printk loglevel

Linux设备驱动第三版第三章：

 

There are eight possible loglevel strings, defined in the header ; we list them in order of decreasing severity:

KERN_EMERG
Used for emergency messages, usually those that precede a crash.

KERN_ALERT
A situation requiring immediate action.

KERN_CRIT
Critical conditions, often related to serious hardware or software failures.

KERN_ERR
Used to report error conditions; device drivers often use KERN_ERR to report hardware difficulties.

KERN_WARNING
Warnings about problematic situations that do not, in themselves, create serious
problems with the system.

KERN_NOTICE
Situations that are normal, but still worthy of note. A number of security-related
conditions are reported at this level.

KERN_INFO
Informational messages. Many drivers print information about the hardware
they find at startup time at this level.

KERN_DEBUG
Used for debugging messages.

Each string (in the macro expansion) represents an integer in angle brackets. Integers range from 0 to 7, with smaller values representing higher priorities.