I have spent a few hours over the last 3 days trying to work out why hostapd 1.0 on a custom built buildroot image wouldn’t work with an Realtek 8192 usb wireless card in AP mode while using the vendor driver. It turns out that this driver comes bundled with an alternative hostapd. The bundled hostapd comes with a new driver named rtl871xdrv, which does not exist in the public version (At least, up to 1.0, AFAICT.) In order to get this to work, we must compile the hostapd supplied using a .config that contains a line that reads like: CONFIG_DRIVER_RTW=y

Then, once built, it should be straight-forward to test and setup an Access Point using your usb-wireless nic. I have used this hostapd configuration to test it:

    interface=wlan0
    #bridge=br0
    driver=rtl871xdrv
    ssid=SampleNetwork
    hw_mode=g
    channel=11
    macaddr_acl=0
    auth_algs=1
    ignore_broadcast_ssid=0
    wpa=3
    wpa_passphrase=password
    wpa_key_mgmt=WPA-PSK
    wpa_pairwise=CCMP
    rsn_pairwise=CCMP

I have also tested it using kvm/qemu’s passthrough and it works well. I am, however, unable to explain why the hostapd that comes with Ubuntu 13.04 seems to work fine. My hunch is that, considering they are using a more upstream kernel than we are (2.6.31.8 here) which contains an the inbox driver for this wireless card and nl80211 which hostapd can speak to natively and does not need to be modified. This is just a hunch, however.