audio driver and I2C

Hello everybody !

I'm trying to write an audio driver for an audio chip controlled by the I2C bus...
My problem is that I don't have anything related to my audio chip in the /dev/ (audio, dsp, mixer...) directory... and I need it to implement mi ioctl function.
the other problem, is that I don't know how to use the i2c in kernel space...
I know I have to use i2c_master_send() but I d'ont know how to open the I2C and get the appropriate i2c_client structure...

anyone have an idea ?