linux-kernel - [PATCH V3 1/6] dt-bindings: nvmem: layouts: add U-Boot environment variables layout

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Message-Id: <20231221173421.13737-1-zajec5@gmail.com>
Date: Thu, 21 Dec 2023 18:34:16 +0100
From: Rafał Miłecki <zajec5@...il.com>
To: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Michael Walle <michael@...le.cc>,
	Miquel Raynal <miquel.raynal@...tlin.com>,
	linux-mtd@...ts.infradead.org,
	devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	u-boot@...ts.denx.de,
	Rafał Miłecki <rafal@...ecki.pl>
Subject: [PATCH V3 1/6] dt-bindings: nvmem: layouts: add U-Boot environment variables layout

From: Rafał Miłecki <rafal@...ecki.pl>

U-Boot env data is a way of storing firmware variables. It's a format
that can be used of top of various storage devices. Its binding should
be an NVMEM layout instead of a standalone device.

This patch adds layout binding which allows using it on top of MTD NVMEM
device as well as any other. At the same time it deprecates the old
combined binding.

Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
---
V2: Add "-layout" suffix to compatibles to avoid conflict

 .../nvmem/layouts/u-boot,env-layout.yaml      | 55 +++++++++++++++++++
 .../devicetree/bindings/nvmem/u-boot,env.yaml |  6 ++
 2 files changed, 61 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/nvmem/layouts/u-boot,env-layout.yaml

diff --git a/Documentation/devicetree/bindings/nvmem/layouts/u-boot,env-layout.yaml b/Documentation/devicetree/bindings/nvmem/layouts/u-boot,env-layout.yaml
new file mode 100644
index 000000000000..3b4d8f2a44e1
--- /dev/null
+++ b/Documentation/devicetree/bindings/nvmem/layouts/u-boot,env-layout.yaml
@@ -0,0 +1,55 @@
+# SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/nvmem/layouts/u-boot,env-layout.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: NVMEM layout of U-Boot environment variables
+
+maintainers:
+  - Rafał Miłecki <rafal@...ecki.pl>
+
+description:
+  U-Boot uses environment variables to store device parameters and
+  configuration. They may be used for booting process, setup or keeping end user
+  info.
+
+  Data is stored using U-Boot specific formats (variant specific header and NUL
+  separated key-value pairs).
+
+properties:
+  compatible:
+    oneOf:
+      - description: A standalone env data block
+        const: u-boot,env-layout
+      - description: Two redundant blocks with active one flagged
+        const: u-boot,env-redundant-bool-layout
+      - description: Two redundant blocks with active having higher counter
+        const: u-boot,env-redundant-count-layout
+      - description: Broadcom's variant with custom header
+        const: brcm,env-layout
+
+additionalProperties: false
+
+examples:
+  - |
+    partitions {
+        compatible = "fixed-partitions";
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        partition@0 {
+            reg = <0x0 0x40000>;
+            label = "u-boot";
+            read-only;
+        };
+
+        partition@...00 {
+            reg = <0x40000 0x10000>;
+            label = "u-boot-env";
+
+            nvmem-layout {
+                compatible = "u-boot,env-layout";
+            };
+        };
+    };
diff --git a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
index 9c36afc7084b..6c2a3ca5f051 100644
--- a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
+++ b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
@@ -26,9 +26,15 @@ description: |
 
   Variables can be defined as NVMEM device subnodes.
 
+  Introduction of NVMEM layouts exposed a limitation of this binding design.
+  Description of NVMEM data content should be separated from NVMEM devices.
+  Since the introduction of U-Boot env data layout this binding is deprecated.
+
 maintainers:
   - Rafał Miłecki <rafal@...ecki.pl>
 
+deprecated: true
+
 properties:
   compatible:
     oneOf:
-- 
2.35.3