Is writing usb devices as files (via /dev/ugen*) supported in FreeBSD?

[Torfinn Ingolfsen]

Hello,
Question: is writing to the device file (/dev/ugenX) with normal file calls supposed to work in FreeBSD?
(as in "everything is a file" in unix-like operating systems)

Background: I recently got a usb label printer for cheap: a Dymo LabelManager PnP[1]. I found the dymoprint[2] Python script, which works fairly well on Linux.
It works (AFAICT) by reading / writing the usb device as a regular file, via the device file.
You have to use usb_modeswitch[3] on the printer first, of course.

Since we have all tools available on FreeBSD, I tried the setup on my FreeBSD workstation, which currently runs FreeBSD 9.3-stable:
tingo at kg-core1$ uname -a
FreeBSD kg-core1.kg4.no 9.3-STABLE FreeBSD 9.3-STABLE #0 r273918: Fri Oct 31 22:52:44 CET 2014     root at kg-core1.kg4.no:/usr/obj/usr/src/sys/GENERIC  amd64

The detection code in the dymoprint script doesn't work on FreeBSD, but setting the correct device via DEV_NODE in the script works:
tingo at kg-core1$ grep ^DEV_NODE dymoprint2
DEV_NODE       = "/dev/ugen3.4"

But when I run the script I just get an IO error:
root at kg-core1# python dymoprint2 test
Traceback (most recent call last):
  File "dymoprint2", line 313, in <module>
    main()
  File "dymoprint2", line 309, in main
    lm.printLabel(labelmatrix, dottab)
  File "dymoprint2", line 183, in printLabel
    response = self.sendCommand()
  File "dymoprint2", line 80, in sendCommand
    responseBin = self.dev.read(8)
IOError: [Errno 5] Input/output error


References:
1) http://global.dymo.com/ieIE/Products/LabelManager_PnP.html
2) http://sbronner.com/dymoprint/
3) http://www.draisberghof.de/usb_modeswitch/
-- 
Torfinn Ingolfsen <torfinn.ingolfsen at getmail.no>