Best path to a custom kernel on arm?

General Discussion
8

this is the boot.cmd:

# DO NOT EDIT THIS FILE
#
# Please edit /boot/armbianEnv.txt to set supported parameters
#

setenv load_addr "0x9000000"
setenv overlay_error "false"
# default values
setenv rootdev "/dev/mmcblk0p1"
setenv verbosity "1"
setenv console "both"
setenv bootlogo "false"
setenv rootfstype "ext4"
setenv docker_optimizations "on"
setenv earlycon "off"

echo "Boot script loaded from ${devtype} ${devnum}"

if test -e ${devtype} ${devnum} ${prefix}armbianEnv.txt; then
        load ${devtype} ${devnum} ${load_addr} ${prefix}armbianEnv.txt
        env import -t ${load_addr} ${filesize}
fi

if test "${logo}" = "disabled"; then setenv logo "logo.nologo"; fi

if test "${console}" = "display" || test "${console}" = "both"; then setenv consoleargs "console=tty1"; fi
if test "${console}" = "serial" || test "${console}" = "both"; then setenv consoleargs "console=ttyS2,1500000 ${consoleargs}"; fi
if test "${earlycon}" = "on"; then setenv consoleargs "earlycon ${consoleargs}"; fi
if test "${bootlogo}" = "true"; then setenv consoleargs "bootsplash.bootfile=bootsplash.armbian ${consoleargs}"; fi

# get PARTUUID of first partition on SD/eMMC the boot script was loaded from
if test "${devtype}" = "mmc"; then part uuid mmc ${devnum}:1 partuuid; fi

setenv bootargs "root=${rootdev} rootwait rootfstype=${rootfstype} ${consoleargs} consoleblank=0 loglevel=${verbosity} ubootpart=${partuuid} usb-storage.quirks=${usbstoragequirks} ${extraargs} ${extraboardargs}"

if test "${docker_optimizations}" = "on"; then setenv bootargs "${bootargs} cgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory swapaccount=1"; fi

load ${devtype} ${devnum} ${ramdisk_addr_r} ${prefix}uInitrd
load ${devtype} ${devnum} ${kernel_addr_r} ${prefix}Image

load ${devtype} ${devnum} ${fdt_addr_r} ${prefix}dtb/${fdtfile}
fdt addr ${fdt_addr_r}
fdt resize 65536
for overlay_file in ${overlays}; do
        if load ${devtype} ${devnum} ${load_addr} ${prefix}dtb/rockchip/overlay/${overlay_prefix}-${overlay_file}.dtbo; then
                echo "Applying kernel provided DT overlay ${overlay_prefix}-${overlay_file}.dtbo"
                fdt apply ${load_addr} || setenv overlay_error "true"
        fi
done
for overlay_file in ${user_overlays}; do
        if load ${devtype} ${devnum} ${load_addr} ${prefix}overlay-user/${overlay_file}.dtbo; then
                echo "Applying user provided DT overlay ${overlay_file}.dtbo"
                fdt apply ${load_addr} || setenv overlay_error "true"
        fi
done
if test "${overlay_error}" = "true"; then
        echo "Error applying DT overlays, restoring original DT"
        load ${devtype} ${devnum} ${fdt_addr_r} ${prefix}dtb/${fdtfile}
else
        if load ${devtype} ${devnum} ${load_addr} ${prefix}dtb/rockchip/overlay/${overlay_prefix}-fixup.scr; then
                echo "Applying kernel provided DT fixup script (${overlay_prefix}-fixup.scr)"
                source ${load_addr}
        fi
        if test -e ${devtype} ${devnum} ${prefix}fixup.scr; then
                load ${devtype} ${devnum} ${load_addr} ${prefix}fixup.scr
                echo "Applying user provided fixup script (fixup.scr)"
                source ${load_addr}
        fi
fi
booti ${kernel_addr_r} ${ramdisk_addr_r} ${fdt_addr_r}

# Recompile with:
# mkimage -C none -A arm -T script -d /boot/boot.cmd /boot/boot.scr