Tuesday, 02/09/2010

Several new USB devices (especially high-speed wireless WAN stuff, they're expensive anyway) have their MS Windows drivers onboard; when plugged in for the first time they act like a flash storage and start installing the driver from there. After that (and on every consecutive plugging) this driver switches the mode internally, the storage device vanishes (in most cases), and a new device (like an USB modem) shows up. The WWAN gear maker Option calls that feature "ZeroCD (TM)".
Fortunately there are things like human reason, USB sniffing programs and "libusb". It is possible to eavesdrop the communication of the MS Windows driver, to isolate the command or action that does the switching, and to reproduce the same thing with Linux.
USB_ModeSwitch makes the last step considerably easier by taking the important parameters from a configuration file and doing all the initialization and communication stuff. It does NOT check for success afterwards as of now. The right approach would be to consult /proc/bus/usb/devices (or the output of "lsusb") before and after execution to note any changes.