ATW(4)

NAME
atw - ADMtek ADM8211 802.11 wireless network driver

SYNOPSIS
atw* at cardbus? function ?
atw* at pci? dev ? function ?

DESCRIPTION
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).

HARDWARE
Cards supported by the atw driver include:

D-Link DWL-650 Rev. ?? CardBus card
D-Link DWL-520 Rev. C1 PCI card
LanReady WP2000 PCI card
TrendNet TEW-221PC CardBus card
Xterasys XN2511B PCI card

DIAGNOSTICS

atw0: failed to tune channel %d The driver failed to tune the radio to a new channel. The radio remains tuned to the old channel.

atw0: atw_si4136_write wrote %08x, SYNCTL still busy The driver waited 100ms without seeing an indication that the ADM8211 had finished writing a register on the Si4126 RF/IF synthesizer.

atw0: device timeout The ADM8211 failed to generate an interrupt to acknowledge a transmit command.

SEE ALSO
arp(4), cardbus(4), ifmedia(4), netintro(4), pci(4), ifconfig(8) ADMtek, http://www.admtek.com.tw. Silicon Laboratories, http://www.silabs.com. RF Microdevicdes, http://www.rfmd.com.

HISTORY
The atw device driver first appeared in NetBSD 2.0.

AUTHORS
-nosplit The atw driver was written by David Young <dyoung@NetBSD.org>. For features which the ADM8211 has in common with the DECchip 21x4x, code was liberally borrowed from tlp(4) by Jason Thorpe <thorpej@NetBSD.org>.

BUGS
The author does not fully understand what processing the duration fields for the PLCP header and the 802.11 header undergo before they are applied to a transmitted frame. If the duration fields in transmitted frames are incorrect, the performance of your network may suffer.

The driver does not provide rate control when the media type is set to autoselect.

The driver lets you change to hostap mode, but it does not work and it probably never will.

The driver will sometimes complain that it cannot re-tune the radio because the transmit process has not gone idle. The author is investigating.

Many features are still missing, especially WEP decryption and 802.11 power-saving.

The ad hoc mode has not been rigorously tested. IBSSs with the same SSID may not coalesce, but this should not matter for most applications.

The driver is untested in the ad-hoc demo mode of Lucent WaveLAN cards.

The ADM8211 supports 802.11 power-saving, however, atw does not support it yet. For time-bounded service, the ADM8211 will interoperate with an access point which implements the 802.11 Point Coordination Function, however, this is also not supported.

Combinations of an ADM8211 with either an Intersil or a Marvell RF front-end are not supported.