Adding hardware support to Buildroot

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1 Adding hardware support to Buildroot Pierre Ficheux CTO Open Wide / OS4I 08/07/2010 1

2 Several ways to get a distribution Using commercial product (Wind River, MV, ) => / $$$ Adapting standard GNU/Linux distribution :( Hardware support limitation Large footprint Creating «from scratch» Good knowledge necessary Not industrial: dependencies, updates, etc. Using a generation tool :-) Buildroot, OpenEmbedded, LTIB,... 2

3 Generation tool principle An software engine generates distribution from adapted sources by applying patches Sources are not provides: only patches + root-fs skeleton Handle dependencies :) Can produce the «GNU Toolchain» (gcc,...) Can produce distribution, several images : Bootloader image (u-boot.bin) Linux kernel (zimage, uimage) Root-fs image: EXT2, JFFS2, CRAMFS, TAR, CPIO,... 3

4 Some famous tools OpenEmbedded Engine written in Python (BitBake) Very powerful but complicated Based on configuration files (no GUI) LTIB Used by Freescale Looks like Buildroot but old fashioned Buildroot First a demonstrator for uclibc Since 2009, a powerful, well maintained tool! 4

5 About Buildroot Linked with uclibc (micro-c-libc) : lightweight Libc (about 5 times smaller / Glibc) Initial goal: producing test images for uclibc Engine based on Makefile(s) and shell-scripts :-) Based on Busybox Use Kconfig language (just like kernel configurator) in Config.in files for GUI Can produce toolchain (uclibc based) or use external toolchain No official release before 2009 :( 5

6 Buildroot today Since 2009, managed by Peter Korsgaard and Thomas Petazzoni Official realease every 3 months: ,..., , , Switched to Git :) More documentation More packages, with extended.mk since 2010 Supports x86, ARM, PowerPC, SH4, Direct supports for some boards: Atmel,... It s simple to add board support, if you are fluent in Makefile and Kconfig! 6

7 Using Buildroot in a nutshell Get it from Extract archive Configure with make menuconfig Compile with make Results is in output/images Bootloader image Linux kernel Root-filesystem image(s) Needs a fast connection for downloading sources (or use make sources first then work off-line) 7

8 Configuring Buildroot Target Architecture + Variant : arm then arm920t Target options: trivial if in Preset Devices Toolchain: internal (uclibc) or external (Glibc, Eglibc, ) => could be tricky Packages => what to add to root-filesystem, at least Busybox Target filesystems: JFFS2, CRAMFS, SQUASHFS (flash), TAR (NFS Root) Kernel and Bootloaders (disabled by default) Configuration saved in.config file 8

9 Advanced configuration, stage 1 In case of supported board, just type make myboard_config Once.config is done, just copy it to configs/myboard_config, but... Some configuration are not accessible by GUI Cool, it s fine not to give access to everything to GUI lovers It s nice to have board definition in Preset Devices Fine to be able to tune the configuration (in case of similar boards from same maker) Smart for marketing guys :) 9

10 What can you do with Advanced configuration, stage 2? Quite everything! Target specific skeleton for rootfs => TARGET_SKELETON Target specific /dev content => TARGET_DEVICE_TABLE Customized kernel patches + configuration Customized U-Boot sources + configuration Handle a set a boards with common configuration + one by one tuning (i.e. : adding /dev/foo to board A and /dev/bar to board B) 10

11 What do you need to know? Read first! Makefile Good knowledge Config.in => Kconfig language Good knowledge Shell script Basic knowledge grep -R BR2_ * Very good knowledge :) Cut/paste! Very good knowledge ;-) 11

12 Example, example!! Want to add boards model A and model B from Board Maker Inc. company (BMI) Board Maker Inc. provides only support for a specific old version of kernel, assuming Model A and Model B use same kernel patch BUT different kernel configuration Model A and Model B use same U-Boot version BUT different patches Each board has specific entries in /dev (defined by device_table.txt) Each board has specific Busybox configuration (why not?) 12

13 Step 1, adding board(s) directory Several ways to do the job, here is one! First create a target/devices/bmi directory with ModelA and ModelB and kernel-patches subdirs Copy Board Maker specific patch file to kernelpatches with.patch extension As boards use same kernel patch, you should put it at BMI level (save space) Add the following to target/device/config.in source "target/device/bmi/config.in" 13

14 Step 2: creating Config.in for BMI Create target/device/bmi/config.in Define a new variable BR2_TARGET_BMI BMI => ARM + ARM920 + OABI menuconfig BR2_TARGET_BMI depends on (BR2_arm && BR2_arm920t && BR2_ARM_OABI) bool "Support for Board Maker Inc. boards" help Support for Board Maker Inc. boards 14

15 Step 3: adding definition for boards if BR2_TARGET_BMI config BR2_TARGET_BMI_MODEL_A bool "Support for BMI Model A" help Support for BMI Model A config BR2_TARGET_BMI_MODEL_B bool "Support for BMI Model B" help Support for BMI Model A 15

16 Step 4: Adding boards names if BR2_TARGET_BMI_MODEL_A config BR2_BOARD_NAME string default "ModelA" <--- force value endif if BR2_TARGET_BMI_MODEL_B config BR2_BOARD_NAME string default "ModelB" endif 16

17 Step 5: Generic parameters 1/2 Depend on board names config BR2_BOARD_PATH string default "target/device/bmi/$(br2_board_name)" # BMI uses specific kernel version config BR2_KERNEL_ARCH_PATCH_VERSION string depends on BR2_KERNEL_ARCH_PATCH_ENABLED default " " 17

18 Step 6: Generic parameters 2/2 Kernel patch path, same U-Boot version End of Config.in :) config BR2_KERNEL_ARCH_PATCH_DIR string default "target/device/bmi/kernel-patches-$ (BR2_KERNEL_ARCH_PATCH_VERSION)" config BR2_UBOOT_VERSION string default "1.1.6" endif 18

19 Step 7: Makefile.in Simpler: defines specific variables at compilation time Use qstrip macro to get basename BOARD_NAME:=$(call qstrip,$(br2_board_name)) BOARD_PATH:=$(call qstrip,$(br2_board_path)) TARGET_DEVICE_TABLE=$(BOARD_PATH)/device_table.txt BR2_PACKAGE_BUSYBOX_CONFIG=$(BOARD_PATH)/busybox.config 19

20 Step 8: ModelA/ModelB content ModelA busybox.config ModelA-linux config device_table.txt u-boot patch ModelB busybox.config ModelB-linux config device_table.txt u-boot patch 20

21 Step 9: Test new GUI New Board Maker Inc. entries should appear in Target options / Preset Devices menu if you set correct dependencies We could carry on with configuration files but a bit complicated => let GUI help us for each board : Kernel U-Boot System banner System name Console device (UART) Toolchain... 21

22 Step 10: U-Boot In Bootloaders menu Das U-Boot Boot Monitor Set board name to U-Boot board name (not BR board name!) => bmi_a, bmi_b BR will do make myboard_config to build U- boot Set custom patch to $(BR2_BOARD_PATH)/uboot patch U-Boot Version is useless as BR2_UBOOT_VERSION was set in Config.in 22

23 Step 10 screen 23

24 For Kernel type, select linux (Advanced configuration) In Linux Kernel Version select Linux <custom> version Step 11: Kernel Enter to Linux Tarball Version AND Linux Version In Patches menu, set Add ARCH specific patch In Linux Kernel configuration menu, select.config file option which should depend on BR2_BOARD_PATH and BR2_BOARD_NAME Set kernel binary format to uimage as we use U- Boot 24

25 Step 11, screen 1 25

26 Step 11, screen 2 26

27 Step 11, screen 3 27

28 Step 12: finish configuration Set any other parameter, just like the first test: packages, toolchain, rootfs images in Target filesystems options menu, Save your configuration for each board! Copy each.config to configs/bmi_modelx_defconfig file (X= A then B) That s it! 28

29 Providing BR support for BMI boards As a board maker you just have to : Tell to customer to get standard BR => you don t maintain a specific tool + BR is famous now Simply provide a patch to BR in order to add your products to Preset Devices list Patch will include everything added to standard BR As a customer you just have to : Get standard BR + apply board maker patch Type make bmi_modela_defconfig (or B) then type make Flash output/images/* files to the board :) 29

30 Why using Buildroot Stable, maintained by embedded Linux experts For customers and board makers: ONE Interface for ALL boards Graphical GUI with make xconfig Light and fast: get everything including toolchain in 20/25 mn with standard Core 2 Duo PC, several hours for OE Should become (if not already) a standard in embedded Linux world 30

31 Questions? 31

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