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Message-ID: <362f1c6a8b0ec191b285ac6a604500da@walle.cc>
Date: Wed, 12 May 2021 17:27:28 +0200
From: Michael Walle <michael@...le.cc>
To: Rob Herring <robh@...nel.org>
Cc: Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
"David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Heiner Kallweit <hkallweit1@...il.com>,
Russell King <linux@...linux.org.uk>,
Frank Rowand <frowand.list@...il.com>,
Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
Ansuel Smith <ansuelsmth@...il.com>
Subject: Re: [PATCH net-next 1/3] dt-bindings: net: add
nvmem-mac-address-offset property
[adding Srinivas Kandagatla and Ansuel Smith]
Am 2021-04-16 00:27, schrieb Michael Walle:
> Am 2021-04-15 23:59, schrieb Rob Herring:
>> On Wed, Apr 14, 2021 at 05:43:49PM +0200, Andrew Lunn wrote:
>>> On Wed, Apr 14, 2021 at 05:26:55PM +0200, Michael Walle wrote:
>>> > It is already possible to read the MAC address via a NVMEM provider. But
>>> > there are boards, esp. with many ports, which only have a base MAC
>>> > address stored. Thus we need to have a way to provide an offset per
>>> > network device.
>>>
>>> We need to see what Rob thinks of this. There was recently a patchset
>>> to support swapping the byte order of the MAC address in a NVMEM. Rob
>>> said the NVMEM provider should have the property, not the MAC driver.
>>> This does seems more ethernet specific, so maybe it should be an
>>> Ethernet property?
>>
>> There was also this one[1]. I'm not totally opposed, but don't want to
>> see a never ending addition of properties to try to describe any
>> possible transformation.
>
> Agreed, that stuff like ASCII MAC address parsing should be done
> elsewhere. But IMHO adding an offset is a pretty common one (as also
> pointed out in [1]). And it also need to be a per ethernet device
> property.
I'm a bit up in the air on this, as I don't know how to proceed here.
To cite Rob from IRC:
Not really up to me. All the people that care need to come up with
something flexible enough for common/simple cases and that's not
going to get extended with every new variation. What I don't want is
a one-off that's then extended with another one-off.
I already pointed out that this property is per consumer as opposed
to something like endianess swap or parsing a given format. The latter
operates on the nvmem cell.
One random idea is to have a nvmem-cells-transformation (in the lack of
a better name) property for consumers, where you can have some kind of
simple operations like add:
nvmem-cells-transformation = <NVMEM_ADD 1>
But is that something we really want to have? I'm not sure.
btw. given that there might be other means where a base mac address can
come from in the future, it might make sense to drop the "nvmem-"
prefix and just use "mac-address-offset" (or
"base-mac-address-offset"?).
> [1]
> https://patchwork.ozlabs.org/project/devicetree-bindings/patch/20200920095724.8251-4-ansuelsmth@gmail.com/
-michael
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