The
atw driver supports PCI/CardBus 802.11b wireless adapters based on the ADMtek ADM8211.
The ADM8211 is a bus-mastering 802.11 Media Access Controller (MAC) which is derived from ADMtek's Tulip clones (see
tlp(4)). It supports contention-free traffic (with an 802.11 Point Coordinator), 64/128-bit WEP encryption, and 802.11 power-saving. The ADM8211 integrates an RF3000 baseband processor (BBP) by RF Microdevices.
In a typical application, the ADM8211 is coupled with an RF front-end by RFMD and a Silicon Laboratories Si4126 RF/IF synthesizer.
With the ADM8211, the division of labor between the host and NIC is different than with firmware-based NICs such as
an(4),
awi(4), and
wi(4). The ADM8211 is still responsible for real-time 802.11 functions such as sending ACK/RTS/CTS/ATIM frames, sending beacons, and answering CF polls from the access point, but the host takes responsibility for providing 802.11 functions such as scanning, association, and authentication. The host is also responsible for programming both the BBP and the RF/IF synthesizer.
atw contains incomplete support for the ADM8211's WEP encryption/decryption engine.
atw does not yet support hardware WEP decryption, however, it will use the ADM8211's crypto engine to encrypt transmitted frames. Documentation from ADMtek claims that, in addition to the 4 128-bit shared WEP keys, the ADM8211 will store WEP key pairs for up to 20 peers. The documentation provides no details, hence
atw does not support the 20 key-pairs.
The ADM8211 operates in 802.11 infrastructure mode (with an access point) and in 802.11 ad hoc mode (without an access point) at 1, 2, 5.5, and 11Mbps. ADMtek says that the ADM8211 cannot operate as an access point.
The operating mode is selected using the
ifconfig(8) utility. For more information on configuring this device, see
ifconfig(8) and
ifmedia(4).