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From:   <ansuelsmth@gmail.com>
To:     "'Rob Herring'" <robh+dt@kernel.org>
Cc:     "'Miquel Raynal'" <miquel.raynal@bootlin.com>,
        "'Richard Weinberger'" <richard@nod.at>,
        "'Vignesh Raghavendra'" <vigneshr@ti.com>,
        "'David S. Miller'" <davem@davemloft.net>,
        "'Jakub Kicinski'" <kuba@kernel.org>,
        "'Andrew Lunn'" <andrew@lunn.ch>,
        "'Heiner Kallweit'" <hkallweit1@gmail.com>,
        "'Russell King'" <linux@armlinux.org.uk>,
        "'Frank Rowand'" <frowand.list@gmail.com>,
        "'Boris Brezillon'" <bbrezillon@kernel.org>,
        "'MTD Maling List'" <linux-mtd@lists.infradead.org>,
        <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        "'netdev'" <netdev@vger.kernel.org>
References: <20200920095724.8251-1-ansuelsmth@gmail.com> <20200920095724.8251-4-ansuelsmth@gmail.com> <CAL_JsqKhyeh2=pJcpBKkh+s3FM__DY+VoYSYJLRUErrujTLn9A@mail.gmail.com>
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Subject: RE: [PATCH v3 3/4] of_net: add mac-address-increment support
Date:   Fri, 25 Sep 2020 20:39:30 +0200
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> -----Original Message-----
> From: Rob Herring <robh+dt@kernel.org>
> Sent: Friday, September 25, 2020 8:24 PM
> To: Ansuel Smith <ansuelsmth@gmail.com>
> Cc: Miquel Raynal <miquel.raynal@bootlin.com>; Richard Weinberger
> <richard@nod.at>; Vignesh Raghavendra <vigneshr@ti.com>; David S.
> Miller <davem@davemloft.net>; Jakub Kicinski <kuba@kernel.org>;
> Andrew Lunn <andrew@lunn.ch>; Heiner Kallweit
> <hkallweit1@gmail.com>; Russell King <linux@armlinux.org.uk>; Frank
> Rowand <frowand.list@gmail.com>; Boris Brezillon
> <bbrezillon@kernel.org>; MTD Maling List =
<linux-mtd@lists.infradead.org>;
> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; netdev
> <netdev@vger.kernel.org>
> Subject: Re: [PATCH v3 3/4] of_net: add mac-address-increment support
>=20
> On Sun, Sep 20, 2020 at 3:57 AM Ansuel Smith <ansuelsmth@gmail.com>
> wrote:
> >
> > Lots of embedded devices use the mac-address of other interface
> > extracted from nvmem cells and increments it by one or two. Add two
> > bindings to integrate this and directly use the right mac-address =
for
> > the interface. Some example are some routers that use the gmac
> > mac-address stored in the art partition and increments it by one for =
the
> > wifi. mac-address-increment-byte bindings is used to tell what byte =
of
> > the mac-address has to be increased (if not defined the last byte is
> > increased) and mac-address-increment tells how much the byte decided
> > early has to be increased.
>=20
> I'm inclined to say if there's a platform specific way to transform
> MAC addresses, then there should be platform specific code to do that
> which then stuffs the DT using standard properties. Otherwise, we have
> a never ending stream of 'generic' properties to try to handle
> different platforms' cases.
>=20
> Rob

I agree about the 'never ending stream'... But I think the increment =
feature
is not that platform specific. I will quote some number by another patch
that tried to implement the same feature in a different way, [1]

* mtd-mac-address                used 497 times in 357 device tree files
* mtd-mac-address-increment      used  74 times in  58 device tree files
* mtd-mac-address-increment-byte used   1 time  in   1 device tree file

The mtd-mac-address is what this patchset is trying to fix with the =
nvmem
support. The increment is much more than 74 times since it doesn't count
SoC that have wifi integrated (it's common practice for SoC with =
integrated
wifi to take the switch mac and use it to set the wifi mac)
Actually what is really specific is the increment-byte that can be =
dropped
if we really want to.
I still think the increment feature would be very useful to add full =
support
for mac-address extracted from nvmem cell.

[1] =
https://patchwork.ozlabs.org/project/netdev/patch/1555445100-30936-1-git-=
send-email-ynezz@true.cz/