Does this work in kernel mode too? I'm writing a kernel module which has to interact with arduino board..
You don't know how to access a serial interface in Linux but you wanna write a kernel module?
Start with a smaller project, build a simple kernel module. Extend it to read files. Extend it to access simple character devices (like /dev/random). If that all works try accessing a complex tty device like the serial interface.
You cannot use functionality of the GNU C library withing the kernel (fopen, fclose and the like), don't use any library at all, use the kernel calls directly. This is really different from userland programming.