config USB_SERIAL_QUATECH_USB2 tristate "USB Quatech xSU2-[14]00 USB Serial Driver" depends on USB_SERIAL help Say Y here if you want to use a Quatech USB2.0 to serial adaptor. This driver supports the SSU2-100, DSU2-100, DSU2-400, QSU2-100, QSU2-400, ESU2-400 and ESU2-100 USB2.0 to RS232 / 485 / 422 serial adaptors. Some hardware has an incorrect product string and announces itself as ESU-100 (which uses the serqt driver) even though it is an ESU2-100. Check the label on the bottom of your device. To compile this driver as a module, choose M here: the module will be called quatech_usb2 .