1.2. barebox

1.2.1. Getting barebox

barebox is released on a monthly basis. The version numbers use the format YYYY.MM.N, so 2014.06.0 is the monthly release for June 2014. Stable releases are done as needed to fix critical problems and are indicated by incrementing the suffix (for example 2014.06.1).

All releases can be downloaded from:

https://www.barebox.org/download/

Development versions of barebox are accessible via Git. A local repository clone can be checked out as follows:

$ git clone git://git.pengutronix.de/git/barebox.git
Cloning into 'barebox'...
remote: Counting objects: 113356, done.
remote: Compressing objects: 100% (25177/25177), done.
remote: Total 113356 (delta 87910), reused 111155 (delta 85935)
Receiving objects: 100% (113356/113356), 33.13 MiB | 183.00 KiB/s, done.
Resolving deltas: 100% (87910/87910), done.
Checking connectivity... done.
Checking out files: 100% (5651/5651), done.

By default, the master branch is checked out. If you want to develop for barebox, this is the right branch to send patches against.

If you want to see which patches are already selected for the next release, you can look at the next branch:

$ git checkout -b next origin/remotes/next

A web interface to the repository is available at https://git.pengutronix.de/cgit/barebox

1.2.2. Configuration

barebox uses Kconfig from the Linux kernel as a configuration tool, where all configuration is done via the make command. Before running it you have to specify your architecture with the ARCH environment variable and the cross compiler with the CROSS_COMPILE environment variable. Currently, ARCH must be one of:

  • arm
  • blackfin
  • mips
  • nios2
  • openrisc
  • ppc
  • riscv
  • sandbox
  • x86

CROSS_COMPILE should be the prefix of your cross compiler. This can either contain the full path or, if the cross compiler binary is in your $PATH, just the prefix.

Either export ARCH and CROSS_COMPILE once before working on barebox:

export ARCH=arm
export CROSS_COMPILE=/path/to/arm-cortexa8-linux-gnueabihf-
make ...

or add them to each invocation of the make command:

ARCH=arm CROSS_COMPILE=/path/to/arm-cortexa8-linux-gnueabihf- make ...

For readability, ARCH/CROSS_COMPILE are skipped from the following examples.

1.2.2.1. Configuring for a board

All configuration files can be found under the arch/${ARCH}/configs/ directory. For an overview of possible Make targets for your architecture, type:

make help

Your output from make help will be based on the architecture you’ve selected via the ARCH variable. So if, for example, you had selected:

export ARCH=mips

your help output would represent all of the generic (architecture-independent) targets, followed by the MIPS-specific ones:

make [ARCH=mips] help
...
... list of generic targets ...
...
Architecture specific targets (mips):
  No architecture specific help defined for mips

  ath79_defconfig          - Build for ath79
  bcm47xx_defconfig        - Build for bcm47xx
  gxemul-malta_defconfig   - Build for gxemul-malta
  loongson-ls1b_defconfig  - Build for loongson-ls1b
  qemu-malta_defconfig     - Build for qemu-malta
  xburst_defconfig         - Build for xburst

barebox supports building for multiple boards with a single config. If you can’t find your board in the list, it may be supported by one of the multi-board configs. As an example, this is the case for tegra_v7_defconfig and imx_v7_defconfig. Select your config with make <yourboard>_defconfig:

make imx_v7_defconfig

The configuration can be further customized with one of the configuration frontends with the most popular being menuconfig:

make menuconfig

barebox uses the same configuration and build system as Linux (Kconfig, Kbuild), so you can use all the kernel config targets you already know, e.g. make xconfig, make allyesconfig etc.

1.2.2.2. Configuring and compiling “out-of-tree”

Before going any further, it’s worth knowing how you can do all your barebox configuration and compilation “out of tree”; that is, how you can keep your source directory pristine and have all output from the various make commands generated in a separate build directory.

Once you check out your barebox source directory, and before you do any configuration or building, set the environment variable KBUILD_OUTPUT to point to your intended output directory, as in:

export KBUILD_OUTPUT=.../my_barebox_build_directory

From that point on, all of the make commands you run in your source directory will generate their output in your specified output directory. Not only does this keep your source directory clean, but it allows several developers to share the same source directory while doing all their own configuration and building in their own individual build directories.

Note

To do out-of-tree builds, your source tree must be absolutely clean of all generated artifacts from previous configurations and builds. In other words, if you had earlier done any configuration or building in that source tree that dumped its results into the same source tree directory, you need to do the equivalent of a make distclean before using that source directory for any out-of-tree builds.

1.2.3. Compilation

After barebox has been configured it can be compiled simply with:

make

The resulting binary varies depending on the board barebox is compiled for. Without Multi Image Support support the barebox-flash-image link will point to the binary for flashing/uploading to the board. With Multi Image Support support the compilation process will finish with a list of images built under images/:

images built:
barebox-freescale-imx51-babbage.img
barebox-genesi-efikasb.img
barebox-freescale-imx53-loco.img
barebox-freescale-imx53-loco-r.img
barebox-freescale-imx53-vmx53.img
barebox-tq-mba53-512mib.img
barebox-tq-mba53-1gib.img
barebox-datamodul-edm-qmx6.img
barebox-guf-santaro.img
barebox-gk802.img

1.2.4. Starting barebox

Bringing barebox to a board for the first time is highly board specific, see your board documentation for initial bringup.

barebox binaries are, where possible, designed to be startable second stage from another bootloader. For example, if you have U-Boot running on your board, you can start barebox with U-Boot’s bootm command:

U-Boot: tftp $load_addr barebox.bin
U-Boot: bootm $load_addr

With barebox already running on your board, this can be used to chainload another barebox. For instance, if you mounted a TFTP server to /mnt/tftp (see TFTP filesystem for how to do that), chainload barebox with:

bootm /mnt/tftp/barebox.bin

At least barebox.bin (with PreBootLoader images (PBL) support enabled arch/$ARCH/pbl/zbarebox.bin) should be startable second stage. The flash binary (barebox-flash-image) may or may not be startable second stage as it may have SoC specific headers which prevent running second stage.

1.2.5. First Steps

This is a typical barebox startup log:

barebox 2014.06.0-00232-g689dc27-dirty #406 Wed Jun 18 00:25:17 CEST 2014


Board: Genesi Efika MX Smartbook
detected i.MX51 revision 3.0
mc13xxx-spi mc13892@00: Found MC13892 ID: 0x0045d0 [Rev: 2.0a]
m25p80 m25p800: sst25vf032b (4096 Kbytes)
ata0: registered /dev/ata0
imx-esdhc 70004000.esdhc: registered as 70004000.esdhc
imx-esdhc 70008000.esdhc: registered as 70008000.esdhc
imx-ipuv3 40000000.ipu: IPUv3EX probed
netconsole: registered as cs2
malloc space: 0xabe00000 -> 0xafdfffff (size 64 MiB)
mmc1: detected SD card version 2.0
mmc1: registered mmc1
barebox-environment environment-sd.7: setting default environment path to /dev/mmc1.barebox-environment
running /env/bin/init...

Hit any key to stop autoboot:  3

barebox@Genesi Efika MX Smartbook:/

Without intervention, barebox will continue booting after 3 seconds. If interrupted by pressing a key, you will find yourself at the shell.

At the shell type help for a list of supported commands. help <command> shows the usage for a particular command. barebox has tab completion which will complete your command. Arguments to commands are also completed depending on the command. If a command expects a file argument only files will be offered as completion. Other commands will only complete devices or devicetree nodes.