README

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Raspberry PI Most Stupid Kernel Ever 
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A simple kernel from scratch is something that I've always wanted to do.
This not pretend to be something big but big enough to undertand how a lot of stuff really works.
Because I have a Raspberry Pi model B this is the target platform.

= WHAT IS AN WHAT IS NOT INCLUDED =

There are different stuff currently supported in the kernel. These are:

* Driver for uart
* General GPIO driver code.
* Boot led driver over gpio.
* Interrupt support. It allows to define own interrupt handlers.
* Global raspberri pi timer.
* Arm-side timer with interrupts.
* Minimal processes support. All of them running in the same address space.
* Minimal semaphores implementation.
* Caches and virtual memory is not supported yet.

= HOW TO COMPILE =

You need to install arm crosscompiler arm-none-eabi-gcc package to be able to compile the sources.

$ mkdir build
$ cd build
$ cmake -DCMAKE_TOOLCHAIN_FILE=/absolute_path_to/rpi-mske/toolchain/toolchain-arm-none-eabi-rpi.cmake ..
$ make

Binary kernel.img file should be created.

= HOW TO DEPLOY IN THE TARGET =

There are two methods to be able to deploy built kernel in the target.

== Manually ==

Generated kernel.img is the image you have to use as your kernel image.

Create a sdcard with a fat partition and add the files included in sd_boot directory.
Add kernel.img to the partition too.

== Create_sdcard script ==

There is a script in tools directory that allows you to generate a bootable sdcard. Invoke it without params shows script's help.

$ sudo ./create_sdcard.sh 

Usage: ./create_sdcard.sh -k <kernel_img_file> -d <sdcard_device>

So, if your device is /dev/sdb the following command will generate the bootable sdcard.

$ ./create_sdcard.sh -k ../build/kernel.img -d /dev/sdb

Boot your pi connected with ftdi cable to gpio and use minicom or other terminal program to view boot process.

Enjoy!