RaspberryPi

Intro
=====

To be able to use your RaspberryPi board with the images generated by
Buildroot, you have a prior choice to make, will you use:
    - Volatile rootfs in RAM (The rootfs is an initramfs) or
    - Persistent rootfs on the SDCard

Also, a good source of information is http://elinux.org/R-Pi_Hub

Volatile rootfs
===============

How to build it
---------------

You need to use the rpi_defconfig, to do so:
 * make rpi_defconfig

Then, you need to select the kind of images you want:
 * make menuconfig
 * Select "Filesystem images"
 * Select "initial RAM filesystem linked into linux kernel"

What is generated
-----------------

After building, you should obtain this tree:

    output/images/
    +-- rootfs.tar
    +-- rpi-firmware
    |   +-- bootcode.bin
    |   +-- config.txt
    |   +-- fixup_cd.dat
    |   +-- fixup.dat
    |   +-- start_cd.elf
    |   `-- start.elf
    `-- zImage

Note : rootfs.tar will only be there if you kept "tar the root filesystem"
option selected in "Filesystem images".

Where should the binaries be copied on the SDCard
-------------------------------------------------

Your SDCard must have its first partition using fat32 and marked bootable.

At the root of the partition, the RaspberryPi must find the following files:

 * bootcode.bin
 * config.txt
 * fixup_cd.dat
 * fixup.dat
 * start_cd.elf
 * start.elf
 * zImage

So you should copy the entire content of output/images/rpi-firmware along with
zImage.

Note: You can create any number of partitions you desire, the only requirement
is that the first partition must be using fat32 and bootable.

Persistent rootfs
=================

How to build it
---------------

You only need to use the rpi_defconfig, to do so:
 * make rpi_defconfig

What is generated
-----------------

After building, you should obtain this tree:

    output/images/
    +-- rootfs.tar
    +-- rpi-firmware
    |   +-- bootcode.bin
    |   +-- config.txt
    |   +-- fixup_cd.dat
    |   +-- fixup.dat
    |   +-- start_cd.elf
    |   `-- start.elf
    `-- zImage

Where should the binaries be copied on the SDCard
-------------------------------------------------

Your SDCard must have its first partition using fat32 and marked bootable.
It should also have another partition which will contain your rootfs, it should
be partitioned as ext4.

Boot partition
~~~~~~~~~~~~~~

The first partition will contain everything used to boot the RaspberryPi.
You must copy theses files at the root of partition:

 * bootcode.bin
 * config.txt
 * fixup_cd.dat
 * fixup.dat
 * start_cd.elf
 * start.elf
 * zImage

So you should copy the entire content of output/images/rpi-firmware along with
zImage.

Rootfs partition
~~~~~~~~~~~~~~~~

The second partition will contain your rootfs.
Simply extract (as root!) the contents of the rootfs.tar archive
into this partition.

For example: (Assuming mountpoint is a directory and exist)

 $ sudo mount /dev/sdXY /mnt/mountpoint
 $ sudo tar xf rootfs.tar -C /mnt/mountpoint