This issue, where a USB device is detected, but no USB port assigned has taken me a lot of effort to solve on several occasions, because I forgot the fix each time, so hopefully this post might help you!
In short if you connect a ‘new’ USB device and it does not ‘work’, but dmesg reports something like below and the device number increments on every dis/reconnect:
usb 4-2: new full speed USB device number 11 using uhci_hcd
The issue is that no USB port has been assigned, as seen below in this successful connection:
usb 4-2: new full speed USB device number 12 using uhci_hcd
cdc_acm 4-2:1.0: ttyACM0: USB ACM device
The following fix has worked for me on three, maybe four, systems:
sudo modprobe cdc_acm
The systems it definitely fixed were the Dangerous Prototypes OLS, a USnooBie and just this week, an Arduino UNO v2.0. Plus it probably fixed a Dangerous Prototypes BusBlaster, but my notes don’t document and it almost certainly would have fixed the very long saga I had with the Dangerous Prototypes IRToy, but it went a different, painful process, that I won’t be able to reproduce, but the root issue seemed the same.
While three of these systems are all from Dangerous Prototypes, ALL five have a different hardware USB implementation! The Arduino and Dangerous Prototypes devices are also all very popular.
Two references that helped were 1 and 2. The second, Gentoo link, talks about modprobe cdc_acm and interestingly modprobe ftdi_sio, which I have not used, but am trying to burn into my brain for the next issue I have. I must have used other sites – but apologies to them as I forgot to record the sources 🙁
Possibly relevant background information:
I only use the one Ubuntu laptop, so have not run into this on any other systems! The build started with 10.10 and took all upgrades up to 11.10. These devices all worked on Windows XP Pro, with only a couple of minor issues.
I have successfully used lots of other devices on the same Ubuntu laptop, including an Arduino Deumilanove, a DP BusPirate, a DP USB LCD Backpack, and three different types of USB to TTL (FTDI) convertors.
Highly relevant background information = I break stuff – lots of stuff, just by touch and sometimes it seems just by looking.