current state of default CCA mode?

I was wondering what the current state of the default CCA mode is in
compat-wireless and if it's consistent across the various drivers
(i.e., ath9k, b43, wl12xx, etc)?  Is the default mode shifting from
mode 1 to mode 2?

Also, if anyone has any intuition of what is happening outside of
compat-wireless in terms of the CCA mode, I would really appreciate
it.

Thanks!

- George