linux-kernel - [PATCH 1/2] dt-bindings: net: ethernet-controller: Add mac offset option

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Message-Id: <20241220-net-mac-nvmem-offset-v1-1-e9d1da2c1681@linaro.org>
Date: Fri, 20 Dec 2024 20:17:06 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Andrew Lunn <andrew@...n.ch>, 
 Heiner Kallweit <hkallweit1@...il.com>, 
 Russell King <linux@...linux.org.uk>, Simon Horman <horms@...nel.org>
Cc: netdev@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH 1/2] dt-bindings: net: ethernet-controller: Add mac offset
 option

In practice (as found in the OpenWrt project) many devices
with multiple ethernet interfaces just store a base MAC
address in NVMEM and increase the lowermost byte with one for
each interface, so as to occupy less NVMEM.

Support this with a per-interface offset so we can encode
this in a predictable way for each interface sharing the
same NVMEM cell.

Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
---
 .../devicetree/bindings/net/ethernet-controller.yaml         | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Documentation/devicetree/bindings/net/ethernet-controller.yaml b/Documentation/devicetree/bindings/net/ethernet-controller.yaml
index 45819b2358002bc75e876eddb4b2ca18017c04bd..608f89359ca844e5325e3cc81bd2677b0eccb08a 100644
--- a/Documentation/devicetree/bindings/net/ethernet-controller.yaml
+++ b/Documentation/devicetree/bindings/net/ethernet-controller.yaml
@@ -53,6 +53,18 @@ properties:
   nvmem-cell-names:
     const: mac-address

+  nvmem-mac-minor-offset:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 1
+    maximum: 255
+    description:
+      When a MAC address for a device with multiple ethernet interface
+      is stored in non-volatile memory, the address is often offsetted
+      for different interfaces by increasing the lowermost byte for each
+      interface subsequent to the first in order to save space in NVMEM.
+      This property can be used to add that offset when several
+      interfaces refer to the same NVMEM cell.
+
   phy-connection-type:
     description:
       Specifies interface type between the Ethernet device and a physical

-- 
2.47.1