1. Download compat wireless packet.

http://www.orbit-lab.org/kernel/compat-wireless-2.6-stable/v2.6.37/compat-wireless-2.6.37-4.tar.bz2

2. Untar  compat-wireless-2.6.37-4.tar.bz2  archive.

tar xvjf compat-wireless-2.6.37-4.tar.bz2

3. Select the driver you want to compile.

cd compat-wireless-2.6.37-4/

then

./scripts/driver-select
shows all available drivers (from compat-wireless packet)

./scripts/driver-select  ath5k
selects ath5k to compile

./scripts/driver-select  ath9k
selects ath9k to compile

note : if you don't select any driver
in the next step, all drivers will be compiled.

4. Build and install driver

make

sudo make install

now you can either restart your pc or use the command

sudo modprobe ath5k
or
sudo modprobe ath9k

to load the driver

but if you do this you must first have unloaded other wireless modules if there are any( sudo modprobe -r ath_pci )

sudo make unload to unload all: wireless, bluetooth and ethernet modules
sudo make wlunload to unload wireless modules
sudo make btunload to unload bluetooth modules

Blacklisting ath_pci and ath5k may be needed

sudo gedit /etc/modprobe.d/blacklist

echo "blacklist ath9k" >> /etc/modprobe.d/blacklist

echo "blacklist ath5k" >> /etc/modprobe.d/blacklist

Restart to check the newly installed modules.

5. If you want to uninstall or unload you can run.

sudo make uninstall

sudo make unload

6. If you would like to enable MadWifi at a later time and disable ath5k you can run:

sudo athload madwifi

To revert back to ath5k you can run:

sudo athload ath5k

7. If you want to hack the driver  , you have to change the above files:

here :
/home/ioannis/ath5k-test/compat-wireless-2.6.37-4/drivers/net/wireless 
are all wireless drivers

and here :
/home/ioannis/ath5k-test/compat-wireless-2.6.37-4/drivers/net/wireless/ath
are atheros drivers (ath5k and ath9k )

and here :
/home/ioannis/ath5k-test/compat-wireless-2.6.37-4/net/mac80211
are mac80211 files (Mac80211 is the new wireless stack of the Linux kernel)

then you must compile again the driver.

source:
http://wireless.kernel.org/en/users/Download

HOSTAPD configure

http://rt2x00.serialmonkey.com/wiki/index.php/AP-mode_Howto

http://wiki.openwrt.org/doc/howto/wireless.utilities

http://processors.wiki.ti.com/index.php/OMAP_Wireless_Connectivity_NLCP_WLAN_IW_commands