C-Media CM6535 firmware

hello,
I am designing a recoring device based on CM6535 from C-Media.

I purchased the IC from:
CM6535 - CM6535 USB 2.0 Audio Chip with Tri-Colors PWM LED driver

after making a small test PCB - i connected it to my linux device, and it does get detected by lsusb commmand, but no audio i/o avaliable (checked using aplay -L).

I have another dev board for a similar IC CM6510 - and it does work well.

my thughts are that a firmware is needed, but i have no idea how to even begin.

can anyone please direct me to the right direction?

thanks allot.