Pluggable frame buffer devices

Hi,

I've added support for USB display link adapters to FreeBSD-11-current, 
but the kernel panics once "vt_fb_attach(info)" is called from 
"fbd_register(struct fb_info* info)" when the USB device is plugged or 
udl.ko is loaded. Is this a known issue?

REF: https://svnweb.freebsd.org/base/head/sys/dev/usb/video/udl.c

--HPS