root=/dev/nfs on sbc8260

jtm at jtm at
Fri Dec 14 07:25:47 EST 2001

On Thu, Dec 13, 2001 at 10:41:40AM -0500, Andrew Dixon wrote:
> Here is something very strange.  In PPCBoot I set the ethernet address
> to 00:a0:1e:90:15:55.
> ....
> Now, as I watch Linux try to come up I see the following:
> ....
> Has anyone else seen this before?

In the ethernet driver for the FCC, it changes the MAC address based on
the FCC number.h

In a standard 2.4.4 kernel, arch/ppc/8260_io/fcc_enet.c is the
following code (around line 1315):
       /* Set Ethernet station address.
         * This is supplied in the board information structure, so we
         * copy that into the controller.
         * So, far we have only been given one Ethernet address. We make
         * it unique by setting a few bits in the upper byte of the
         * non-static part of the address.
        eap = (unsigned char *)&(ep->fen_paddrh);
        for (i=5; i>=0; i--) {
                if (i == 3) {
                        dev->dev_addr[i] = bd->bi_enetaddr[i];
                        dev->dev_addr[i] |= (1 << (7 - fip->fc_fccnum));
                        *eap++ = dev->dev_addr[i];
                else {
                        *eap++ = dev->dev_addr[i] = bd->bi_enetaddr[i];

You can here see that the ethernet port's MAC address is dependent on
the fcc number.

Jay Monkman	    The truth knocks on the door and you say "Go away, I'm
monkman at    looking for the truth," and so it goes away. Puzzling.
		     - from _Zen_and_the_Art_of_Motorcycle_Maintenance_

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