Driver for WP7607 module

Hi all,
Currently I writing new driver for wp7607 base on GobiSerial and qcserial , in my driver I have only defined the init(), exit() and probe() functions but I can still use the AT command with just such a simple driver. I don’t know how AT command can work with just the above 3 functions.
Is usbserial(core) driver doing that job?.
Thank for your response!!!