atw - ADMtek ADM8211 802.11 wireless network driver
atw* at cardbus? function ?
atw* at pci? dev ? function ?
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 DEC/Intel 21143 clones (see dc(4)).
contention-free traffic (with an 802.11 Point Coordinator),
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
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),
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
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
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
The ADM8211 operates in 802.11 infrastructure mode (with an
and in 802.11 ad hoc mode (without an access point) at 1, 2,
11Mbps. ADMtek says that the ADM8211 cannot operate as an
The operating mode is selected using the ifconfig(8) utility. For more
information on configuring this device, see ifconfig(8) and
The atw driver supports PCI and Cardbus cards using revision
0x15 of the ADM8211 (aka ADM8211A). This includes:
3Com OfficeConnect 3CRSHPW796 Cardbus card
Belkin F5D6001 PCI card
Blitz NetWave Point Cardbus card
D-Link DWL-650 Rev. L1 Cardbus card
D-Link DWL-520 Rev. C1 PCI card
LanReady WP2000 PCI card
TrendNet TEW-221PC Cardbus card
Xterasys XN2511B PCI card
The atw driver does not yet support cards using revision
or 0x30 (ADM8211C). This includes:
SMC 2635W Cardbus card
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
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.
an(4), arp(4), cardbus(4), ifmedia(4), netintro(4), pci(4),
Silicon Laboratories, http://www.silabs.com.
RF Micro Devices, http://www.rfmd.com.
The atw device driver first appeared in OpenBSD 3.6.
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 the NetBSD tlp driver by
Jason Thorpe <thorpej@NetBSD.org>.
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
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
Many features are still missing, especially WEP decryption
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
The ADM8211 supports 802.11 power-saving, however, atw does
it yet. For time-bounded service, the ADM8211 will interoperate with an
access point which implements the 802.11 Point Coordination
however, this is also not supported.
Combinations of an ADM8211 with either an Intersil or a Marvell RF frontend
are not supported.
OpenBSD 3.6 June 5, 2004
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