12. Rolling your own - Cross Compiling a Kernel for the 5MX

It is usually not necessary to compile your own kernel. Binaries are available and so far they have been regularly updated as the kernel development proceeds. Should you want to dabble in, e.g., kernel development, however, here is the basic information on how to compile a kernel.

12.1 Prerequisites

There are four things you will need to gather together to compile a kernel for the 5MX:

1. the ARM cross compiler (x MB)
2. the kernel sources (about 30 MB)
3. Russel King's generic ARM kernel patch (a few hundred KB), and
4. Tony L.'s Psion 5MX kernel patch (100 KB)

The sections below discuss how to go about obtaining these, and what to do with then once you've got them. The ARM cross compiler can also be used to compile other programs that will run on the 5MX.

12.2 The Cross Compilation Environment

Your own custom kernel can be created using the cross compilation environment. "Cross compilation" means using an i386 desktop computer to compile code that will run on the ARM computer. The cross compiler will also allow you to compile your own applications for the ARM system. To set it up, go to http://www.aleph1.co.uk/armlinux/book/x1768.html for some (now slightly out of date but still functional) info on available toolchains. I like the emdebian one best as the install is painless and operation is seamless.

12.3 Compiling a Kernel

Using the cross compilation environment described above, you can create your own kernel. To compile a custom kernel, you will need to download a kernel tarball - see http://www.aleph1.co.uk/armlinux/book/kernelcompile.html for some generic info on kernel building. You will need the base source code for the kernel, AND the ARM patch (rmk's), e.g., patch-2.4.18-rmk6.gz. The kernel source code can be obtained HERE, and the ARM patch can be obtained HERE.

In addition, get the 5MX patch for the kernel from http://linux-7110.sourceforge.net/files/Kernels/5mx_and_Revo/ - look for a file like: "linux-2.4.18-rmk6-5mx4.patch.gz" (this one would be for the 2.4.18 kernel, of course). Be sure that the kernel source, the ARM patch, and the 5MX patch all have the same version number - version 2.4.18 is used as an example here.

Assuming that you have downloaded these and copied them to a directory like $HOME/armkernel, execute the following commands:
cd $HOME/armkernel
gunzip linux-2.4.18.tar.gz
tar xvf linux-2.4.18.tar
cd linux
patch -p1 < patch-2.4.18-rmk6
patch -p1 < linux-2.4.18-rmk6-5mx4.patch


These commands will patch the Linux kernel for use with the Psion Series 5MX.

You must now configure and compile the kernel. To configure it, execute:
make psion_5mx_ericsson_mc218_config

[uk, us, or de keyboard types are now set by kernel configuration]

make oldconfig
then one of:
make xconfig or make menuconfig or make config
(in this context the latter is preferred as it only asks you about the new options and you just take the defaults for them all - the menu stuff just makes it more conplicated). You'll need to set your keyboard type - uk, us, or de (and a patch exists for the nordic keyboard).

Once you've prepared your source, make sure your linux/Makefile has
CROSS_COMPILE = arm-linux-
at about line 24; this should occur by default..

When you have done this, execute these commands to make the kernel:
make dep
make Image [NOT bzImage or zImage - kernels must be uncompressed.]

This command will create a kernel image named "Image" in arch/arm/boot/ . This kernel image should then work as the kernel image to be loaded by ARLO.