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}
trunk and can be obtained from subversion at the following location:
\begin{Verbatim}
-$ svn co https://svn.openwrt.org/openwrt/packages ../packages
+$ svn checkout https://svn.openwrt.org/openwrt/packages packages
\end{Verbatim}
Those packages can be used to extend the functionality of the build system and need to be
$ ln -s packages/*/* kamikaze/package/
\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>}}"
\end{itemize}
After you've finished with the menu configuration, exit and when prompted, save your
-configuration changes. To begin compiling the firmware, type "\texttt{make}". By default
+configuration changes.
+
+If you want, you can also modify the kernel config for the selected target system.
+simply run "\texttt{make kernel\_menuconfig}" and the build system will unpack the kernel sources
+(if necessary), run menuconfig inside of the kernel tree, and then copy the kernel config
+to \texttt{target/linux/\textit{<platform>}/config} so that it is preserved over
+"\texttt{make clean}" calls.
+
+To begin compiling the firmware, type "\texttt{make}". By default
OpenWrt will only display a high level overview of the compile process and not each individual
command.
\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
\item \texttt{MAINTAINER} (optional) \\
Who to contact concerning the package
\item \texttt{DEPENDS} (optional) \\
- Which packages must be built/installed before this package. To reference a dependency defined in the same Makefile, use \textit{<dependency name>}. If defined as an external package, use \textit{+<dependency name>}. For a kernel version dependency use: \textit{@LINUX\_2\_<minor version>}
+ Which packages must be built/installed before this package. To reference a dependency defined in the
+ same Makefile, use \textit{<dependency name>}. If defined as an external package, use
+ \textit{+<dependency name>}. For a kernel version dependency use: \textit{@LINUX\_2\_<minor version>}
\end{itemize}
\textbf{\texttt{Package/\textit{<name>}/conffiles} (optional):} \\
You can leave this undefined if the source doesn't use configure or has a
normal config script, otherwise you can put your own commands here or use
"\texttt{\$(call Build/Configure/Default,\textit{<first list of arguments, second list>})}" as above to
- pass in additional arguments for a standard configure script. The first list of arguments will be passed to the configure script like that: $--arg 1$ $--arg 2$. The second list contains arguments that should be defined before running the configure script such as autoconf or compiler specific variables.
+ pass in additional arguments for a standard configure script. The first list of arguments will be passed
+ to the configure script like that: \texttt{--arg 1} \texttt{--arg 2}. The second list contains arguments that should be
+ defined before running the configure script such as autoconf or compiler specific variables.
+
+ To make it easier to modify the configure command line, you can either extend or completely override the following variables:
+ \begin{itemize}
+ \item \texttt{CONFIGURE\_ARGS} \\
+ Contains all command line arguments (format: \texttt{--arg 1} \texttt{--arg 2})
+ \item \texttt{CONFIGURE\_VARS} \\
+ Contains all environment variables that are passed to ./configure (format: \texttt{NAME="value"})
+ \end{itemize}
\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{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]
+#
+# Copyright (C) 2006 OpenWrt.org
+#
+# This is free software, licensed under the GNU General Public License v2.
+# See /LICENSE for more information.
+#
+# $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}
projects / openwrt.git / blobdiff