Speaker
Description
Device Tree has been extremely successful at describing non-discoverable hardware in Linux and other embedded systems. However, it remains fundamentally monolithic: each Device Tree describes a complete system, and reuse across independently developed hardware components is limited.
This becomes problematic for modular platforms where expansion boards, mezzanines, daughter cards, or hot-pluggable hardware are expected to work across multiple base boards. While Device Tree Overlays provide a mechanism to modify an existing hardware description, they require detailed knowledge of the target system. They do not offer a robust way to describe addon boards independently of the base platform nor a way to use the same addon board description to describe the same board connected on multiple connectors available on a single base board.
The recently proposed Device Tree Addon format [1] aims to address those limitations. It allows a single addon DTB to describe an extension board that can be used on different connectors of a given base board, or on different base boards, without requiring board-specific customization.
The design goal of Device Tree Addon is illustrated in slides used for a talk given at ELCE 2025 [2]. The relevant slides sections are the following:
- Use case and goals
- The connector abstraction.
The "Connector: current status" section available in [2] is now obsolete. The Device Tree Addon concept emerged from discussions [3] that followed the ELCE 2025 conference.
This session will briefly present Device Tree Addon concepts recently
introduced and available in the RFC implementation [1]. Beyond introducing the format, the focus will be on the remaining challenges that must be addressed before broader adoption.
Topics for discussion include remaining design questions, integration with
Device Tree bindings and validation rules, standardization efforts in Devicetree Specification (DTSpec). We will also examine the work still required in dtc, libfdt, bootloaders, and the Linux kernel.
The goal of the session is to gather feedback from Device Tree maintainers,
kernel developers, bootloader developers, and users of modular hardware platforms to help shape the future direction of Device Tree Addons.
[1] https://lore.kernel.org/all/20260112142009.1006236-1-herve.codina@bootlin.com/
[2] https://bootlin.com/pub/conferences/2025/elce/ceresoli-hotplug-status.pdf
[3] https://lore.kernel.org/all/20250902105710.00512c6d@booty/