\subsubsection{Amount of flash memory}
-Linux can hardly fit in a 2MB flash device, once you have open the device and
-located the flash chip, try to find other the Internet its characteristics. If
+Linux can hardly fit in a 2MB flash device, once you have opened the device and
+located the flash chip, try to find its characteristics on the Internet. If
your flash chip is a 2MB or less device, your device is most likely to run a
proprietary OS such as WindRiver VxWorks, or a custom manufacturer OS like Zyxel ZynOS.
-OpenWrt does not currently run on devices which have equal or less than 2MB of
-flash memory. This limitation will probably not be worked around since those
-devices are most of the time micro routers, or Wireless Access Points, which are
-not the main OpenWrt target.
+OpenWrt does not currently run on devices which have 2MB or less of flash memory.
+This limitation will probably not be worked around since those devices are most
+of the time micro-routers, or Wireless Access Points, which are not the main
+OpenWrt target.
\subsubsection{Pluging a serial port}
-By using a serial port, you may reach the console that is being shown by the device
+By using a serial port and a level shifter, you may reach the console that is being shown by the device
for debugging or flashing purposes. By analysing the output of this device, you can
easily notice if the device uses a Linux kenrel or something different.
\subsection{Finding and using the manufacturer SDK}
Once you are sure your device run a Linux based firmware, you will be able to start
-hacking on it. If the manufacturer respect the GPL, it will have release with the
-device, a Sample Development Kit.
+hacking on it. If the manufacturer respected the GPL, it will have released a Sample
+Development Kit with the device.
\subsubsection{GPL violations}
\item binary tools to create a valid firmware image
\end{itemize}
-Your work is now divided into the following tasks:
+Your work can be divided into the following tasks:
\begin{itemize}
\item create a clean patch of the hardware specific part of the linux kernel
-\item spot potential kernel GPL violations especially on firewall and USB stack stuff
+\item spot potential kernel GPL violations especially on netfilter and USB stack stuff
\item make the binary drivers work, until there are open source drivers
\item use standard a GNU toolchain to make working executables
\item understand and write open source tools to generate a valid firmware image
specific fixes.
The second patch will contain all useful definitions for that board: adresses,
-kernel granularity, redifinitions, processor family and features ...
+kernel granularity, redefinitions, processor family and features ...
The third patch may contain drivers for: serial console, ethernet NIC, wireless
NIC, USB NIC ... Most of the time this patch contains nothing else than "glue"
code that has been added to make the binary driver work with the Linux kernel.
-This code might not be useful if you plan on writing from scratch drivers for
+This code might not be useful if you plan on writing drivers from scratch for
this hardware.
\subsubsection{Using the device bootloader}
do network booting, USB mass storage booting ... The bootloader is device and
architeture specific, some bootloaders were designed to be universal such as
RedBoot or U-Boot so that you can meet those loaders on totally different
-platforms and expect to work the same way.
+platforms and expect them to behave the same way.
If your device runs a proprietary operating system, you are very likely to deal
with a proprietary boot loader as well. This may not always be a limitation,
some proprietary bootloaders can even have source code available (i.e : Broadcom CFE).
-According to the bootloader features, hacking on th device will be more or less
+According to the bootloader features, hacking on the device will be more or less
easier. It is very probable that the bootloader, even exotic and rare, has a
documentation somewhere over the Internet. In order to know what will be possible
with your bootloader and the way you are going to hack the device, look over the
\item CONFIG\_DEBUG\_KERNEL
\item CONFIG\_DETECT\_SOFTLOCKUP
\item CONFIG\_DEBUG\_KOBJECT
-\item CONFIG\_EMBEDDED
\item CONFIG\_KALLSYMS
\item CONFIG\_KALLSYMS\_ALL
\end{itemize}
\begin{itemize}
\item header, containing a firmare version and additional fields: Vendor, Hardware version ...
\item CRC32 checksum on either the whole file or just part of it
-\item Binary or compressed kernel image
-\item Binary or compressed root filesystem image
+\item Binary and/or compressed kernel image
+\item Binary and/or compressed root filesystem image
\item potential garbage
\end{itemize}
that covers the case of the device where the bootloader can pass to the kernel its partition plan.
First of all, you need to make your flash map driver be visible in the kernel
-configuration options, this can be done by editing the file
+configuration options, this can be done by editing the file \
\textbf{linux/drivers/mtd/maps/Kconfig}:
\begin{verbatim}
projects / openwrt.git / blobdiff