linux-kernel - [PATCH] dt-bindings: nvmem: add U-Boot environment variables binding

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Message-Id: <20220215134925.32691-1-zajec5@gmail.com>
Date:   Tue, 15 Feb 2022 14:49:25 +0100
From:   Rafał Miłecki <zajec5@...il.com>
To:     Rob Herring <robh+dt@...nel.org>, Tom Rini <trini@...sulko.com>
Cc:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Ricardo Salveti <ricardo@...ndries.io>,
        Michal Simek <michal.simek@...inx.com>,
        Jorge Ramirez-Ortiz <jorge@...ndries.io>,
        devicetree@...r.kernel.org, u-boot@...ts.denx.de,
        linux-kernel@...r.kernel.org,
        Rafał Miłecki <rafal@...ecki.pl>
Subject: [PATCH] dt-bindings: nvmem: add U-Boot environment variables binding

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

U-Boot uses environment variables for storing device setup data on
flash. That data usually needs to be accessed by a bootloader, kernel
and often user-space.

This binding allows describing environment data location and its format
clearly. In some/many cases it should be cleaner than hardcoding &
duplicating that info in multiple places. Bootloader & kernel can share
DTS and user-space can try reading it too or just have correct data
exposed by a kernel.

Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
---
 .../devicetree/bindings/nvmem/u-boot,env.yaml | 58 +++++++++++++++++++
 MAINTAINERS                                   |  5 ++
 2 files changed, 63 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/nvmem/u-boot,env.yaml

diff --git a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
new file mode 100644
index 000000000000..a2b3a9b88eb8
--- /dev/null
+++ b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
@@ -0,0 +1,58 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/nvmem/u-boot,env.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: U-Boot environment variables
+
+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 on flash in a U-Boot specific format (header and NUL separated
+  key-value pairs).
+
+  This binding allows specifying data location and used format.
+
+maintainers:
+  - Rafał Miłecki <rafal@...ecki.pl>
+
+allOf:
+  - $ref: nvmem.yaml#
+
+properties:
+  compatible:
+    oneOf:
+      - description: A standalone env data block
+        const: u-boot,env
+      - description: Two redundant blocks with active one flagged
+        const: u-boot,env-redundant-bool
+      - description: Two redundant blocks with active having higher counter
+        const: u-boot,env-redundant-count
+
+  reg:
+    maxItems: 1
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    partitions {
+        compatible = "fixed-partitions";
+        #address-cells = <1>;
+        #size-cells = <1>;
+
+        partition@0 {
+            label = "u-boot";
+            reg = <0x0 0x40000>;
+            read-only;
+        };
+
+        partition@...00 {
+            compatible = "u-boot,env";
+            label = "u-boot-env";
+            reg = <0x40000 0x10000>;
+        };
+    };
diff --git a/MAINTAINERS b/MAINTAINERS
index d20344ab7900..2f07f1d2290a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -19905,6 +19905,11 @@ W:	http://linuxtv.org
 T:	git git://linuxtv.org/media_tree.git
 F:	drivers/media/pci/tw686x/
 
+U-BOOT ENVIRONMENT VARIABLES
+M:	Rafał Miłecki <rafal@...ecki.pl>
+S:	Maintained
+F:	Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
+
 UACCE ACCELERATOR FRAMEWORK
 M:	Zhangfei Gao <zhangfei.gao@...aro.org>
 M:	Zhou Wang <wangzhou1@...ilicon.com>
-- 
2.34.1