linux-kernel - [PATCH] docs: devicetree: overlay-notes: recommend top-level compatible in DTSO

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <20250624181320.2810521-1-raymond.mao@linaro.org>
Date: Tue, 24 Jun 2025 11:13:20 -0700
From: Raymond Mao <raymond.mao@...aro.org>
To: linux-doc@...r.kernel.org
Cc: Raymond Mao <raymond.mao@...aro.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] docs: devicetree: overlay-notes: recommend top-level compatible in DTSO

When managing multiple base device trees and overlays in a structured
way (e.g. bundled in firmware or tools), it is helpful to identify the
intended target base DT for each overlay, which can be done via a
top-level compatible string in the overlay.

This patch updates the document with a note and example for this
practice.

Signed-off-by: Raymond Mao <raymond.mao@...aro.org>
---
 Documentation/devicetree/overlay-notes.rst | 28 ++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/Documentation/devicetree/overlay-notes.rst b/Documentation/devicetree/overlay-notes.rst
index 35e79242af9a..30b142d1b2ee 100644
--- a/Documentation/devicetree/overlay-notes.rst
+++ b/Documentation/devicetree/overlay-notes.rst
@@ -103,6 +103,34 @@ The above bar.dtso example modified to use target path syntax is::
     ---- bar.dtso --------------------------------------------------------------
 
 
+Overlay identification
+----------------------
+
+When managing overlays dynamically or bundling multiple base device trees
+and overlays in a single system (e.g., in firmware, initramfs, or user-space
+tools), it becomes important to associate each overlay with its intended
+target base DT.
+
+To support this, overlays should include the top-level compatible string
+from its base DT.
+This enables higher-level software or firmware to identify which base DT
+an overlay is compatible with and apply it accordingly.
+
+Example usage::
+
+    ---- bar.dtso - overlay with top-level compatible string -------------------
+	/dts-v1/;
+	/plugin/;
+	compatible = "corp,foo";
+
+	...
+    ---- bar.dtso --------------------------------------------------------------
+
+This top-level compatible string is not required by the kernel overlay
+mechanism itself, but it is strongly recommended for managing overlays in
+scalable systems.
+
+
 Overlay in-kernel API
 --------------------------------
 
-- 
2.25.1