em(4) on FreeBSD is sometimes annoying

Robert Watson rwatson at FreeBSD.org
Fri Aug 1 15:00:27 UTC 2008

On Fri, 1 Aug 2008, Martin wrote:

> I don't remember anymore when I reported it the first time. I think it was 
> around 4.x or something like that. The em(4) bug is still there after years.
> Hasn't anyone really noticed yet that em(4) only appears when you boot 
> FreeBSD with the interface physically attached to a switch for example? If 
> you attach it later, after boot up, the interface won't power up and appear 
> in the interface list (ifconfig)?

The card range supported by the if_em driver is huge, so it wouldn't be 
surprising if this is a hardware bug affecting a relatively narrow line of 
parts.  I've added Jack Vogel to the CC line, as he's the Intel developer 
responsible for maintaining our if_em driver.  I don't promise he can help 
either, but it's worth a try :-).


> Steps to reproduce:
> 1) Switch your PC/laptop off. Really OFF, no reboot.
> 2) Disconnect the em(4) NIC from your switch.
> 3) Boot FreeBSD.
> 4) Plug in the ethernet cable.
> 5) Tataa! All leds at the NIC stay off. You won't be able to use em(4)
> unless you reboot your machine.
> Something is not being initialized properly on em(4) devices, it seems.
> I have had 3 of 3 em(4) NICs so far, where this bug shows up. And it's
> extremely annoying on Thinkpads, when you just want to plug in your
> laptop somewhere.
> --
> Martin

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