Unknown symbol usb_register_driver

Hi

I am using Linux-2.6.31-14 based on Ubuntu karmic. I am developing
a proprietary usb driver and was doing my study . I have hit upon a problem,
when i insert my driver using lsmod, i get an error

*Unknown symbol usb_register_driver*
*Unknown symbol usb_deregister*

I have used these function in my init and exit.

I searched through the Linux source code 2.6.35 and 2.6.31. I find that
these routines are present but has not been used in even a single driver.

My questions
1. Are these some obsolete technique of registering the drivers. If yes then
what is the correct method.
2. Are there any code which i have to include before compiling the kernel
itself.
3. Are these functions part of any modules which i have to insert using
modprobe etc technique

-- 
Regards,

Prajosh Premdas
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