get usb device descriptor through ioctl?

[thomas nivelet <lugarbleiz%gmail.com@localhost>]

>if you reboot, press a key to drop into the boot(8) menu and enter "boot
>-c", that will get you to the userconf(4) menu - disable the umodem driver
>and continue the boot, you should find that the device will connect
>instead as ugen(4)

That's work, I can filter dfu device but as you say it's very painful,
and I can't imagine giving people the obligation to reboot each time
they want to use the software I'm doing, so I think I need to find why
my system crash while opening dtyU* and ttyU*...