[U-Boot-Users] MAC address question...

Wolfgang Denk wd at denx.de
Thu Aug 26 23:58:51 CEST 2004

Dear Ladislav,

in message <20040826205439.GA2670 at umax645sx> you wrote:
> I'm getting clueless now. You don't like new command approach and you
> also don't like setenv ethaddr approach. I think there are people, who
> are solving similar problem. If there is no way to add this feature
> into official U-Boot, just say it directly and I'm fine with keeping
> patches localy.

I'm not against this feature, I just see no sense  in  adding  a  new
command.  Either you can script this using existing "i2c" or "eeprom"
or "mm" commands, or you can use a separate standalone application as
done for the 82559 and eepro100 cards.

> 1) MAC adress lives in EEPROM connected to SMC ethernet chip. This
>    address comes from purchased range.

OK, then there is no need to change it, right?

> 2) User is able to change it in enviroment, but is unable to save it
>    together with other enviroment variables and he is also unable to
>    store it into serial EEPROM. Think about MAC as a board id.

If I was to configure such a system, the user is NOT able  to  change
the MAC address.

If you allow to overwrite the "ethaddr" variable this of course  gets
saved together with the other enviroment variables.

If you want to allow the user to  modify  the  hardware  ID  (in  the
SROM), then provide a separate tool for it.

And yes, I do think about the MAC as  a  board  ID.  This  is  why  I
recommend to make it NOT changable by the user.

> It is posible that board dies (it is hit by flash, etc). In that case
> servician comes to replace it and stores the MAC used by dead board to
> new one, not breaking customers setup and to save MAC addresses from
> purchased range.

This is NEW board, so it has a new board ID - obviously. Sorry, but I
feel this is a constructed example, and not a real problem.  You  can
be  lucky that U-Boot provides the flexibility to do such things, but
this is not a free ticket for misuing it. Just assume the  bootloader
does  not  allow  changing the MAC address. This is actually the case
with _most_ boot loaders.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
Never worry about theory as long as  the  machinery  does  what  it's
supposed to do.                                      - R. A. Heinlein

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