Subject: Re: [PATCH] dnet: Dave DNET ethernet controller driver

From: Robert Schwebel <[email-masked]>
Date: Wed, 11 Mar 2009 19:23:37 +0100

On Wed, Mar 11, 2009 at 06:23:36AM -0700, David Miller wrote:
> From: Wolfgang Denk <[email-masked]>
> Date: Wed, 11 Mar 2009 10:09:38 +0100
> 
> > How do you then handle situations where this is impossible? Say, when
> > the firmware cannot write to those registers for example because  the
> > ethernet  controller is not even powered on (to reduce power consump-
> > tion), but will get powered on only in Linux  when  the  driver  gets
> > loaded (i. e. on demand only, not always)?
> 
> That's what NVRAM, CMOS, EEPROM's and other writable long-term
> storage areas are for.
> 
> To be quite honest with you, any ethernet device that doesn't
> have an EEPROM where the chip instance's ethernet address is
> stored is completely broken.

However, it's quite common in embedded systems where eeprom chips cost
money and high quantity projects are cost optimized. So we cannot
neglect reality here. I know almost no ARM board that has a separate
eeprom for the network chip, and especially SoC-integrated MAC units
don't even have hardware interfaces for that.

rsc
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