printf vs  printk
==================

printf() is a function in the C Standard Library

printk() is a kernel level function

The printk() is called with one more argument than printf(), like this:

printk(KERN_log_priority "hello world\n");

Here, log_priority is one of the eight values (predefined in linux/kernel.h, similar to /usr/include/sys/syslog.h)

	EMERG, 
	ALERT, 
	CRIT, 
	ERR, 
	WARNING, 
	NOTICE, 
	INFO, 
	DEBUG (in order of decreasing priority).

printk() writes to the kernel buffer, whereas printf() writes on the standard output