[argyllcms] USB problems

I'm trying to use argyll version 0.60 (as installed from the debian repository). It doesn't seem to be seeing the USB device at all. I think a bit more information about what name(s) the code looks at would be useful. I have no clue how to troubleshoot because I don't know what is supposed to happen. 
I added

# DTP94
SYSFS{idVendor}=="0765", SYSFS{idProduct}=="d094", GROUP="plugdev"
to my udev rules and restarted udev but that didn't seem to make a difference. I looked around but couldn't find a device name that was obviously associated with the device. If I had any clue what was supposed to happen I might be able to fix it, but I don't, so I'm stuck. What device names does argyll look for? If I look in /proc/bus/usb/devices I do see that the device is present and it has the right vendor and product ids: 

T:  Bus=04 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  4 Spd=1.5 MxCh= 0
D:  Ver= 2.00 Cls=ff(vend.) Sub=ff Prot=ff MxPS= 8 #Cfgs=  1
P:  Vendor=0765 ProdID=d094 Rev= 0.00
S:  Manufacturer=X-Rite
S:  Product=X-Rite DTP94
S:  SerialNumber=009190
C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr= 20mA
I:* If#= 0 Alt= 0 #EPs= 2 Cls=ff(vend.) Sub=ff Prot=ff Driver=(none)
E:  Ad=81(I) Atr=03(Int.) MxPS=   8 Ivl=10ms
E:  Ad=02(O) Atr=03(Int.) MxPS=   8 Ivl=10ms
But if I run dispcal it gives only /dev/ttyS? as options, which doesn't seem right. (I tried them all anyway and none worked.) 
adrian> dispcal --
Calibrate a Display, Version 0.60(beta)
Author: Graeme W. Gill, licensed under the GPL
Diagnostic: Usage requested
usage: dispcal [options] outfile
-v               Verbose mode
-display displayname Choose X11 display name
-d n                 Choose the display from the following list (default 1)
   1 = ' at 0, 0, width 1680, height 1050'
-c listno            Set communication port from the following list (default 1)
   1 = '/dev/ttyS0'
   2 = '/dev/ttyS1'
   3 = '/dev/ttyS2'
   4 = '/dev/ttyS3'

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