printk 打印级别

#define KERN_EMERG        "<0>" /* system is unusable */

#define KERN_ALERT         "<1>" /* action must be taken immediately */

#define KERN_CRIT            "<2>" /* critical conditions */

#define KERN_ERR             "<3>" /* error conditions */

#define KERN_WARNING   "<4>" /* warning conditions */

#define KERN_NOTICE       "<5>" /* normal but significant condition */

#define KERN_INFO            "<6>" /* informational */

#define KERN_DEBUG       "<7>" /* debug-level messages */

printk(KERN_EMERG  “WelCome”)