Sepherosa Ziehau has updated the em driver to sync with FreeBSD-current, among other things, adds support for the Intel PRO/1000 GT and 82546G. He’s also added DEVICE_POLLING to the GENERIC kernel. What’s it do? I don’t know!
Update: Now I know.
A running description of activity related to DragonFly BSD.
Best guess is that the kernel will actively check on the status of a device in order to make it work when it otherwise wouldn’t due to the current “confused” state of the interrupt routing code.