Does atheros Hal control CSMA?

[Joengmin Hwang]

I am finding the part which control carrier sense (CSMA).
I've checked atheros source code and related 802.11 source code.
But i cannot find it out.

Now i am wondering if it is controlled by HAL.
But since HAL is only provided as binary code, i cannot figure it out.

I would really appreciate if anyone let me know which part is controlling carrier sense.
Is it HAL?

Thanks.