USS720 driver

The USS720 is a USB to Parallel port chip made by Lucent that normally acts like a USB Printer Class device. Indeed you can use a USS720 based bridge and a parallel port printer with the USB Printer driver, (see above). However there is also a mode (known as register mode) which makes the USS720 look like normal parallel port hardware. This driver makes use of that mode.

If you have the opportunity, look at /proc/sys/dev/parport before you load the module or reboot with a kernel with USS720 enabled. You should note the number of parallel ports you have - typically one, under /proc/sys/dev/parport/parport0. After you put USS720 support into your kernel, you should have another port (perhaps /proc/sys/dev/parport1). If you look at the appropriate hardware entry, you should see something like the following:

[bradh@rachel bradh]$ more /proc/sys/dev/parport/parport1/hardware
base:   0x0
irq:    none
dma:    none

Every distribution should have device node entries for parallel ports - typically /dev/lpX or /dev/parX, where the X is some number. If you need to create them, parallel ports device nodes use character major number 6.

You should now be able to use the USS720 for anything that you would normally need a parallel port for, except that certain timing sensitive applications may not work, since the emulation is rather slow. As for a real USB printer, I suggest use of automated tools to generate a /etc/printcap entry if you are connecting up a printer.

If you didn't get to select USS720 support at the configuration stage, you need to turn on Parallel port support support (under General setup if using menuconfig).