root/trunk/freewrt/target/target.tex

\section{Target Compilation}

The following section will discuss how kernel and root filesystem are being
created and packed into appropriate formats for use with each target device.

\subsection{Kernel Compilation}

\subsubsection{General Kernel Cross Compiling Guide}

The Linux kernel supports being cross compiled for various architectures. For a
list of currently supported machine types, see the \file{arch/} subdirectory of
the kernel sources.

There are some prerequisites that need to be fulfilled:
\begin{itemize}
        \item the directory containing the cross-toolchain must be contained in
                your \$\{PATH\} environment variable (best choice is at last position)
        \item \command{make} needs to be called with \code{ARCH=MYARCH} as
                parameter, while \code{MYARCH} must be substituted with the
                destined architecture
        \item if necessary, one can also specify \code{CROSS\_COMPILE=PFX} as
                additional argument to \command{make}, where \code{PFX} is
                something like \code{mipsel-linux-} (defaults to
                \code{\$\{ARCH\}-linux-})
\end{itemize}

Then configuring and compiling is straight forward:
\begin{Verbatim}[label=kernel cross compiling]
$ make ARCH=mips menuconfig
[...]
$ make ARCH=mips
\end{Verbatim}

\subsubsection{How The ADK Builds A Kernel}

\begin{itemize}
\item destined kernel version via makefile include from inside \file{target/linux/\$\{BOARD\}-2.\{4,6\}/Makefile}
\item kernel .config creation:  \file{target/Makefile}
\item howto update the static kernel config
\item kernel compilation (output of files, etc.)
\end{itemize}

\subsection{Image Creation}

\begin{itemize}
\item different image formats
\item image creation process for each format
\item kernel vs. nokernel targets
\end{itemize}

\subsection{Adding A New Kernel Version}

FreeWRT supports using a different kernel version for each target device. This
way it is possible to update the kernel used for one's favourite device without
(possibly) breaking all others using the same kernel major.

\begin{enumerate}
        \item create a new subdirectory
                \file{target/linux/generic-\$\{KERNEL\_VERSION\}}
        \item copy over and adapt a \file{Makefile} from one of the existing
                subdirectories, basically updating the MD5 sum (the ADK fetches
                the \file{tar.bz2} version)
        \item update \$\{UNAME\_R\} for your device in \file{rules.mk}
        \item make sure
                \file{target/linux/\$\{BOARD\}-\$\{KERNEL\_MAJOR\}/Makefile}
                includes the right files
        \item update the static kernel config provided for your device
                %TODO: hint to the docs about it in this file, using \ref
\end{enumerate}

%\subsection{Updating The Static Kernel Config For A Device}

%\subsection{Adding A New Target Device}

% - target/linux/bla-2.X/{Config.in,Makefile} erstellen
% - target/linux/bla-2.X/patches befuellen (meistens)
% - target/linux/bla-2.X/kernelconfig erstellen (\ref)
% - target/Config.in erweitern
% - mk/targets.mk erweitern
%   - target_template
%   - arch-definition (optional)
% - target/image/bla erstellen
%   - Makefile aus target/image/rb/Makefile (oder so), anpassen