Date: Fri, 8 Jun 2007 21:58:59 +0200 (CEST) From: =?iso-8859-1?Q?Bj=F6rn_K=F6nig?= <bkoenig@alpha-tierchen.de> To: "M. Warner Losh" <imp@bsdimp.com> Cc: arm@freebsd.org Subject: Re: if_ate handles the bytes of the MAC address in a "wrong" order Message-ID: <54751.2001:6f8:101e:0:20e:cff:fe6d:6adb.1181332739.squirrel@webmail.alpha-tierchen.de> In-Reply-To: <20070608.120902.-399284744.imp@bsdimp.com> References: <53385.2001:6f8:101e:0:20e:cff:fe6d:6adb.1181314300.squirrel@webmail.alpha-tierchen.de> <20070608.120902.-399284744.imp@bsdimp.com>
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M. Warner Losh wrote:
> We use the following code:
> low = RD4(sc, ETH_SA1L);
> high = RD4(sc, ETH_SA1H);
> if ((low | (high & 0xffff)) == 0)
> return (ENXIO);
> eaddr[0] = (high >> 8) & 0xff;
> eaddr[1] = high & 0xff;
> eaddr[2] = (low >> 24) & 0xff;
> eaddr[3] = (low >> 16) & 0xff;
> eaddr[4] = (low >> 8) & 0xff;
> eaddr[5] = low & 0xff;
>
> which does look like it is wrong, based on what the text says.
These are the register contents during execution of U-Boot:
U-Boot> md fffbc098 8
fffbc098: 00000000 00000000 3ac25000 000051b4 .........P.:.Q..
fffbc0a8: 00000000 00000000 00000000 00000000 ................
ETH_SA2L = 3ac25000
ETH_SA2H = 000051b4
Our code makes the address 51:b4:3a:c2:50:00. The Linux code looks like this
addr[0] = (lo & 0xff);
addr[1] = (lo & 0xff00) >> 8;
addr[2] = (lo & 0xff0000) >> 16;
addr[3] = (lo & 0xff000000) >> 24;
addr[4] = (hi & 0xff);
addr[5] = (hi & 0xff00) >> 8;
and we would get the MAC address 00:50:c2:3a:b4:51. It may be important
that Linux makes a case differentiation because there is at least one boot
loader out there that stores the MAC address exactly the other way round:
addr[0] = (hi & 0xff00) >> 8;
addr[1] = (hi & 0xff);
addr[2] = (lo & 0xff000000) >> 24;
addr[3] = (lo & 0xff0000) >> 16;
addr[4] = (lo & 0xff00) >> 8;
addr[5] = (lo & 0xff);
with the comment "The CSB337 bootloader stores the MAC the wrong-way around."
The code is from linux-2.6.21/drivers/net/arm/at91_ether.c line 385ff.
Regards
nröjB
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