linux-kernel - Re: [PATCH v2 4/4] dt-bindings: net: Document use of mac-address-increment

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Message-ID: <20200920003128.GC3673389@lunn.ch>
Date:   Sun, 20 Sep 2020 02:31:28 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Ansuel Smith <ansuelsmth@...il.com>
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.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>,
        Boris Brezillon <bbrezillon@...nel.org>,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2 4/4] dt-bindings: net: Document use of
 mac-address-increment

> +  mac-address-increment:
> +    description:
> +      The MAC address can optionally be increased (or decreased using
> +      negative values) from the original value readed (from a nvmem cell

Read is irregular, there is no readed, just read.

> +      for example). This can be used if the mac is readed from a dedicated
> +      partition and must be increased based on the number of device
> +      present in the system.

You should probably add there is no underflow/overflow to other bytes
of the MAC address. 00:01:02:03:04:ff + 1 == 00:01:02:03:04:00.

> +    minimum: -255
> +    maximum: 255
> +
> +  mac-address-increment-byte:
> +    description:
> +      If 'mac-address-increment' is defined, this will tell what byte of
> +      the mac-address will be increased. If 'mac-address-increment' is
> +      not defined, this option will do nothing.
> +    default: 5
> +    minimum: 0
> +    maximum: 5

Is there a real need for this? A value of 0 seems like a bad idea,
since a unicast address could easily become a multicast address, which
is not valid for an interface address. It also does not seem like a
good idea to allow the OUI to be changed. So i think only bytes 3-5
should be allowed, but even then, i don't think this is needed, unless
you do have a clear use case.

    Andrew