linux-kernel - RE: [PATCH net-next 1/3] dt-bindings: net: add new properties for of_get_mac

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Message-ID: <DB8PR04MB67950A57793F62B5056DC3D3E6709@DB8PR04MB6795.eurprd04.prod.outlook.com>
Date:   Mon, 12 Apr 2021 06:38:15 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     Rob Herring <robh+dt@...nel.org>
CC:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Frank Rowand <frowand.list@...il.com>,
        netdev <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH net-next 1/3] dt-bindings: net: add new properties for
 of_get_mac_address from nvmem


Hi Rob,

> -----Original Message-----
> From: Rob Herring <robh+dt@...nel.org>
> Sent: 2021年4月9日 21:50
> To: Joakim Zhang <qiangqing.zhang@....com>
> Cc: David Miller <davem@...emloft.net>; Jakub Kicinski <kuba@...nel.org>;
> Andrew Lunn <andrew@...n.ch>; Heiner Kallweit <hkallweit1@...il.com>;
> Russell King <linux@...linux.org.uk>; Frank Rowand
> <frowand.list@...il.com>; netdev <netdev@...r.kernel.org>;
> devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; dl-linux-imx
> <linux-imx@....com>
> Subject: Re: [PATCH net-next 1/3] dt-bindings: net: add new properties for
> of_get_mac_address from nvmem
> 
> On Fri, Apr 9, 2021 at 4:07 AM Joakim Zhang <qiangqing.zhang@....com>
> wrote:
> >
> > From: Fugang Duan <fugang.duan@....com>
> >
> > Currently, of_get_mac_address supports NVMEM, some platforms
> 
> What's of_get_mac_address? This is a binding patch. Don't mix Linux things in
> it.

Ok, will improve it.

> > MAC address that read from NVMEM efuse requires to swap bytes order,
> > so add new property "nvmem_macaddr_swap" to specify the behavior. If
> > the MAC address is valid from NVMEM, add new property
> > "nvmem-mac-address" in ethernet node.
> >
> > Update these two properties in the binding documentation.
> >
> > Signed-off-by: Fugang Duan <fugang.duan@....com>
> > Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> > ---
> >  .../bindings/net/ethernet-controller.yaml          | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> >
> > diff --git
> > a/Documentation/devicetree/bindings/net/ethernet-controller.yaml
> > b/Documentation/devicetree/bindings/net/ethernet-controller.yaml
> > index e8f04687a3e0..c868c295aabf 100644
> > --- a/Documentation/devicetree/bindings/net/ethernet-controller.yaml
> > +++ b/Documentation/devicetree/bindings/net/ethernet-controller.yaml
> > @@ -32,6 +32,15 @@ properties:
> >        - minItems: 6
> >          maxItems: 6
> >
> > +  nvmem-mac-address:
> > +    allOf:
> > +      - $ref: /schemas/types.yaml#definitions/uint8-array
> > +      - minItems: 6
> > +        maxItems: 6
> > +    description:
> > +      Specifies the MAC address that was read from nvmem-cells and
> dynamically
> > +      add the property in device node;
> 
> Why can't you use local-mac-address or mac-address? Those too can come
> from some other source.

I also don't understand what Andy's do for this, per his commit message "If the MAC address is valid from NVMEM, add new property "nvmem-mac-address" in ethernet node.".
He said this done _DYNAMICALLY_, but I have not found where ""nvmem-mac-address" property been added, and can't find it from ethernet node. So I send out patch first to see if reviewers
can give a hint, or point out this is actually incorrect.
  
> > +
> >    max-frame-size:
> >      $ref: /schemas/types.yaml#/definitions/uint32
> >      description:
> > @@ -52,6 +61,11 @@ properties:
> >    nvmem-cell-names:
> >      const: mac-address
> >
> > +  nvmem_macaddr_swap:
> > +    $ref: /schemas/types.yaml#/definitions/flag
> > +    description:
> > +      swap bytes order for the 6 bytes of MAC address
> 
> So 'nvmem-mac-address' needs to be swapped or it's swapped before writing?
> In any case, this belongs in the nvmem provider.

MAC address read from NVMEM cell needs to be swapped. The order of bytes that NVMEM provider provided is fixed, so I think we should swap at the NVMEM consumer side.
It is more reasonable and common add a property in Documentation/devicetree/bindings/nvmem/nvmem-consumer.yaml, and swap the data in nvmem_cell_read() function.

Best Regards,
Joakim Zhang
> Rob