# MCU name
MCU = atmega32u4

# Bootloader selection
#   Teensy       halfkay
#   Pro Micro    caterina
#   Atmel DFU    atmel-dfu
#   LUFA DFU     lufa-dfu
#   QMK DFU      qmk-dfu
#   ATmega32A    bootloadHID
#   ATmega328P   USBasp
BOOTLOADER = atmel-dfu

# Build Options
#   change yes to no to disable
#
BOOTMAGIC_ENABLE = no      # Virtual DIP switch configuration(+1000)
MOUSEKEY_ENABLE = yes       # Mouse keys(+4700)
EXTRAKEY_ENABLE = yes       # Audio control and System control(+450)
CONSOLE_ENABLE = no        # Console for debug(+400)
COMMAND_ENABLE = no        # Commands for debug and configuration
# Do not enable SLEEP_LED_ENABLE. it uses the same timer as BACKLIGHT_ENABLE
SLEEP_LED_ENABLE = no       # Breathing sleep LED during USB suspend
# if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
NKRO_ENABLE = yes           # USB Nkey Rollover
BACKLIGHT_ENABLE = yes       # Enable keyboard backlight functionality on B7 by default
RGBLIGHT_ENABLE = yes
MIDI_ENABLE = no            # MIDI controls
UNICODE_ENABLE = no         # Unicode
BLUETOOTH_ENABLE = no       # Enable Bluetooth with the Adafruit EZ-Key HID
AUDIO_ENABLE = no           # Audio output on port C6
master</option>
<option value='master'>master</option>
<option value='old-master'>old-master</option>
<option value='openwrt-18.06'>openwrt-18.06</option>
<option value='openwrt-19.07'>openwrt-19.07</option>
<option value='upstream'>upstream</option>
</select> <input type='submit' value='switch'/></form></td></tr>
<tr><td class='sub'>upstream openwrt</td><td class='sub right'>James</td></tr></table>
<table class='tabs'><tr><td>
<a href='/cgit.cgi/openwrt/upstream/about/?h=v22.03.0-rc6'>about</a><a href='/cgit.cgi/openwrt/upstream/?h=v22.03.0-rc6'>summary</a><a href='/cgit.cgi/openwrt/upstream/refs/?h=v22.03.0-rc6&amp;id=7fd85258534035f8eae91f2737a2b0f3f532ebaf'>refs</a><a href='/cgit.cgi/openwrt/upstream/log/docs/adding.tex?h=v22.03.0-rc6'>log</a><a class='active' href='/cgit.cgi/openwrt/upstream/tree/docs/adding.tex?h=v22.03.0-rc6&amp;id=7fd85258534035f8eae91f2737a2b0f3f532ebaf'>tree</a><a href='/cgit.cgi/openwrt/upstream/commit/docs/adding.tex?h=v22.03.0-rc6&amp;id=7fd85258534035f8eae91f2737a2b0f3f532ebaf'>commit</a><a href='/cgit.cgi/openwrt/upstream/diff/docs/adding.tex?h=v22.03.0-rc6&amp;id=7fd85258534035f8eae91f2737a2b0f3f532ebaf'>diff</a><a href='/cgit.cgi/openwrt/upstream/stats/docs/adding.tex?h=v22.03.0-rc6'>stats</a></td><td class='form'><form class='right' method='get' action='/cgit.cgi/openwrt/upstream/log/docs/adding.tex'>
<input type='hidden' name='h' value='v22.03.0-rc6'/><input type='hidden' name='id' value='7fd85258534035f8eae91f2737a2b0f3f532ebaf'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/cgit.cgi/openwrt/upstream/tree/?h=v22.03.0-rc6&amp;id=7fd85258534035f8eae91f2737a2b0f3f532ebaf'>root</a>/<a href='/cgit.cgi/openwrt/upstream/tree/docs?h=v22.03.0-rc6&amp;id=7fd85258534035f8eae91f2737a2b0f3f532ebaf'>docs</a>/<a href='/cgit.cgi/openwrt/upstream/tree/docs/adding.tex?h=v22.03.0-rc6&amp;id=7fd85258534035f8eae91f2737a2b0f3f532ebaf'>adding.tex</a></div><div class='content'>blob: 97547ac859458ba58361b9be0e85fba62ecb9e9c (<a href='/cgit.cgi/openwrt/upstream/plain/docs/adding.tex?h=v22.03.0-rc6&amp;id=7fd85258534035f8eae91f2737a2b0f3f532ebaf'>plain</a>)
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.highlight .il { color: #0000DD; font-weight: bold } /* Literal.Number.Integer.Long */</style><div class="highlight"><pre><span></span>Linux is now one of the most widespread operating system for embedded devices due
to its openess as well as the wide variety of platforms it can run on. Many
manufacturer actually use it in firmware you can find on many devices: DVB-T 
decoders, routers, print servers, DVD players ... Most of the time the stock 
firmware is not really open to the consumer, even if it uses open source software.

You might be interested in running a Linux based firmware for your router for
various reasons: extending the use of a network protocol (such as IPv6), having
new features, new piece of software inside, or for security reasons. A fully 
open-source firmware is de-facto needed for such applications, since you want to
be free to use this or that version of a particular reason, be able to correct a
particular bug. Few manufacturers do ship their routers with a Sample Development Kit,
that would allow you to create your own and custom firmware and most of the time,
when they do, you will most likely not be able to complete the firmware creation process.

This is one of the reasons why OpenWrt and other firmware exists: providing a 
version independent, and tools independent firmware, that can be run on various 
platforms, known to be running Linux originally.

<span class="k">\subsection</span><span class="nb">{</span>Which Operating System does this device run?<span class="nb">}</span>

There is a lot of methods to ensure your device is running Linux. Some of them do
need your router to be unscrewed and open, some can be done by probing the device
using its external network interfaces.

<span class="k">\subsubsection</span><span class="nb">{</span>Operating System fingerprinting and port scanning<span class="nb">}</span>

A large bunch of tools over the Internet exists in order to let you do OS 
fingerprinting, we will show here an example using <span class="k">\textbf</span><span class="nb">{</span>nmap<span class="nb">}</span>:

<span class="k">\begin</span><span class="nb">{</span>Verbatim<span class="nb">}</span>
nmap -P0 -O &lt;IP address&gt;
Starting Nmap 4.20 ( http://insecure.org ) at 2007-01-08 11:05 CET
Interesting ports on 192.168.2.1:
Not shown: 1693 closed ports
PORT   STATE SERVICE
22/tcp open  ssh
23/tcp open  telnet
53/tcp open  domain
80/tcp open  http
MAC Address: 00:13:xx:xx:xx:xx (Cisco-Linksys)
Device type: broadband router
Running: Linksys embedded
OS details: Linksys WRT54GS v4 running OpenWrt w/Linux kernel 2.4.30
Network Distance: 1 hop
<span class="k">\end</span><span class="nb">{</span>Verbatim<span class="nb">}</span>

nmap is able to report whether your device uses a Linux TCP/IP stack, and if so,
will show you which Linux kernel version is probably runs. This report is quite 
reliable and it can make the distinction between BSD and Linux TCP/IP stacks and others.

Using the same tool, you can also do port scanning and service version discovery.
For instance, the following command will report which IP-based services are running
on the device, and which version of the service is being used:

<span class="k">\begin</span><span class="nb">{</span>verbatim<span class="nb">}</span>
nmap -P0 -sV &lt;IP address&gt;
Starting Nmap 4.20 ( http://insecure.org ) at 2007-01-08 11:06 CET
Interesting ports on 192.168.2.1:
Not shown: 1693 closed ports
PORT   STATE SERVICE VERSION
22/tcp open  ssh     Dropbear sshd 0.48 (protocol 2.0)
23/tcp open  telnet  Busybox telnetd
53/tcp open  domain  ISC Bind dnsmasq-2.35
80/tcp open  http    OpenWrt BusyBox httpd
MAC Address: 00:13:xx:xx:xx:xx (Cisco-Linksys)
Service Info: Device: WAP
<span class="k">\end</span><span class="nb">{</span>verbatim<span class="nb">}</span>

The web server version, if identified, can be determining in knowing the Operating
System. For instance, the <span class="k">\textbf</span><span class="nb">{</span>BOA<span class="nb">}</span> web server is typical from devices running 
an open-source Unix or Unix-like.

<span class="k">\subsubsection</span><span class="nb">{</span>Wireless Communications Fingerprinting<span class="nb">}</span>

Although this method is not really known and widespread, using a wireless scanner 
to discover which OS your router or Access Point run can be used. We do not have
a clear example of how this could be achieved, but you will have to monitor raw 
802.11 frames and compare them to a very similar device running a Linux based firmware.

<span class="k">\subsubsection</span><span class="nb">{</span>Web server security exploits<span class="nb">}</span>

The Linksys WRT54G was originally hacked by using a &quot;ping bug&quot; discovered in the 
web interface. This tip has not been fixed for months by Linksys, allowing people
to enable the &quot;boot<span class="k">\_</span>wait&quot; helper process via the web interface. Many web servers
used in firmwares are open source web server, thus allowing the code to be audited
to find an exploit. Once you know the web server version that runs on your device,
by using <span class="k">\textbf</span><span class="nb">{</span>nmap -sV<span class="nb">}</span> or so, you might be interested in using exploits to reach 
shell access on your device.

<span class="k">\subsubsection</span><span class="nb">{</span>Native Telnet/SSH access<span class="nb">}</span>

Some firmwares might have restricted or unrestricted Telnet/SSH access, if so,
try to log in with the web interface login/password and see if you can type in 
some commands. This is actually the case for some Broadcom BCM963xx based firmwares
such as the one in Neuf/Cegetel ISP routers, Club-Internet ISP CI-Box and many 
others. Some commands, like <span class="k">\textbf</span><span class="nb">{</span>cat<span class="nb">}</span> might be left here and be used to 
determine the Linux kernel version.

<span class="k">\subsubsection</span><span class="nb">{</span>Analysing a binary firmware image<span class="nb">}</span>

You are very likely to find a firmware binary image on the manufacturer website,
even if your device runs a proprietary operating system. If so, you can download
it and use an hexadecimal editor to find printable words such as <span class="k">\textbf</span><span class="nb">{</span>vmlinux<span class="nb">}</span>,
<span class="k">\textbf</span><span class="nb">{</span>linux<span class="nb">}</span>, <span class="k">\textbf</span><span class="nb">{</span>ramdisk<span class="nb">}</span>, <span class="k">\textbf</span><span class="nb">{</span>mtd<span class="nb">}</span> and others.

Some Unix tools like <span class="k">\textbf</span><span class="nb">{</span>hexdump<span class="nb">}</span> or <span class="k">\textbf</span><span class="nb">{</span>strings<span class="nb">}</span> can be used to analyse 
the firmware. Below there is an example with a binary firmware found other the Internet:

<span class="k">\begin</span><span class="nb">{</span>verbatim<span class="nb">}</span>
hexdump -C &lt;binary image.extension&gt; | less (more)
00000000  46 49 52 45 32 2e 35 2e  30 00 00 00 00 00 00 00  |FIRE2.5.0.......|
00000010  00 00 00 00 31 2e 30 2e  30 00 00 00 00 00 00 00  |....1.0.0.......|
00000020  00 00 00 00 00 00 00 38  00 43 36 29 00 0a e6 dc  |.......8.C6)..??|
00000030  54 49 44 45 92 89 54 66  1f 8b 08 08 f8 10 68 42  |TIDE..Tf....?.hB|
00000040  02 03 72 61 6d 64 69 73  6b 00 ec 7d 09 bc d5 d3  |..ramdisk.?<span class="nb">}</span>.???|
00000050  da ff f3 9b f7 39 7b ef  73 f6 19 3b 53 67 ea 44  |???.?9<span class="nb">{</span>?s?.;Sg?D|
<span class="k">\end</span><span class="nb">{</span>verbatim<span class="nb">}</span>

Scroll over the firmware to find printable words that can be significant.

<span class="k">\subsubsection</span><span class="nb">{</span>Amount of flash memory<span class="nb">}</span>

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 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.

<span class="k">\subsubsection</span><span class="nb">{</span>Pluging a serial port<span class="nb">}</span>

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 kernel or something different.

<span class="k">\subsection</span><span class="nb">{</span>Finding and using the manufacturer SDK<span class="nb">}</span>

Once you are sure your device run a Linux based firmware, you will be able to start
hacking on it. If the manufacturer respected the GPL, it will have released a Sample
Development Kit with the device.

<span class="k">\subsubsection</span><span class="nb">{</span>GPL violations<span class="nb">}</span>

Some manufacturers do release a Linux based binary firmware, with no sources at all.
The first step before doing anything is to read the license coming with your device,
then write them about this lack of Open Source code. If the manufacturer answers
you they do not have to release a SDK containing Open Source software, then we 
recommend you get in touch with the gpl-violations.org community.

You will find below a sample letter that can be sent to the manufacturer:

<span class="k">\begin</span><span class="nb">{</span>verse<span class="nb">}</span>
Miss, Mister,

I am using a &lt;device name&gt;, and I cannot find neither on your website nor on the 
CD-ROM the open source software used to build or modify the firmware.

In conformance to the GPL license, you have to release the following sources:

<span class="k">\begin</span><span class="nb">{</span>itemize<span class="nb">}</span>
<span class="k">\item</span> complete toolchain that made the kernel and applications be compiled (gcc, binutils, libc)
<span class="k">\item</span> tools to build a custom firmware (mksquashfs, mkcramfs ...)
<span class="k">\item</span> kernel sources with patches to make it run on this specific hardware, this does not include binary drivers
<span class="k">\end</span><span class="nb">{</span>itemize<span class="nb">}</span>

Thank you very much in advance for your answer.

Best regards, &lt;your name&gt;
<span class="k">\end</span><span class="nb">{</span>verse<span class="nb">}</span>

<span class="k">\subsubsection</span><span class="nb">{</span>Using the SDK<span class="nb">}</span>

Once the SDK is available, you are most likely not to be able to build a complete
or functional firmware using it, but parts of it, like only the kernel, or only
the root filesystem. Most manufacturers do not really care releasing a tool that
do work every time you uncompress and use it.

You should anyway be able to use the following components:

<span class="k">\begin</span><span class="nb">{</span>itemize<span class="nb">}</span>
<span class="k">\item</span> kernel sources with more or less functional patches for your hardware
<span class="k">\item</span> binary drivers linked or to be linked with the shipped kernel version
<span class="k">\item</span> packages of the toolchain used to compile the whole firmware: gcc, binutils, libc or uClibc
<span class="k">\item</span> binary tools to create a valid firmware image
<span class="k">\end</span><span class="nb">{</span>itemize<span class="nb">}</span>

Your work can be divided into the following tasks:

<span class="k">\begin</span><span class="nb">{</span>itemize<span class="nb">}</span>
<span class="k">\item</span> create a clean patch of the hardware specific part of the linux kernel
<span class="k">\item</span> spot potential kernel GPL violations especially on netfilter and USB stack stuff
<span class="k">\item</span> make the binary drivers work, until there are open source drivers
<span class="k">\item</span> use standard a GNU toolchain to make working executables
<span class="k">\item</span> understand and write open source tools to generate a valid firmware image
<span class="k">\end</span><span class="nb">{</span>itemize<span class="nb">}</span>

<span class="k">\subsubsection</span><span class="nb">{</span>Creating a hardware specific kernel patch<span class="nb">}</span>

Most of the time, the kernel source that comes along with the SDK is not really 
clean, and is not a standard Linux version, it also has architecture specific 
fixes backported from the <span class="k">\textbf</span><span class="nb">{</span>CVS<span class="nb">}</span> or the <span class="k">\textbf</span><span class="nb">{</span>git<span class="nb">}</span> repository of the 
kernel development trees. Anyway, some parts can be easily isolated and used as 
a good start to make a vanilla kernel work your hardware.

Some directories are very likely to have local modifications needed to make your
hardware be recognized and used under Linux. First of all, you need to find out 
the linux kernel version that is used by your hardware, this can be found by 
editing the <span class="k">\textbf</span><span class="nb">{</span>linux/Makefile<span class="nb">}</span> file.

<span class="k">\begin</span><span class="nb">{</span>verbatim<span class="nb">}</span>
head -5 linux-2.x.x/Makefile
VERSION = 2
PATCHLEVEL = x
SUBLEVEL = y
EXTRAVERSION = z
NAME=A fancy name
<span class="k">\end</span><span class="nb">{</span>verbatim<span class="nb">}</span>

So now, you know that you have to download a standard kernel tarball at 
<span class="k">\textbf</span><span class="nb">{</span>kernel.org<span class="nb">}</span> that matches the version being used by your hardware.

Then you can create a <span class="k">\textbf</span><span class="nb">{</span>diff<span class="nb">}</span> file between the two trees, especially for the 
following directories:

<span class="k">\begin</span><span class="nb">{</span>verbatim<span class="nb">}</span>
diff -urN linux-2.x.x/arch/&lt;sub architecture&gt; linux-2.x.x-modified/arch/&lt;sub architecture&gt; &gt; 01-architecture.patch
diff -urN linux-2.x.x/include/ linux-2.x.x-modified/include &gt; 02-includes.patch
diff -urN linux-2.x.x/drivers/ linux-2.x.x-modified/drivers &gt; 03-drivers.patch
<span class="k">\end</span><span class="nb">{</span>verbatim<span class="nb">}</span>

This will constitute a basic set of three patches that are very likely to contain
any needed modifications that has been made to the stock Linux kernel to run on 
your specific device. Of course, the content produced by the <span class="k">\textbf</span><span class="nb">{</span>diff -urN<span class="nb">}</span> 
may not always be relevant, so that you have to clean up those patches to only 
let the &quot;must have&quot; code into them.

The first patch will contain all the code that is needed by the board to be 
initialized at startup, as well as processor detection and other boot time 
specific fixes.

The second patch will contain all useful definitions for that board: addresses, 
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 &quot;glue&quot;
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 drivers from scratch for 
this hardware.

<span class="k">\subsubsection</span><span class="nb">{</span>Using the device bootloader<span class="nb">}</span>

The bootloader is the first program that is started right after your device has 
been powered on. This program, can be more or less sophisticated, some do let you 
do network booting, USB mass storage booting ... The bootloader is device and 
architecture 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 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 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 
following features :

<span class="k">\begin</span><span class="nb">{</span>itemize<span class="nb">}</span>
<span class="k">\item</span> does the bootloader allow net booting via bootp/DHCP/NFS or tftp
<span class="k">\item</span> does the bootloader accept loading ELF binaries ?
<span class="k">\item</span> does the bootloader have a kernel/firmware size limitation ?
<span class="k">\item</span> does the bootloader expect a firmware format to be loaded with ?
<span class="k">\item</span> are the loaded files executed from RAM or flash ?
<span class="k">\end</span><span class="nb">{</span>itemize<span class="nb">}</span>

Net booting is something very convenient, because you will only have to set up network
booting servers on your development station, and keep the original firmware on the device
till you are sure you can replace it. This also prevents your device from being flashed,
and potentially bricked every time you want to test a modification on the kernel/filesystem.

If your device needs to be flashed every time you load a firmware, the bootlader might
only accept a specific firmware format to be loaded, so that you will have to 
understand the firmware format as well.

<span class="k">\subsubsection</span><span class="nb">{</span>Making binary drivers work<span class="nb">}</span>

As we have explained before, manufacturers do release binary drivers in their GPL
tarball. When those drivers are statically linked into the kernel, they become GPL
as well, fortunately or unfortunately, most of the drivers are not statically linked.
This anyway lets you a chance to dynamically link the driver with the current kernel
version, and try to make them work together.

This is one of the most tricky and grey part of the fully open source projects. 
Some drivers require few modifications to be working with your custom kernel, 
because they worked with an earlier kernel, and few modifications have been made
to the kernel in-between those versions. This is for instance the case with the 
binary driver of the Broadcom BCM43xx Wireless Chipsets, where only few differences
were made to the network interface structures.

Some general principles can be applied no matter which kernel version is used in
order to make binary drivers work with your custom kernel:

<span class="k">\begin</span><span class="nb">{</span>itemize<span class="nb">}</span>
<span class="k">\item</span> turn on kernel debugging features such as:
<span class="k">\begin</span><span class="nb">{</span>itemize<span class="nb">}</span>
<span class="k">\item</span> CONFIG<span class="k">\_</span>DEBUG<span class="k">\_</span>KERNEL
<span class="k">\item</span> CONFIG<span class="k">\_</span>DETECT<span class="k">\_</span>SOFTLOCKUP
<span class="k">\item</span> CONFIG<span class="k">\_</span>DEBUG<span class="k">\_</span>KOBJECT
<span class="k">\item</span> CONFIG<span class="k">\_</span>KALLSYMS
<span class="k">\item</span> CONFIG<span class="k">\_</span>KALLSYMS<span class="k">\_</span>ALL
<span class="k">\end</span><span class="nb">{</span>itemize<span class="nb">}</span>
<span class="k">\item</span> link binary drivers when possible to the current kernel version
<span class="k">\item</span> try to load those binary drivers
<span class="k">\item</span> catch the lockups and understand them
<span class="k">\end</span><span class="nb">{</span>itemize<span class="nb">}</span>

Most of the time, loading binary drivers will fail, and generate a kernel oops. 
You can know the last symbol the binary drivers attempted to use, and see in the
kernel headers file, if you do not have to move some structures field before or 
after that symbol in order to keep compatibily with both the binary driver and 
the stock kernel drivers.

<span class="k">\subsubsection</span><span class="nb">{</span>Understanding the firmware format<span class="nb">}</span>

You might want to understand the firmware format, even if you are not yet capable
of running a custom firmware on your device, because this is sometimes a blocking
part of the flashing process.

A firmware format is most of the time composed of the following fields:

<span class="k">\begin</span><span class="nb">{</span>itemize<span class="nb">}</span>
<span class="k">\item</span> header, containing a firmware version and additional fields: Vendor, Hardware version ...
<span class="k">\item</span> CRC32 checksum on either the whole file or just part of it
<span class="k">\item</span> Binary and/or compressed kernel image
<span class="k">\item</span> Binary and/or compressed root filesystem image
<span class="k">\item</span> potential garbage
<span class="k">\end</span><span class="nb">{</span>itemize<span class="nb">}</span>

Once you have figured out how the firmware format is partitioned, you will have 
to write your own tool that produces valid firmware binaries. One thing to be very
careful here is the endianness of either the machine that produces the binary 
firmware and the device that will be flashed using this binary firmware.

<span class="k">\subsubsection</span><span class="nb">{</span>Writing a flash map driver<span class="nb">}</span>

The flash map driver has an important role in making your custom firmware work 
because it is responsible of mapping the correct flash regions and associated 
rights to specific parts of the system such as: bootloader, kernel, user filesystem.

Writing your own flash map driver is not really a hard task once you know how your
firmware image and flash is structured. You will find below a commented example
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 <span class="k">\</span>
<span class="k">\textbf</span><span class="nb">{</span>linux/drivers/mtd/maps/Kconfig<span class="nb">}</span>:

<span class="k">\begin</span><span class="nb">{</span>verbatim<span class="nb">}</span>
config MTD<span class="nb">_</span>DEVICE<span class="nb">_</span>FLASH
        tristate &quot;Device Flash device&quot;
        depends on ARCHITECTURE <span class="nb">&amp;&amp;</span> DEVICE
        help
         Flash memory access on DEVICE boards. Currently only works with
         Bootloader Foo and Bootloader Bar.
<span class="k">\end</span><span class="nb">{</span>verbatim<span class="nb">}</span>

Then add your source file to the <span class="k">\textbf</span><span class="nb">{</span>linux/drivers/mtd/maps/Makefile<span class="nb">}</span>, so 
that it will be compiled along with the kernel.

<span class="k">\begin</span><span class="nb">{</span>verbatim<span class="nb">}</span>
obj-<span class="k">\$</span>(CONFIG<span class="nb">_</span>MTD<span class="nb">_</span>DEVICE<span class="nb">_</span>FLASH)      += device-flash.o
<span class="k">\end</span><span class="nb">{</span>verbatim<span class="nb">}</span>

You can then write the kernel driver itself, by creating a 
<span class="k">\textbf</span><span class="nb">{</span>linux/drivers/mtd/maps/device-flash.c<span class="nb">}</span> C source file.

<span class="k">\begin</span><span class="nb">{</span>verbatim<span class="nb">}</span>
// Includes that are required for the flash map driver to know of the prototypes:
#include &lt;asm/io.h&gt;
#include &lt;linux/init.h&gt;
#include &lt;linux/kernel.h&gt;
#include &lt;linux/mtd/map.h&gt;
#include &lt;linux/mtd/mtd.h&gt;
#include &lt;linux/mtd/partitions.h&gt;
#include &lt;linux/vmalloc.h&gt;

// Put some flash map definitions here:
#define WINDOW<span class="nb">_</span>ADDR 0x1FC00000         /* Real address of the flash */
#define WINDOW<span class="nb">_</span>SIZE 0x400000                /* Size of flash */
#define BUSWIDTH 2                                   /* Buswidth */

static void <span class="nb">__</span>exit device<span class="nb">_</span>mtd<span class="nb">_</span>cleanup(void);

static struct mtd<span class="nb">_</span>info *device<span class="nb">_</span>mtd<span class="nb">_</span>info;

static struct map<span class="nb">_</span>info devicd<span class="nb">_</span>map = <span class="nb">{</span>
       .name = &quot;device&quot;,
       .size = WINDOW<span class="nb">_</span>SIZE,
       .bankwidth = BUSWIDTH,
       .phys = WINDOW<span class="nb">_</span>ADDR,
<span class="nb">}</span>;

static int <span class="nb">__</span>init device<span class="nb">_</span>mtd<span class="nb">_</span>init(void)
<span class="nb">{</span>
	  // Display that we found a flash map device 
       printk(&quot;device: 0x<span class="k">\%</span>08x at 0x<span class="k">\%</span>08x<span class="k">\n</span>&quot;, WINDOW<span class="nb">_</span>SIZE, WINDOW<span class="nb">_</span>ADDR);
	   // Remap the device address to a kernel address
       device<span class="nb">_</span>map.virt = ioremap(WINDOW<span class="nb">_</span>ADDR, WINDOW<span class="nb">_</span>SIZE);

       // If impossible to remap, exit with the EIO error
       if (!device<span class="nb">_</span>map.virt) <span class="nb">{</span>
               printk(&quot;device: Failed to ioremap<span class="k">\n</span>&quot;);
               return -EIO;
       <span class="nb">}</span>

	   // Initialize the device map
       simple<span class="nb">_</span>map<span class="nb">_</span>init(<span class="nb">&amp;</span>device<span class="nb">_</span>map);

	   /* MTD informations are closely linked to the flash map device
	       you might also use &quot;jedec<span class="nb">_</span>probe&quot; &quot;amd<span class="nb">_</span>probe&quot; or &quot;intel<span class="nb">_</span>probe&quot; */
       device<span class="nb">_</span>mtd<span class="nb">_</span>info = do<span class="nb">_</span>map<span class="nb">_</span>probe(&quot;cfi<span class="nb">_</span>probe&quot;, <span class="nb">&amp;</span>device<span class="nb">_</span>map);

 		if (device<span class="nb">_</span>mtd<span class="nb">_</span>info) <span class="nb">{</span>
               device<span class="nb">_</span>mtd<span class="nb">_</span>info-&gt;owner = THIS<span class="nb">_</span>MODULE;

				int parsed<span class="nb">_</span>nr<span class="nb">_</span>parts = 0;

						// We try here to use the partition schema provided by the bootloader specific code
                       if (parsed<span class="nb">_</span>nr<span class="nb">_</span>parts == 0) <span class="nb">{</span>
                               int ret = parse<span class="nb">_</span>bootloader<span class="nb">_</span>partitions(device<span class="nb">_</span>mtd<span class="nb">_</span>info, <span class="nb">&amp;</span>parsed<span class="nb">_</span>parts, 0);
                               if (ret &gt; 0) <span class="nb">{</span>
                                       part<span class="nb">_</span>type = &quot;BootLoader&quot;;
                                       parsed<span class="nb">_</span>nr<span class="nb">_</span>parts = ret;
                               <span class="nb">}</span>
                       <span class="nb">}</span>

                       add<span class="nb">_</span>mtd<span class="nb">_</span>partitions(devicd<span class="nb">_</span>mtd<span class="nb">_</span>info, parsed<span class="nb">_</span>parts, parsed<span class="nb">_</span>nr<span class="nb">_</span>parts);

                       return 0;
               <span class="nb">}</span>
       iounmap(device<span class="nb">_</span>map.virt);

       return -ENXIO;
<span class="nb">}</span>

// This function will make the driver clean up the MTD device mapping
static void <span class="nb">__</span>exit device<span class="nb">_</span>mtd<span class="nb">_</span>cleanup(void)
<span class="nb">{</span>
	  // If we found a MTD device before
       if (device<span class="nb">_</span>mtd<span class="nb">_</span>info) <span class="nb">{</span>
			   // Delete every partitions
               del<span class="nb">_</span>mtd<span class="nb">_</span>partitions(device<span class="nb">_</span>mtd<span class="nb">_</span>info);
			   // Delete the associated map
               map<span class="nb">_</span>destroy(device<span class="nb">_</span>mtd<span class="nb">_</span>info);
       <span class="nb">}</span>
	
		// If the virtual address is already in use
       if (device<span class="nb">_</span>map.virt) <span class="nb">{</span>
					// Unmap the physical address to a kernel space address
               iounmap(device<span class="nb">_</span>map.virt);
				// Reset the structure field
              device<span class="nb">_</span>map.virt = 0;
       <span class="nb">}</span>
<span class="nb">}</span>


// Macros that indicate which function is called on loading/unloading the module
module<span class="nb">_</span>init(device<span class="nb">_</span>mtd<span class="nb">_</span>init);
module<span class="nb">_</span>exit(device<span class="nb">_</span>mtd<span class="nb">_</span>cleanup);


// Macros defining license and author, parameters can be defined here too.
MODULE<span class="nb">_</span>LICENSE(&quot;GPL&quot;);
MODULE<span class="nb">_</span>AUTHOR(&quot;Me, myself and I &lt;memyselfandi@domain.tld&quot;);
<span class="k">\end</span><span class="nb">{</span>verbatim<span class="nb">}</span>

<span class="k">\subsection</span><span class="nb">{</span>Adding your target in OpenWrt<span class="nb">}</span>

Once you spotted the key changes that were made to the Linux kernel
to support your target, you will want to create a target in OpenWrt
for your hardware. This can be useful to benefit from the toolchain
that OpenWrt builds as well as the resulting user-space and kernel
configuration options.

Provided that your target is already known to OpenWrt, it will be
as simple as creating a <span class="k">\texttt</span><span class="nb">{</span>target/linux/board<span class="nb">}</span> directory
where you will be creating the following directories and files.

Here for example, is a <span class="k">\texttt</span><span class="nb">{</span>target/linux/board/Makefile<span class="nb">}</span>:

<span class="k">\begin</span><span class="nb">{</span>Verbatim<span class="nb">}</span>[frame=single,numbers=left]
#
# Copyright (C) 2009 OpenWrt.org
#
# This is free software, licensed under the GNU General Public License v2.
# See /LICENSE for more information.
#
include <span class="s">$</span><span class="o">(</span><span class="nb">TOPDIR</span><span class="o">)/</span><span class="nb">rules.mk</span>

<span class="nb">ARCH:</span><span class="o">=</span><span class="nb">mips</span>
<span class="nb">BOARD:</span><span class="o">=</span><span class="nb">board</span>
<span class="nb">BOARDNAME:</span><span class="o">=</span><span class="nb">Eval board</span>
<span class="nb">FEATURES:</span><span class="o">=</span><span class="nb">squashfs jffs</span><span class="m">2</span><span class="nb"> pci usb</span>

<span class="nb">LINUX_VERSION:</span><span class="o">=</span><span class="m">2</span><span class="nb">.</span><span class="m">6</span><span class="nb">.</span><span class="m">27</span><span class="nb">.</span><span class="m">10</span><span class="nb"></span>

<span class="nb">include </span><span class="s">$</span>(INCLUDE<span class="nb">_</span>DIR)/target.mk

DEFAULT<span class="nb">_</span>PACKAGES += hostapd-mini

define Target/Description
        Build firmware images for Evaluation board
endef

<span class="s">$</span><span class="o">(</span><span class="nb">eval </span><span class="s">$</span>(call BuildTarget))
<span class="k">\end</span><span class="nb">{</span>Verbatim<span class="nb">}</span>

<span class="k">\begin</span><span class="nb">{</span>itemize<span class="nb">}</span>
    <span class="k">\item</span> <span class="k">\texttt</span><span class="nb">{</span>ARCH<span class="nb">}</span> <span class="k">\\</span>
        The name of the architecture known by Linux and uClibc
    <span class="k">\item</span> <span class="k">\texttt</span><span class="nb">{</span>BOARD<span class="nb">}</span> <span class="k">\\</span>
        The name of your board that will be used as a package and build directory identifier
    <span class="k">\item</span> <span class="k">\texttt</span><span class="nb">{</span>BOARDNAME<span class="nb">}</span> <span class="k">\\</span>
        Expanded name that will appear in menuconfig
    <span class="k">\item</span> <span class="k">\texttt</span><span class="nb">{</span>FEATURES<span class="nb">}</span> <span class="k">\\</span>
        Set of features to build filesystem images, USB, PCI, VIDEO kernel support
    <span class="k">\item</span> <span class="k">\texttt</span><span class="nb">{</span>LINUX<span class="k">\_</span>VERSION<span class="nb">}</span> <span class="k">\\</span>
        Linux kernel version to use for this target
    <span class="k">\item</span> <span class="k">\texttt</span><span class="nb">{</span>DEFAULT<span class="k">\_</span>PACKAGES<span class="nb">}</span> <span class="k">\\</span>
        Set of packages to be built by default
<span class="k">\end</span><span class="nb">{</span>itemize<span class="nb">}</span>

A partial kernel configuration which is either named <span class="k">\texttt</span><span class="nb">{</span>config-default<span class="nb">}</span> or which matches the kernel version <span class="k">\texttt</span><span class="nb">{</span>config-2.6.x<span class="nb">}</span> should be present in <span class="k">\texttt</span><span class="nb">{</span>target/linux/board/<span class="nb">}</span>.
This kernel configuration will only contain the relevant symbols to support your target and can be changed using <span class="k">\texttt</span><span class="nb">{</span>make kernel<span class="k">\_</span>menuconfig<span class="nb">}</span>.

To patch the kernel sources with the patches required to support your hardware, you will have to drop them in <span class="k">\texttt</span><span class="nb">{</span>patches<span class="nb">}</span> or in <span class="k">\texttt</span><span class="nb">{</span>patches-2.6.x<span class="nb">}</span> if there are specific
changes between kernel versions. Additionnaly, if you want to avoid creating a patch that will create files, you can put those files into <span class="k">\texttt</span><span class="nb">{</span>files<span class="nb">}</span> or <span class="k">\texttt</span><span class="nb">{</span>files-2.6.x<span class="nb">}</span>
with the same directory structure that the kernel uses (e.g: drivers/mtd/maps, arch/mips ..).

The build system will require you to create a <span class="k">\texttt</span><span class="nb">{</span>target/linux/board/image/Makefile<span class="nb">}</span>:

<span class="k">\begin</span><span class="nb">{</span>Verbatim<span class="nb">}</span>[frame=single,numbers=left]
#
# Copyright (C) 2009 OpenWrt.org
#
# This is free software, licensed under the GNU General Public License v2.
# See /LICENSE for more information.
#
include <span class="s">$</span><span class="o">(</span><span class="nb">TOPDIR</span><span class="o">)/</span><span class="nb">rules.mk</span>
<span class="nb">include </span><span class="s">$</span>(INCLUDE<span class="nb">_</span>DIR)/image.mk

define Image/BuildKernel
        cp <span class="s">$</span><span class="o">(</span><span class="nb">KDIR</span><span class="o">)/</span><span class="nb">vmlinux.elf </span><span class="s">$</span>(BIN<span class="nb">_</span>DIR)/openwrt-<span class="s">$</span><span class="o">(</span><span class="nb">BOARD</span><span class="o">)-</span><span class="nb">vmlinux.elf</span>
<span class="nb">        gzip </span><span class="o">-</span><span class="m">9</span><span class="nb"> </span><span class="o">-</span><span class="nb">c </span><span class="s">$</span>(KDIR)/vmlinux &gt; <span class="s">$</span><span class="o">(</span><span class="nb">KDIR</span><span class="o">)/</span><span class="nb">vmlinux.bin.gz</span>
<span class="nb">        </span><span class="s">$</span>(STAGING<span class="nb">_</span>DIR<span class="nb">_</span>HOST)/bin/lzma e <span class="s">$</span><span class="o">(</span><span class="nb">KDIR</span><span class="o">)/</span><span class="nb">vmlinux </span><span class="s">$</span>(KDIR)/vmlinux.bin.l7
        dd if=<span class="s">$</span><span class="o">(</span><span class="nb">KDIR</span><span class="o">)/</span><span class="nb">vmlinux.bin.l</span><span class="m">7</span><span class="nb"> of</span><span class="o">=</span><span class="s">$</span>(BIN<span class="nb">_</span>DIR)/openwrt-<span class="s">$</span><span class="o">(</span><span class="nb">BOARD</span><span class="o">)-</span><span class="nb">vmlinux.lzma bs</span><span class="o">=</span><span class="m">65536</span><span class="nb"> conv</span><span class="o">=</span><span class="nb">sync</span>
<span class="nb">        dd if</span><span class="o">=</span><span class="s">$</span>(KDIR)/vmlinux.bin.gz of=<span class="s">$</span><span class="o">(</span><span class="nb">BIN_DIR</span><span class="o">)/</span><span class="nb">openwrt</span><span class="o">-</span><span class="s">$</span>(BOARD)-vmlinux.gz bs=65536 conv=sync
endef

define Image/Build/squashfs
    <span class="s">$</span><span class="o">(</span><span class="nb">call prepare_generic_squashfs,</span><span class="s">$</span>(KDIR)/root.squashfs)
endef

define Image/Build
        <span class="s">$</span><span class="o">(</span><span class="nb">call Image</span><span class="o">/</span><span class="nb">Build</span><span class="o">/</span><span class="s">$</span>(1))
        dd if=<span class="s">$</span><span class="o">(</span><span class="nb">KDIR</span><span class="o">)/</span><span class="nb">root.</span><span class="s">$</span>(1) of=<span class="s">$</span><span class="o">(</span><span class="nb">BIN_DIR</span><span class="o">)/</span><span class="nb">openwrt</span><span class="o">-</span><span class="s">$</span>(BOARD)-root.<span class="s">$</span><span class="o">(</span><span class="m">1</span><span class="o">)</span><span class="nb"> bs</span><span class="o">=</span><span class="m">128</span><span class="nb">k conv</span><span class="o">=</span><span class="nb">sync</span>

<span class="nb">        </span><span class="o">-</span><span class="s">$</span>(STAGING<span class="nb">_</span>DIR<span class="nb">_</span>HOST)/bin/mkfwimage <span class="k">\</span>
                -B XS2 -v XS2.ar2316.OpenWrt <span class="k">\</span>
                -k <span class="s">$</span><span class="o">(</span><span class="nb">BIN_DIR</span><span class="o">)/</span><span class="nb">openwrt</span><span class="o">-</span><span class="s">$</span>(BOARD)-vmlinux.lzma <span class="k">\</span>
                -r <span class="s">$</span><span class="o">(</span><span class="nb">BIN_DIR</span><span class="o">)/</span><span class="nb">openwrt</span><span class="o">-</span><span class="s">$</span>(BOARD)-root.<span class="s">$</span><span class="o">(</span><span class="m">1</span><span class="o">)</span><span class="nb"> </span><span class="err">\</span><span class="nb"></span>
<span class="nb">                </span><span class="o">-</span><span class="nb">o </span><span class="s">$</span>(BIN<span class="nb">_</span>DIR)/openwrt-<span class="s">$</span><span class="o">(</span><span class="nb">BOARD</span><span class="o">)-</span><span class="nb">ubnt</span><span class="m">2</span><span class="o">-</span><span class="s">$</span>(1).bin
endef

<span class="s">$</span><span class="o">(</span><span class="nb">eval </span><span class="s">$</span>(call BuildImage))

<span class="k">\end</span><span class="nb">{</span>Verbatim<span class="nb">}</span>

<span class="k">\begin</span><span class="nb">{</span>itemize<span class="nb">}</span>
    <span class="k">\item</span> <span class="k">\texttt</span><span class="nb">{</span>Image/BuildKernel<span class="nb">}</span> <span class="k">\\</span>
        This template defines changes to be made to the ELF kernel file
    <span class="k">\item</span> <span class="k">\texttt</span><span class="nb">{</span>Image/Build<span class="nb">}</span> <span class="k">\\</span>
	This template defines the final changes to apply to the rootfs and kernel, either combined or separated
	firmware creation tools can be called here as well.
<span class="k">\end</span><span class="nb">{</span>itemize<span class="nb">}</span>
</pre></div>
</code></pre></td></tr></table>
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