Find tutorial write driver for BeagleBoard rev C4

Dear all,

I have a BB rev C4 running Angstrong demo image from
I connect my BB to my laptop. From my laptop, I using ccs and can remote BB by Remote System Explorer and debug code via gdbserver. Now I can already code some simple code, run and debug in BB.
Next, I’ll try to write some driver for BB (like audio driver). Please show me some link or tutorial from that I can follow. I’m new with write driver, so please show me a guide step by step.

Thank you and best regard,

Nguyen Dung