Important functions are listed here.

Print kernel message

The printk() function is defined in kernel/printk/printk.c. The pr_xxx() funcitons are defined in include/linux/printk.h.

printk()

Print a kernel message. The base function called by pr_xxx functions.

pr_emerg()

Print a kernel message with emergency log level.

pr_alert()

Print a kernel message with alert log level.

pr_crit()

Print a kernel message with critical log level.

pr_err()

Print a kernel message with error log level.

pr_warning()

Print a kernel message with warning log level.

pr_notice()

Print a kernel message with notice log level.

pr_info()

Print a kernel message with information log level.

Bit operation

The bit operation functions are defined in include/asm-generic/bitops/atomic.h.

set_bit()

Atomically set a bit in memory.

clear_bit()

Atomically clear a bit in memory.