linux-kernel - [PATCH] dt-bindings: nvmem: convert U-Boot env to a layout

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Message-Id: <20240705225821.13196-1-zajec5@gmail.com>
Date: Sat,  6 Jul 2024 00:58:21 +0200
From: Rafał Miłecki <zajec5@...il.com>
To: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.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>,
	devicetree@...r.kernel.org,
	linux-mtd@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org,
	u-boot@...ts.denx.de,
	linux-kernel@...r.kernel.org,
	Rafał Miłecki <rafal@...ecki.pl>
Subject: [PATCH] dt-bindings: nvmem: convert U-Boot env to a layout

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

U-Boot environment variables can be stored in various data sources. MTD
is just one of available options. Refactor DT binding into a layout so
it can be used with UBI volumes and other NVMEM devices.

Link: https://lore.kernel.org/all/20231221173421.13737-1-zajec5@gmail.com/
Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
---
I'm sending this PATCH without Linux changes to see if this is the
right approach - for developers and (DT) maintainers to review it first.

My previous attempt (see above Link) turned out in refusal so I'm just
trying to save some time in case this one goes wrong as well.

Hopefully the included example (which I really think we should add)
explains well how I think this binding should be used with layouts.

If I get some positive feedback I'll work on V2 with actual Linux
changes.

 .../bindings/nvmem/layouts/nvmem-layout.yaml  |  1 +
 .../nvmem/{ => layouts}/u-boot,env.yaml       | 39 ++++++++++++++++---
 2 files changed, 35 insertions(+), 5 deletions(-)
 rename Documentation/devicetree/bindings/nvmem/{ => layouts}/u-boot,env.yaml (75%)

diff --git a/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml b/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml
index 3b40f7880774..382507060651 100644
--- a/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml
+++ b/Documentation/devicetree/bindings/nvmem/layouts/nvmem-layout.yaml
@@ -21,6 +21,7 @@ oneOf:
   - $ref: fixed-layout.yaml
   - $ref: kontron,sl28-vpd.yaml
   - $ref: onie,tlv-layout.yaml
+  - $ref: u-boot,env.yaml
 
 properties:
   compatible: true
diff --git a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml b/Documentation/devicetree/bindings/nvmem/layouts/u-boot,env.yaml
similarity index 75%
rename from Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
rename to Documentation/devicetree/bindings/nvmem/layouts/u-boot,env.yaml
index 9c36afc7084b..56a8f55d4a09 100644
--- a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
+++ b/Documentation/devicetree/bindings/nvmem/layouts/u-boot,env.yaml
@@ -1,10 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
 %YAML 1.2
 ---
-$id: http://devicetree.org/schemas/nvmem/u-boot,env.yaml#
+$id: http://devicetree.org/schemas/nvmem/layouts/u-boot,env.yaml#
 $schema: http://devicetree.org/meta-schemas/core.yaml#
 
-title: U-Boot environment variables
+title: U-Boot environment variables layout
 
 description: |
   U-Boot uses environment variables to store device parameters and
@@ -21,9 +21,6 @@ description: |
   This binding allows marking storage device (as containing env data) and
   specifying used format.
 
-  Right now only flash partition case is covered but it may be extended to e.g.
-  UBI volumes in the future.
-
   Variables can be defined as NVMEM device subnodes.
 
 maintainers:
@@ -42,6 +39,7 @@ properties:
         const: brcm,env
 
   reg:
+    description: Partition offset and size for env on top of MTD
     maxItems: 1
 
   bootcmd:
@@ -58,6 +56,17 @@ properties:
         description: The first argument is a MAC address offset.
         const: 1
 
+allOf:
+  - if:
+      properties:
+        $nodename:
+          not:
+            contains:
+              pattern: "^partition@[0-9a-f]+$"
+    then:
+      properties:
+        reg: false
+
 additionalProperties: false
 
 examples:
@@ -101,3 +110,23 @@ examples:
             };
         };
     };
+  - |
+    partition@0 {
+        reg = <0x0 0x100000>;
+        label = "ubi";
+        compatible = "linux,ubi";
+
+        volumes {
+            ubi-volume-u-boot-env {
+                volname = "env";
+
+                nvmem-layout {
+                    compatible = "u-boot,env";
+
+                    ethaddr {
+                        #nvmem-cell-cells = <1>;
+                    };
+                };
+            };
+        };
+    };
-- 
2.35.3