Quick 'n dirty DT integration for Debian

11_devicetree

#!/bin/sh

#
# /etc/grub.d/11_devicetree
#
# Scan the devicetree file available in /boot and construct menu entries
# for them.
#
# This script has a fewer smart features compared to normal grub scripts.
# In particular it must be configured differently for boot-in-root and
# separate boot (a.k.a.  encrypted rootfs) scenarios.
#
# We are relying on the Debian theme code to look up the /boot partition so
# that we can load a devicetree from them. We could do something like the
# following but I'm too busy right now to lookup how Debian's grub scripts
# find that UUID!
#
#     insmod part_gpt
#     insmod ext2
#     search --no-floppy --fs-uuid --set=root c741fdf7-37fa-4269-a1bc-246ef13d8871
#

# This configuration is correct for encrypted rootfs (and Thinkpad X13s)
grub_boot=/
linux_boot=/boot/
dtb=sc8280xp-lenovo-thinkpad-x13s.dtb

# Select a default dtb. This file is strictly manually managed and, if absent,
# then we'll simply assume DtbLoader is still doing it's (pointless) thing!
if [ -e "${linux_boot}${dtb}" ]
then
	echo devicetree ${grub_boot}${dtb}
fi

# Update the set of DTs in /boot
for d in /usr/lib/linux-image-*/qcom/${dtb}
do
	tag=$(echo ${d} | cut -d/ -f4 | cut -c12-)
	if [ ! -e ${linux_boot}${dtb}${tag} ]
	then
		cp ${d} ${linux_boot}${dtb}${tag}
	fi
done

# Generate menu items to allow replacing the DTB with specific versions
if [ ! -z $(ls ${linux_boot}${dtb}-* | wc -l) ]
then
	echo "submenu 'Devicetree recovery options for Debian/GNU/Linux' {"
	for d in $(ls -r ${linux_boot}${dtb}-*)
	do
		d="$(basename ${d})"
		echo "	menuentry 'Replace DT with $d' {"
		echo "		devicetree ${grub_boot}${d}"
		echo "	}"
	done
	echo "}"
fi