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dtbloader

dtbloader is an EFI driver that finds and installs DeviceTree into the UEFI configuration table.

Since most existing Windows-on-Arm devices focus on Windows, they use ACPI to boot. In many cases though this ACPI is hard or impossible to use with Linux so instead DT should be used. dtbloader attemtps to simplify running Linux-based or other OS that use DT by providing:

  • Device detection that uses DMI to pick which DTB should be used.
  • Device-specific DT fixups to allow tailoring generic dtb to a given device (i.e. set hw variants, MAC...)
  • DT Fixup protocol to allow bootloaders like sd-boot to load their own dtb while still applying the fixups.

Supported devices

  • Acer Aspire 1
  • ASUS Vivobook S 15
  • Dell XPS 13 9345
  • HP Omnibook X 14
  • Lenovo Flex 5G
  • Lenovo Miix 630
  • Lenovo ThinkPad T14s Gen 6
  • Lenovo ThinkPad X13s Gen 1
  • Lenovo Yoga 5G
  • Lenovo Yoga C630
  • Lenovo Yoga Slim 7x
  • Microsoft Surface Pro 9 5G
  • Microsoft Windows Dev Kit 2023
  • QTI Snapdragon Devkit for Windows (x1e)

(Note: Devices marked with italic may not be available in upstream Linux or linux-next yet.)

Adding new devices

To add a new device, run scripts/describe_hw.sh on the target device and place the output into a new file in src/devices. The script will automatically generate a template device description for you. To specify which dtb should be used, run it like this:

$ sudo scripts/describe_hw.sh -d "qcom/sc8280xp-lenovo-thinkpad-x13s.dtb"

Building

Make sure you have submodules:

git submodule update --init --recursive

Then build the project:

make -j$(nproc)

Use make DEBUG=1 to enable additional log messages.

Note that dtbloader uses clang and lld to be built. You may also need additional tools from llvm package.

Usage

To manually install dtbloader, copy the file to ESP, boot into efi shell, then:

# Switch to the ESP partition (replace fs0 with yours)
Shell:\> fs0:
# Install the driver into the boot order
fs0:\> bcfg driver add 1 dtbloader.efi "dtbloader"
# On some devices you may need to add optional data
# to the driver entry for firmware to load it.
fs0:\> echo none > tmp.txt
fs0:\> bcfg driver -opt 1 tmp.txt
fs0:\> rm tmp.txt

Alternatively, some bootloaders such as systemd-boot provide driver boot directory. If you use sd-boot, you may place dtbloader.efi to ESP as /EFI/systemd/drivers/dtbloaderaa64.efi (where aa64 is the arch suffix).

dtbloader will look for the dtb files in the partition it was installed on. It will look into: /dtbloader/dtbs/; dtbs/; / in order of priority.

Warning

Some WoA devices keep full bootloader chain on the same eMMC/UFS as the OS. Make sure to never tamper with bootloader related partitions.

Tip

If SecureBoot is enabled, dtbloader will save the DTB hash into an uefi varialbe and show a warning in case the hash changes. Hash will be updated automatically after.

Acknowledgements

This project is a reimplementation of the original DtbLoader.efi from the aarch64-laptops project. However while the original implementation used specially-named dtb files to discover the compatible dtb, this one keeps a database of compatible devices to match to the conventional dtb name.