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)" \
\textbf{\texttt{Build/Compile} (optional):} \\
How to compile the source; in most cases you should leave this undefined.
+
+ As with \texttt{Build/Configure} there are two variables that allow you to override
+ the make command line environment variables and flags:
+ \begin{itemize}
+ \item \texttt{MAKE\_FLAGS} \\
+ Contains all command line arguments (typically variable overrides like \texttt{NAME="value"}
+ \item \texttt{MAKE\_VARS} \\
+ 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
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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