Hello Franz -
as a comment: Whenever I used drivers from a chip manufacturer so far I had a miserable experience. Basic features and most common applications usually work, but thats it. Drivers are usually buggy and unmaintained. Particularly ad-hoc mode support usually is theoretically there but practically broken. I know of no proprietary vendor driver that works properly.
The fact that you are usually bound to a very old version of Linux is telling. I only use / promote chips with decent open-source support. OpenWrt is awesome.
Cheers, Elektra