Dear list, To read and write to serial ports from Kernel space I would take a look at /proc/ioports to find out the address range of the port I want to use. # cat ioports |grep serial 03f8-03ff : serial Then I would use inb() functions outb() to read and write from I/O registers. But how can I figure it out the address range for usb-serial /dev/ttyUSB0? There is nothing at /proc/ioports. My device uses cypress_m8 and usbserial modules. How bad is using filp_open() to open /dev/ttyUSB0? Thanks, Peter -- Peter Senna Tschudin peter.senna@gmail.com gpg id: 48274C36