Determining eepro100's negotitated mode

[Donald Becker]

On Thu, 29 Apr 1999, Andrew M. Kuchling wrote:

> I'm trying to figure out if an Intel eepro100 card is coming up in 10-
> or 100-baseT, and full or half-duplex.  However, I can't figure out
> how to read the output of eepro100-diag or mii-diag to determine the
> card's current mode; the Ethernet-HOWTO is silent on this point, and
> the CESDIS eepro100 page isn't clear on how to do this.  (If I get an
> answer, I'll write up a description for that page.)

> eepro100-diag.c:v0.07 2/25/98 Donald Becker (becker@cesdis.gsfc.nasa.gov)
> Index #1: Found a Intel 82557 EtherExpressPro100B adapter at 0x1820.
>  MII PHY #1 transceiver registers:
>   3000 7829 02a8 0150 05e1 41e1 0003 ffff
>   ffff ffff ffff ffff ffff ffff ffff ffff
>   0203 0000 0001 0000 0000 0000 0000 0000
>   0000 0000 0000 0000 ffff ffff ffff ffff.
...
>  Basic mode status register 0x782d ... 782d.
>    Link status: established.
>    Capable of  100baseTx-FD 100baseTx 10baseT-FD 10baseT.
>    Able to perform Auto-negotiation, negotiation complete.
>  I'm advertising 05e1: Flow-control 100baseTx-FD 100baseTx 10baseT-FD 10baseT
>  Link partner capability is 41e1: 100baseTx-FD 100baseTx 10baseT-FD 10baseT.

The negotiated ability is the highest common mode.  In this case it's
100baseTx-FD.

Details of how this occurs is in
  http://cesdis.gsfc.nasa.gov/linux/misc/NWay.html

> 	On a related note, "mii-diag -A link-type" changes the link
> capabilities being advertised; does that actually change the current
> setting of the card?  If not, is it possible to change the
> transceiver's mode after boot-up, and how is it done?

Yes, that option changes the advertised capabilities.
The 'mii-diag' program always restarts negotiation after changing the
capabilities, while the 'eepro100-diag' does not (!).
Thus you should use the 'mii-diag' program to change the setting, unless you
are testing some usual aspect of your network.

[[ Implication: using 'eepro100-diag -A 10baseT-FD' will leave the current
network link setting as-is, but will change the negotiated link when the
cable is disconnected.  Using 'mii-diag -A 10baseT-FD' will immediately
change the link setting, stopping traffic for one to three seconds while
doing so. ]]


Donald Becker					  becker@cesdis.gsfc.nasa.gov
USRA-CESDIS, Center of Excellence in Space Data and Information Sciences.
Code 930.5, Goddard Space Flight Center,  Greenbelt, MD.  20771
301-286-0882	     http://cesdis.gsfc.nasa.gov/people/becker/whoiam.html