Subject: Re: Ethernet MAC address question

From: Jeff Garzik <[email-masked]>
Date: Mon, 14 Jun 2004 19:34:50 -0400

Don Fry wrote:
> When and/or why would an ethernet driver not use the MAC address from
> the PROM associated with the adapter?
> 
> Since the MAC address can be specified via "ifconfig ethN ether ...."
> why not use the PROM value, and override it later if needed?
> 
> I have received several complaints that the pcnet32 adapter is using
> the 'wrong' MAC address.  By looking back through older kernels, the
> pcnet32 code was changed between November 2001 and February 2002 to
> read the MAC address from PROM, but to use whatever value was read
> from some volatile chip registers, which early chip versions do not
> even initialize.
> 
> It seems to me the driver should always use the PROM address, assuming
> it has one.  What am I missing?

In general, you are correct.

However there are a few cases where some magic platform means loads the 
MAC address into the (volatile) MAC address registers, and that's the 
only source of an accurate MAC address for those people.

	Jeff