Subject: RE: R: [PATCH v2 4/4] dt-bindings: net: Document use of mac-address-increment

From: <[email-masked]>
Date: Sun, 20 Sep 2020 11:45:08 +0200

> On Sun, Sep 20, 2020 at 02:39:39AM +0200, [email-masked]
> wrote:
> >
> >
> > > -----Messaggio originale-----
> > > Da: Andrew Lunn <[email-masked]>
> > > Inviato: domenica 20 settembre 2020 02:31
> > > A: Ansuel Smith <[email-masked]>
> > > Cc: Miquel Raynal <[email-masked]>; Richard Weinberger
> > > <[email-masked]>; Vignesh Raghavendra <[email-masked]>; Rob
> Herring
> > > <[email-masked]>; David S. Miller <[email-masked]>; Jakub
> > > Kicinski <[email-masked]>; Heiner Kallweit <[email-masked]>;
> > > Russell King <[email-masked]>; Frank Rowand
> > > <[email-masked]>; Boris Brezillon <[email-masked]>;
> linux-
> > > [email-masked]; [email-masked]; linux-
> > > [email-masked]; [email-masked]
> > > Oggetto: 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
> >
> > Honestly the mac-address-increment-byte is added to give user some
> control
> > but I
> > don't really have a use case for it. Should I limit it to 3 or just
remove
> > the function?
> 
> If you have no use case, just remove it and document that last byte
> will be incremented. I somebody does need it, it can be added in a
> backwards compatible way.
> 
>      Andrew

I just rechecked mac-address-increment-byte and we have one device that
use it and would benefits from this.  I will change the Documentation to
min 3 and leave it.