Solution:

Duplicate all the variant for all eight ports and assign them individually to each port, that might achieve your goal. For example, int buf_ptr,p; => int buf_ptr1, p1, buf_ptr2, p2, buf_ptr3, p3, buf_ptr4, p4; => int buf_ptr5, p5, buf_ptr6, p6, buf_ptr7, p7, buf_ptr8, p8; p = port_no[port]; => p1 = port_no[1]; => p2 = port_no[2]; => p3 = port_no[3]; => p4 = port_no[4]; => p5 = port_no[5]; => p6 = port_no[6]; => p7 = port_no[7]; => p8 = port_no[8]; . . . . . . sio_open(n); => sio_open(1); => sio_open(2); => sio_open(3); => sio_open(4); => sio_open(5); => sio_open(6); => sio_open(7); => sio_open(8); . . . . . . Then, user can make all the eight ports under control.