[PATCH V4] dt-bindings: nvmem: fixed-cell: add compatible for MAC cells

[Rob Herring]

On Tue, 27 Jun 2023 22:46:30 +0200, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal at milecki.pl>
> 
> A lot of home routers have NVMEM fixed cells containing MAC address that
> need some further processing. In ~99% cases MAC needs to be:
> 1. Optionally parsed from ASCII format
> 2. Increased by a vendor-picked value
> 
> There was already an attempt to design a binding for that at NVMEM
> device level in the past. It wasn't accepted though as it didn't really
> fit NVMEM device layer.
> 
> The introduction of NVMEM fixed-cells layout seems to be an opportunity
> to provide a relevant binding in a clean way.
> 
> This commit adds a *generic* compatible string: "mac-base". As always it
> needs to be carefully reviewed.
> 
> OpenWrt project currently supports ~300 home routers that have NVMEM
> cell with binary-stored base MAC.T hose devices are manufactured by
> multiple vendors. There are TP-Link devices (76 of them), Netgear (19),
> D-Link (11), OpenMesh (9), EnGenius (8), GL.iNet (8), ZTE (7),
> Xiaomi (5), Ubiquiti (6) and more. Those devices don't share an
> architecture or SoC.
> 
> Another 200 devices have base MAC stored in an ASCII format (not all
> those devices have been converted to DT though).
> 
> It would be impractical to provide unique "compatible" strings for NVMEM
> layouts of all those devices. It seems like a valid case for allowing a
> generic binding instead. Even if this binding will not be sufficient for
> some further devices it seems to be useful enough as it is.
> 
> Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
> ---
> V2: Drop "mac-ascii" as length can be checked instead
>     Fix "allOf" by adding required: [ compatible ]
> V3: Fix cell length in "description" (thank you Rob!)
> V4: Fix cell length (12 → 6) in fixed-layout.yaml example as well
> ---
>  .../bindings/nvmem/layouts/fixed-cell.yaml    | 26 +++++++++++++++++++
>  .../bindings/nvmem/layouts/fixed-layout.yaml  | 12 +++++++++
>  .../devicetree/bindings/nvmem/nvmem.yaml      |  5 +++-
>  3 files changed, 42 insertions(+), 1 deletion(-)
> 

Reviewed-by: Rob Herring <robh at kernel.org>