how to configure hostap in ad hoc mode

[Do Thi Phuong Thao]

Hi all,
I have card wireless 3COM 3CRPAG175. I want to run hostapd in ad hoc mode but there are some problems. Can some one show me the way to configure hostap in ad hoc mode? pls. Thanks alot.

* if ath0 is in ad hoc mode and i run: 
#hostapd /etc/hostapd.conf
Configuration file: /etc/hostapd.conf
ioctl[SIOCSIWMODE]: invalid argument
Could not set interface to master mode!
madwifi driver initialization failed. 

*if ath0 is in master mode (AP) and i run: 
 #hostapd /etc/hostapd.conf
there isn't any error. But
#iwconfig ath0 mode ad-hoc
Error for wireless request "Set Mode" (8B06):
Set failed on device ath0; Invalid argument.
 	      
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