!
+ Use the mail address: openwrt-devel@openwrt.org
+
Resources
-
To learn more about OpenWrt Buildroot you can visit this
- website: http://openwrt.org/
+
To learn more about OpenWrt you can visit this website:
+ http://openwrt.org/
+
+
+
+
+
+
OpenWrt Kernel Module Creation Howto
+
+
+
About OpenWrt Kernel Module Compilation
+
+
You are planning to compile a kernel module? This howto will
+explain what you have to do, to have your kernel module installable as
+an ipkg.
+
+
Enable the kernel options
+
+
Enable the kernel options you want by modifying
+build_mipsel/linux/.config. We are assuming, that you already had your
+kernel compiled once here. You can do the modification by hand or by
+
+
+$ cd build_mipsel/linux
+$ make menuconfig
+
+
+And copy it, so your changes are not getting lost, when doing a 'make
+dirclean'. Here we assume that you are compiling for Broadcom chipset
+based devices:
+
+
+
+Where CONFIG_USB_KEYB is the kernel option, USB_KEYBOARD is the last
+part of BR2_PACKAGE_KMOD_USB_KEYBOARD and usb-kbd is part of the
+filename of the created ipkg.
+
+
Specify the ipkg control file
+
+
Create e.g. target/linux/control/kmod-usb-kbd.control with content similar to this:
+
+
+Package: kmod-usb-kbd
+Priority: optional
+Section: sys
+Maintainer: Markus Becker <mab@comnets.uni-bremen.de>
+Source: buildroot internal
+Description: Kernel Support for USB Keyboards
+