1. print

printk(): never

pr_debug(): always good

dev_dbg(): prefered when you have a struct device object

netdev_dbg(): prefered when you have a struct netdevice object

[something]_dbg(): prefered when you have a that something object

2. using file system proc/ memory large file or sequence file

3. using Ioctrl to get/set specific data

Below shall enable the kernel debug.

4. gdb list command to idenfiy the line of oops

5. addr2line command to identify the line of oops

linux kernel driver debug