So let's take a look at OpenWrt and see how this all works.
-\subsubsection{Download openwrt}
+\subsubsection{Download OpenWrt}
This article refers to the "Kamikaze" branch of OpenWrt, which can be downloaded via
subversion using the following command:
\begin{Verbatim}
-$ svn co https://svn.openwrt.org/openwrt/trunk kamikaze
+$ svn checkout https://svn.openwrt.org/openwrt/trunk kamikaze
\end{Verbatim}
-Additionally, ther is a trac interface on \href{https://dev.openwrt.org/}{https://dev.openwrt.org/}
-which can be used to monitor svn commits and browse the sources.
+Additionally, there is a trac interface on \href{https://dev.openwrt.org/}{https://dev.openwrt.org/}
+which can be used to monitor svn commits and browse the source repository.
\subsubsection{The directory structure}
\texttt{tools} and \texttt{toolchain} refer to common tools which will be
used to build the firmware image, the compiler, and the C library.
-The result of this is three new directories, \texttt{tool\_build}, which is a temporary
-directory for building the target independent tools, \texttt{toolchain\_build\_\textit{<arch>}}
+The result of this is three new directories, \texttt{build\_dir/host}, which is a temporary
+directory for building the target independent tools, \texttt{build\_dir/toolchain-\textit{<arch>}*}
which is used for building the toolchain for a specific architecture, and
-\texttt{staging\_dir\_\textit{<arch>}} where the resulting toolchain is installed.
+\texttt{staging\_dir/toolchain-\textit{<arch>}*} where the resulting toolchain is installed.
You will not need to do anything with the toolchain directory unless you intend to
add a new version of one of the components above.
\begin{itemize}
- \item \texttt{tool\_build}
- \item \texttt{toolchain\_build\_\textit{<arch>}}
+ \item \texttt{build\_dir/host}
+ \item \texttt{build\_dir/toolchain-\textit{<arch>}*}
\end{itemize}
\texttt{package} is for exactly that -- packages. In an OpenWrt firmware, almost everything
is an \texttt{.ipk}, a software package which can be added to the firmware to provide new
features or removed to save space. Note that packages are also maintained outside of the main
-trunk and can be obtained from subversion at the following location:
+trunk and can be obtained from subversion using the package feeds system:
\begin{Verbatim}
-$ svn co https://svn.openwrt.org/openwrt/packages ../packages
+$ ./scripts/feeds update
\end{Verbatim}
Those packages can be used to extend the functionality of the build system and need to be
configuration. From kamikaze you would do something like this:
\begin{Verbatim}
-$ ls
-kamikaze packages
-$ ln -s packages/net/nmap kamikaze/package/nmap
+$ ./scripts/feeds search nmap
+Search results in feed 'packages':
+nmap Network exploration and/or security auditing utility
+
+$ ./scripts/feeds install nmap
\end{Verbatim}
To include all packages, issue the following command:
\begin{Verbatim}
-$ ln -s packages/*/* kamikaze/package/
+$ make package/symlinks
\end{Verbatim}
-
\texttt{target} refers to the embedded platform, this contains items which are specific to
a specific embedded platform. Of particular interest here is the "\texttt{target/linux}"
-directory which is broken down by platform and contains the kernel config and patches
-to the kernel for a particular platform. There's also the "\texttt{target/image}" directory
+directory which is broken down by platform \textit{<arch>} and contains the patches to the
+kernel, profile config, for a particular platform. There's also the "\texttt{target/image}" directory
which describes how to package a firmware for a specific platform.
-Both the target and package steps will use the directory "\texttt{build\_\textit{<arch>}}"
+Both the target and package steps will use the directory "\texttt{build\_
dir/\textit{<arch>}}"
as a temporary directory for compiling. Additionally, anything downloaded by the toolchain,
target or package steps will be placed in the "\texttt{dl}" directory.
\begin{itemize}
- \item \texttt{build\_\textit{<arch>}}
+ \item \texttt{build\_
dir/\textit{<arch>}}
\item \texttt{dl}
\end{itemize}
"\texttt{make V=99}".
During the build process, buildroot will download all sources to the "\texttt{dl}"
-directory and will start patching and compiling them in the "\texttt{build\_\textit{<arch>}}"
+directory and will start patching and compiling them in the "\texttt{build\_
dir/\textit{<arch>}}"
directory. When finished, the resulting firmware will be in the "\texttt{bin}" directory
and packages will be in the "\texttt{bin/packages}" directory.
\begin{itemize}
\item \texttt{package/\textit{<name>}/Makefile}
\item \texttt{package/\textit{<name>}/patches}
- \item \texttt{package/\textit{<name>}/files}
+ \item \texttt{package/\textit{<name>}/files}
\end{itemize}
The patches directory is optional and typically contains bug fixes or optimizations to
Here for example, is \texttt{package/bridge/Makefile}:
\begin{Verbatim}[frame=single,numbers=left]
-#
-# Copyright (C) 2006 OpenWrt.org
-#
-# This is free software, licensed under the GNU General Public License v2.
-# See /LICENSE for more information.
-#
# $Id: Makefile 5624 2006-11-23 00:29:07Z nbd $
include $(TOPDIR)/rules.mk
SECTION:=net
CATEGORY:=Base system
TITLE:=Ethernet bridging configuration utility
- DESCRIPTION:=\
- Manage ethernet bridging: a way to connect networks together to \\\
- form a larger network.
URL:=http://bridge.sourceforge.net/
endef
+define Package/bridge/description
+ Manage ethernet bridging:
+ a way to connect networks together to form a larger network.
+endef
+
define Build/Configure
$(call Build/Configure/Default, \
--with-linux-headers="$(LINUX_DIR)" \
Contains all environment variables that are passed to the make command
\end{itemize}
+\textbf{\texttt{Build/InstallDev} (optional):} \\
+ If your package provides a library that needs to be made available to other packages,
+ you can use the \texttt{Build/InstallDev} template to copy it into the staging directory
+ which is used to collect all files that other packages might depend on at build time.
+ When it is called by the build system, two parameters are passed to it. \texttt{\$(1)} points to
+ the regular staging dir, typically \texttt{staging\_dir/\textit{ARCH}}, while \texttt{\$(2)} points
+ to \texttt{staging\_dir/host}. The host staging dir is only used for binaries, which are
+ to be executed or linked against on the host and its \texttt{bin/} subdirectory is included
+ in the \texttt{PATH} which is passed down to the build system processes.
+ Please use \texttt{\$(1)} and \texttt{\$(2)} here instead of the build system variables
+ \texttt{\$(STAGING\_DIR)} and \texttt{\$(STAGING\_DIR\_HOST)}, because the build system behavior
+ when staging libraries might change in the future to include automatic uninstallation.
+
\textbf{\texttt{Package/\textit{<name>}/install}:} \\
A set of commands to copy files out of the compiled source and into the ipkg
which is represented by the \texttt{\$(1)} directory. Note that there are currently
will automatically show in the menu the next time you run "make menuconfig" and if selected
will be built automatically the next time "\texttt{make}" is run.
+\subsection{Creating kernel modules packages}
+
+The OpenWrt distribution makes the distinction between two kind of kernel modules, those coming along with the mainline kernel, and the others available as a separate project. We will see later that a common template is used for both of them.
+
+For kernel modules that are part of the mainline kernel source, the makefiles are located in \textit{package/kernel/modules/*.mk} and they appear under the section "Kernel modules"
+
+For external kernel modules, you can add them to the build system just like if they were software packages by defining a KernelPackage section in the package makefile.
+
+Here for instance the Makefile for the I2C subsytem kernel modules :
+
+\begin{Verbatim}[frame=single,numbers=left]
+# $Id $
+
+I2CMENU:=I2C Bus
+
+define KernelPackage/i2c-core
+ TITLE:=I2C support
+ DESCRIPTION:=Kernel modules for i2c support
+ SUBMENU:=$(I2CMENU)
+ KCONFIG:=CONFIG_I2C_CORE CONFIG_I2C_DEV
+ FILES:=$(MODULES_DIR)/kernel/drivers/i2c/*.$(LINUX_KMOD_SUFFIX)
+ AUTOLOAD:=$(call AutoLoad,50,i2c-core i2c-dev)
+endef
+$(eval $(call KernelPackage,i2c-core))
+\end{Verbatim}
+
+To group kernel modules under a common description in menuconfig, you might want to define a \textit{<description>MENU} variable on top of the kernel modules makefile.
+
+\begin{itemize}
+ \item \texttt{TITLE} \\
+ The name of the module as seen via menuconfig
+ \item \texttt{DESCRIPTION} \\
+ The description as seen via help in menuconfig
+ \item \texttt{SUBMENU} \\
+ The sub menu under which this package will be seen
+ \item \texttt{KCONFIG} \\
+ Kernel configuration option dependency. For external modules, remove it.
+ \item \texttt{FILES} \\
+ Files you want to inlude to this kernel module package, separate with spaces.
+ \item \texttt{AUTOLOAD} \\
+ Modules that will be loaded automatically on boot, the order you write them is the order they would be loaded.
+\end{itemize}
+
+After you have created your \texttt{package/kernel/modules/\textit{<name>}.mk}, the new kernel modules package
+will automatically show in the menu under "Kernel modules" next time you run "make menuconfig" and if selected
+will be built automatically the next time "\texttt{make}" is run.
\subsection{Conventions}
run one of the following:
\begin{itemize}
- \item \texttt{make package/\textit{<name>}-clean V=99}
- \item \texttt{make package/\textit{<name>}-install V=99}
+ \item \texttt{make package/\textit{<name>}/clean V=99}
+ \item \texttt{make package/\textit{<name>}/install V=99}
\end{itemize}
-Another nice trick is that if the source directory under \texttt{build\_\textit{<arch>}}
+Another nice trick is that if the source directory under \texttt{build\_
dir/\textit{<arch>}}
is newer than the package directory, it won't clobber it by unpacking the sources again.
If you were working on a patch you could simply edit the sources under the
-\texttt{build\_\textit{<arch>}/\textit{<source>}} directory and run the install command above,
+\texttt{build\_
dir/\textit{<arch>}/\textit{<source>}} directory and run the install command above,
when satisfied, copy the patched sources elsewhere and diff them with the unpatched
sources. A warning though - if you go modify anything under \texttt{package/\textit{<name>}}
it will remove the old sources and unpack a fresh copy.
Other useful targets include:
\begin{itemize}
- \item \texttt{make package/\textit{<name>}-prepare V=99}
- \item \texttt{make package/\textit{<name>}-compile V=99}
- \item \texttt{make package/\textit{<name>}-configure V=99}
+ \item \texttt{make package/\textit{<name>}/prepare V=99}
+ \item \texttt{make package/\textit{<name>}/compile V=99}
+ \item \texttt{make package/\textit{<name>}/configure V=99}
\end{itemize}
+
+\subsection{Using build environments}
+OpenWrt provides a means of building images for multiple configurations
+which can use multiple targets in one single checkout. These \emph{environments}
+store a copy of the .config file generated by \texttt{make menuconfig} and the contents
+of the \texttt{./files} folder.
+The script \texttt{./scripts/env} is used to manage these environments, it uses
+\texttt{git} (which needs to be installed on your system) as backend for version control.
+
+The command
+\begin{Verbatim}
+ \texttt{./scripts/env help}
+\end{Verbatim}
+produces a short help text with a list of commands.
+
+To create a new environment named \texttt{current}, run the following command
+\begin{Verbatim}
+ ./scripts/env new current
+\end{Verbatim}
+This will move your \texttt{.config} file and \texttt{./files} (if it exists) to
+the \texttt{env/} subdirectory and create symlinks in the base folder.
+
+After running make menuconfig or changing things in files/, your current state will
+differ from what has been saved before. To show these changes, use:
+\begin{Verbatim}
+ ./scripts/env diff
+\end{Verbatim}
+
+If you want to save these changes, run:
+\begin{Verbatim}
+ ./scripts/env save
+\end{Verbatim}
+If you want to revert your changes to the previously saved copy, run:
+\begin{Verbatim}
+ ./scripts/env revert
+\end{Verbatim}
+
+If you want, you can now create a second environment using the \texttt{new} command.
+It will ask you whether you want to make it a clone of the current environment (e.g.
+for minor changes) or if you want to start with a clean version (e.g. for selecting
+a new target).
+
+To switch to a different environment (e.g. \texttt{test1}), use:
+\begin{Verbatim}
+ ./scripts/env switch test1
+\end{Verbatim}
+
+To rename the current branch to a new name (e.g. \texttt{test2}), use:
+\begin{Verbatim}
+ ./scripts/env rename test2
+\end{Verbatim}
+
+If you want to get rid of environment switching and keep everything in the base directory
+again, use:
+\begin{Verbatim}
+ ./scripts/env clear
+\end{Verbatim}
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