> I think you will need to write a small uart handling routine from scratch > (if this is new arch) in order to send the chars to the serial line. > Hi: thanks for your kind help. The location I want the printk works is at init/main.c and I am not sure the kernel serial driver is ready to use at so early time, since I saw the document/serial_port.txt explains that to enable serial driver we need to create dev/ttySx. I will adopt your suggestion. I just see prink function in init/main.c and I just wondering whether I use this printk to output my messages on the UART. appreciate your help, miloody -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ