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