I have Debian Lenny installed as both the Dom0 and DomU. The DomU is to provide network printing abilities to Windows clients via Samba.
I actually had a nearly identical setup on a previous production machine. The only difference in that setup was the OS for both Dom0 and DomU were Ubuntu 8.04 LTS.
The printer is an HP Deskjet 5150c with a USB connection. On the previous machine, a new USB PCI card was installed and passed to the DomU utilizing the pciback.hide commands within Grub. Similarly, the USB PCI card address is assigned to the DomU through the Xen configuration file. As a point of clarification, I pass the whole USB PCI card and not individual ports. This is the exact approach I used on the previous production machine.
It appears to be working fine as here are the results of lspci and lsusb from the running DomU:
00:00.0 USB Controller: NEC Corporation USB (rev 43)
00:00.1 USB Controller: NEC Corporation USB (rev 43)
00:00.2 USB Controller: NEC Corporation USB 2.0 (rev 04)
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 003: ID 03f0:6204 Hewlett-Packard DeskJet 5150c
Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
I went through the CUPS installation as normal and it recognized and installed the HP printer.
When I try to print the test page, I receive a kernal panic and a page never comes out. I can recreate the problem to get the exact kernal error message, but it is very cryptic and mainly a series of two digit alpha numeric combinations.
The only way to get the machine working again is a reboot.