build a new kernel for ARM7 CHIP

build_arm7_kernel.sh

#!/bin/bash
# The first argument should be the path to the existing
# kernel .config file you'd like to use as a baseline.
# Inspired by http://www.raspibo.org/wiki/index.php/Compile_the_Linux_kernel_for_Chip:_my_personal_HOWTO

# practice safe bash
set -e
set -u
set -o pipefail

# show bash debug output
set -x

kernelver="4.4.13"
configpath="$1"

if [ -z "${configpath}" ]; then
    echo "Specify the path to .config"
    exit 1
fi

workdir="/tmp/buildchip"
mkdir -p "${workdir}"
libdir=$(mktemp -d)
assemblydir=$(mktemp -d)
kerneldir="${workdir}/CHIP-linux"
wifidir="${workdir}/RTL8723BS"

function cleanup {
    # remove temporarily directories
    rm -r "${libdir}" "${assemblydir}"
}
trap cleanup EXIT

# retrieve the desired branch of CHIP kernel source
if [ ! -d "${kerneldir}" ]; then
    git clone https://github.com/NextThingCo/CHIP-linux.git -b debian/4.4.13-ntc-mlc --single-branch $kerneldir
fi

# move .config into kernel path
cp "${configpath}" "${kerneldir}/.config"

# start interactive configuration
(cd "${kerneldir}" && make ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabihf- menuconfig)

# retrieve the kernel build suffix from config line similar to
# CONFIG_LOCALVERSION="bunn001"
suffix=$(grep -Po "(?<=CONFIG_LOCALVERSION=\")(\w+)" "${kerneldir}/.config")

# cross-compile kernel and modules
(cd "${kerneldir}" && make ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabihf- -j 9)

# install kernel modules to $libdir
(cd $kerneldir && make ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabihf- INSTALL_MOD_PATH=$libdir modules_install)

# retrieve RTL8723BS kernel source, debian branch
if [ ! -d "${wifidir}" ]; then
    git clone https://github.com/NextThingCo/RTL8723BS.git -b debian --single-branch $wifidir
    # apply debian patches to RTL8723BS source
    (cd "${wifidir}" && for i in debian/patches/0*; do  echo $i; patch -p 1 <$i ; done)
fi

# cross-compile module
(cd "${wifidir}" && make -j 9 CONFIG_PLATFORM_ARM_SUNxI=y ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabihf- -C "${kerneldir}" M="${PWD}" CONFIG_RTL8723BS=m  INSTALL_MOD_PATH="${libdir}")

# install module to $libdir
(cd "${wifidir}" && make -j 9 CONFIG_PLATFORM_ARM_SUNxI=y ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabihf- -C "${kerneldir}" M="${PWD}" CONFIG_RTL8723BS=m  INSTALL_MOD_PATH=$libdir modules_install)

# set up package for transport
(cd "${assemblydir}" && mkdir -p boot lib/modules lib/firmware)
cp "${kerneldir}/arch/arm/boot/zImage" "${assemblydir}/boot/vmlinuz-${kernelver}${suffix}+"
cp "${kerneldir}/.config" "${assemblydir}/boot/config-${kernelver}${suffix}+"
cp "${kerneldir}/System.map" "${assemblydir}/boot/System.map-${kernelver}${suffix}+"
cp -r "${libdir}/lib/modules" "${assemblydir}/lib/"

if [ -d "${libdir}/firmware" ]; then
    cp -r "${libdir}/firmware" "${assemblydir}/lib/"
fi

# create a tar that can be untarred on the CHIP with
# sudo tar -C / -xzvf "4.4.13${suffix}.tar.gz"
tar -C "${assemblydir}" -cvzf "${kernelver}${suffix}.tar.gz" boot lib