add Buildroot chapter, cfg change

book/book.toml

@@ -4,12 +4,14 @@ authors = ["Alexander Kaplan"]
 language = "en"
 multilingual = false
 src = "src"
+
+[output.html]
+cname = "d.eadc0.de"
 default-theme = "dark"
 preferred-dark-theme = "Ayu"
 git-repository-url = "https://github.com/kaplan2539/cindy"
 edit-url-template = "https://github.com/kaplan2539/cindy/edit/<branch>/{path}"
-side-url = "https://d.eadc0.de/cindy"
-cname = "d.eadc0.de"
+site-url = "https://d.eadc0.de/cindy"
 
 [build]
 build-dir = "output"

book/src/SUMMARY.md

@@ -4,3 +4,4 @@
 
 
 - [Warm Up](./warmup.md)
+- [Buildroot](./buildroot.md)

book/src/buildroot.md

@@ -0,0 +1,117 @@
+# Buildroot
+
+In the Warm Up Excercise chapter we've manually installed a cross-compiler,
+downloaded the U-Boot, Linux and Busybox sources, compiled them and created
+a rootfs image.
+In this chapter we are going to use Buildroot to do that for us.
+
+Buildroot is a great tool to generate embedded Linux images.
+It integrates all of the steps mentioned above and makes it really easy to
+add various software packages to the root file system.
+
+We can only give very brief overview of how to use Buildroot for our purposes.
+Luckily, Buildroot comes with
+[detailed documentation](https://buildroot.org/downloads/manual/manual.html)
+ that should cover everything important to know.
+
+Download and unpack the latest "stable" release:
+
+```shell
+wget -c -P download https://buildroot.org/downloads/buildroot-2023.11.tar.gz
+tar xf download/buildroot-2023.11.tar.gz
+```
+
+## Customizing Buildroot for CHIP
+
+We are going to use the 'br2-external' mechanism (c.f. Buildroot documentation
+ [Chapter 9.2](https://buildroot.org/downloads/manual/manual.html#outside-br-custom)
+ ) in order to keep our
+costumizations outside of the official buildroot tree:
+
+```
+mkdir buildroot-external
+export BR2_EXTERNAL="$(realpath buildroot-external)"
+```
+
+Create `buildroot-external/external.desc`:
+
+```
+cat <<EOF >buildroot-external/external.desc
+name: CHIP
+desc: Buildroot configuration for CHIP
+EOF
+```
+
+Create `buildroot-external/external.mk`:
+
+```
+cat <<EOF >buildroot-external/external.mk
+include \$(sort \$(wildcard \$(BR2_EXTERNAL_CHIP_PATH)/package/*/*.mk))
+EOF
+```
+
+Create empty `buildroot-external/Config.in`:
+
+```
+touch buildroot-external/Config.in
+```
+
+Create
+[recommended directory structure](https://buildroot.org/downloads/manual/manual.html#customize-dir-structure):
+
+```shell
+mkdir -p "${BR2_EXTERNAL}"/board/nextthingco/CHIP/{dts,linux,uboot}
+mkdir -p "${BR2_EXTERNAL}"/configs
+```
+
+Create Buildroot configuration for CHIP, for now using the default U-Boot
+`CHIP_defconfig` and Linux `sunxi_defconfig`:
+
+```shell
+cat <<EOF >"${BR2_EXTERNAL}"/configs/nextthingco_chip_defconfig
+BR2_arm=y
+BR2_cortex_a8=y
+BR2_TOOLCHAIN_EXTERNAL=y
+BR2_LINUX_KERNEL=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION=y
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="6.1.68"
+BR2_LINUX_KERNEL_PATCH="${BR2_EXTERNAL_CHIP_PATH}/board/nextthingco/CHIP/linux"
+BR2_LINUX_KERNEL_DEFCONFIG="sunxi"
+BR2_LINUX_KERNEL_DTS_SUPPORT=y
+BR2_LINUX_KERNEL_INTREE_DTS_NAME="sun5i-r8-chip"
+BR2_LINUX_KERNEL_DTB_OVERLAY_SUPPORT=y
+BR2_LINUX_KERNEL_INSTALL_TARGET=y
+BR2_TARGET_ROOTFS_CPIO=y
+BR2_TARGET_ROOTFS_CPIO_GZIP=y
+BR2_TARGET_ROOTFS_CPIO_UIMAGE=y
+BR2_TARGET_UBOOT=y
+BR2_TARGET_UBOOT_BUILD_SYSTEM_KCONFIG=y
+BR2_TARGET_UBOOT_CUSTOM_VERSION=y
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2023.10"
+BR2_TARGET_UBOOT_PATCH="${BR2_EXTERNAL_CHIP_PATH}/board/nextthingco/CHIP/uboot"
+BR2_TARGET_UBOOT_BOARD_DEFCONFIG="CHIP"
+BR2_TARGET_UBOOT_NEEDS_DTC=y
+BR2_TARGET_UBOOT_NEEDS_PYLIBFDT=y
+BR2_TARGET_UBOOT_SPL=y
+BR2_TARGET_UBOOT_SPL_NAME="u-boot-sunxi-with-spl.bin spl/u-boot-spl.bin"
+EOF
+```
+
+Now compile Linux, U-Boot and build a rootfs image using Buildroot:
+
+```shell
+cd buildroot-2023.11
+make nextthingco_chip_defconfig
+make
+```
+
+Buildroot put everything into the `output/images` sub-directory.
+To boot type:
+
+```shell
+cd output/images
+sunxi-fel -v -p uboot u-boot-sunxi-with-spl.bin \
+                write 0x42000000 zImage \
+                write 0x43000000 sun5i-r8-chip.dtb \
+                write 0x43400000 rootfs.cpio.uboot
+```

book/src/warmup.md

@@ -18,13 +18,13 @@ The following has been tested on a `x86_64` computer running Ubuntu 22.04.
 These commands are going to install a cross-compiler toolchain, the
 `sunxi-fel` tool, the `cu` terminal program, and couple of dependencies:
 
-```
+```shell
 sudo bash -c '{{#include ../../setup/install_packages.sh:3:}}'
 ```
 
 Let us add the current user to the `dialout` group in order to run the `cu`
 without being a super-user:
-```
+```shell
 sudo adduser $USER dialout
 ```
 For the change to take effect we need to logout and login again.
@@ -72,7 +72,7 @@ There's even a default config for CHIP in `u-boot-v2023.10/configs/CHIP_defconfi
 
 Now, let's build U-Boot for CHIP:
 
-```
+```shell
 ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make CHIP_defconfig
 ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make -j$(nproc)
 ```
@@ -162,15 +162,15 @@ U-Boot release which is already great.
 At the time of writing, the latest Linux LTS kernel is 6.1.62, which we
 donwnload and extract by typing:
 
-```
+```shell
 wget -c https://cdn.kernel.org/pub/linux/kernel/v6.x/linux-6.1.62.tar.xz
 tar xf linux-6.1.62.tar.xz
 ```
 
 Let's try building with the `sunxi_defconfig` which can be found in
 `linux-6.1.62/arch/arm/configs`:
 
-```
+```shell
 cd linux-6.1.62
 ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make sunxi_defconfig
 ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make -j$(nproc) zImage
@@ -233,13 +233,13 @@ The above attempt to boot into Linux failed because we did not have a root
 filesystem (rootfs). Let's build one using Busybox!
 
 Download Busybox
-```
+```shell
 wget -c -P downlad https://busybox.net/downloads/busybox-1.36.1.tar.bz2
 tar x -C build -f download/busybox-1.36.1.tar.bz2
 ```
 
 Configure & Compile:
-```
+```shell
 cd build/busybox-1.36.1
 ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make defconfig
 sed -e 's/# CONFIG_STATIC is not set/CONFIG_STATIC=y/' -i .config
@@ -249,7 +249,7 @@ ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make CONFIG_PREFIX=./../rootfs insta
 ```
 
 Finalize initramfs:
-```
+```shell
 cat > rootfs/init << EOF
 #!/bin/sh
 mount -t proc none /proc