ATH(4) OpenBSD Programmer's Manual ATH(4)NAMEath - Atheros IEEE 802.11a/b/g wireless network device with GPIO
ath* at pci? dev ? function ?
ath* at cardbus? dev ? function ?
gpio* at ath?
The ath driver provides support for wireless network devices based on the
Atheros AR5210, AR5211, and AR5212 chips.
All host/device interaction is via DMA. The ath driver encapsulates all
IP and ARP traffic as 802.11 frames, though it can receive either 802.11
or 802.3 frames. Transmit speed and operating mode is selectable and
depends on the specific chipset.
Support for the various devices is as follows:
AR5210 These devices support 802.11a operation with transmit speeds of 6
Mbps, 9 Mbps, 12 Mbps, 18 Mbps, 24 Mbps, 36 Mbps, 48 Mbps, and 54
AR5211 These devices support 802.11a and 802.11b operation with transmit
speeds as above for 802.11a and 1Mbps, 2Mbps, 5.5 Mbps, and
11Mbps for 802.11b operation.
AR5212 These devices support 802.11a, 802.11b, and 802.11g operation
with transmit speeds as above for 802.11a, 802.11b, and 802.11g
operation (802.11g speeds are the same as for 802.11a speeds).
All chips also support an Atheros Turbo Mode (TM) that operates in the
802.11a frequency range with 2x the transmit speeds. (This mode is,
however, only interoperable with other Atheros-based devices.)
The actual transmit speed used is dependent on signal quality and the
``rate control'' algorithm employed by the driver.
These are the modes the ath driver can operate in:
BSS mode Also known as infrastructure mode, this is used when
associating with an access point, through which all
traffic passes. This mode is the default.
IBSS mode Also known as IEEE ad-hoc mode or peer-to-peer mode. This
is the standardized method of operating without an access
point. Stations associate with a service set. However,
actual connections between stations are peer-to-peer.
Host AP In this mode the adapter acts as an access point (base
station) for other cards.
monitor mode In this mode the driver is able to receive packets without
associating with an access point. This disables the
internal receive filter and enables the card to capture
packets from networks which it wouldn't normally have
access to, or to scan for access points.
The ath driver can be configured to use Wired Equivalent Privacy (WEP) or
Wi-Fi Protected Access (WPA-PSK and WPA2-PSK). WPA is the de facto
encryption standard for wireless networks. It is strongly recommended
that WEP not be used as the sole mechanism to secure wireless
communication, due to serious weaknesses in it.
AR5211 and AR5212 support the AES, TKIP, and Michael cryptographic
operations required for WPA in hardware but at this time the driver does
not support them.
The ath driver can be configured at runtime with ifconfig(8) or on boot
Devices supported by the ath driver come in either CardBus or Mini PCI
packages. Wireless cards in CardBus slots may be inserted and ejected on
The following cards are among those supported by the ath driver:
Card Chip Bus Standard
3Com 3CRPAG175 AR5212 CardBus a/b/g
Cisco AIR-CB21AG AR5212 CardBus a/b/g
D-Link DWL-A650 AR5210 CardBus a
D-Link DWL-AB650 AR5211 CardBus a/b
D-Link DWL-A520 AR5210 PCI a
Elecom LD-WL54 AR5211 CardBus a
IBM 11ABG WL LAN AR5212 Mini PCI
Linksys WPC51AB AR5211 CardBus a/b
Netgear WAB501 AR5211 CardBus a/b
Planet WL-3560 AR5211 CardBus a/b/g
Proxim Skyline 4030
AR5210 CardBus a
Proxim Skyline 4032
AR5210 PCI a
Senao NL-5354MP AR5212 Mini PCI
SMC SMC2735W AR5210 CardBus a
Sony PCWA-C500 AR5210 CardBus a
Wistron CM9 AR5212 Mini PCI
An up to date list can be found at
The following hostname.if(5) example configures ath0 to join whatever
network is available on boot, using WEP key ``0x1deadbeef1'', channel 11,
obtaining an IP address using DHCP:
dhcp NONE NONE NONE nwkey 0x1deadbeef1 chan 11
The following hostname.if(5) example creates a host-based access point on
inet 192.168.1.1 255.255.255.0 NONE media autoselect \
mediaopt hostap nwid my_net chan 11
Configure ath0 to join network ``my_net'' using WPA with passphrase
# ifconfig ath0 nwid my_net wpakey my_passphrase
Join an existing BSS network, ``my_net'':
# ifconfig ath0 192.168.1.1 netmask 0xffffff00 nwid my_net
ath%d: unable to attach hardware; HAL status %u The Hardware Access
Layer was unable to configure the hardware as requested. The status code
is explained in the HAL include file sys/dev/ic/ar5xxx.h.
ath%d: failed to allocate descriptors: %d The driver was unable to
allocate contiguous memory for the transmit and receive descriptors.
This usually indicates system memory is scarce and/or fragmented.
ath%d: unable to setup a data xmit queue! The request to the HAL to set
up the transmit queue for normal data frames failed. This should not
ath%d: unable to setup a beacon xmit queue! The request to the HAL to
set up the transmit queue for 802.11 beacon frames failed. This should
ath%d: hardware error; resetting An unrecoverable error in the hardware
occurred. Errors of this sort include unrecoverable DMA errors. The
driver will reset the hardware and continue.
ath%d: rx FIFO overrun; resetting The receive FIFO in the hardware
overflowed before the data could be transferred to the host. This
typically occurs because the hardware ran short of receive descriptors
and had no place to transfer received data. The driver will reset the
hardware and continue.
ath%d: unable to reset hardware; hal status %u The Hardware Access Layer
was unable to reset the hardware as requested. The status code is
explained in the HAL include file /sys/dev/ic/ar5xxx.h. This should not
ath%d: unable to initialize the key cache The driver was unable to
initialize the hardware key cache. This should not happen.
ath%d: unable to start recv logic The driver was unable to restart frame
reception. This should not happen.
ath%d: device timeout A frame dispatched to the hardware for
transmission did not complete in time. The driver will reset the
hardware and continue. This should not happen.
ath%d: bogus xmit rate 0x%x An invalid transmit rate was specified for
an outgoing frame. The frame is discarded. This should not happen.
ath%d: ath_chan_set: unable to reset channel %u (%u MHz) The Hardware
Access Layer was unable to reset the hardware when switching channels
during scanning. This should not happen.
ath%d: unable to allocate channel table The driver was unable to
allocate memory for the table used to hold the set of available channels.
ath%d: unable to collect channel list from hal A problem occurred while
querying the HAL to find the set of available channels for the device.
This should not happen.
ath%d: failed to enable memory mapping The driver was unable to enable
memory-mapped I/O to the PCI device registers. This should not happen.
ath%d: failed to enable bus mastering The driver was unable to enable
the device as a PCI bus master for doing DMA. This should not happen.
ath%d: cannot map register space The driver was unable to map the device
registers into the host address space. This should not happen.
ath%d: could not map interrupt The driver was unable to allocate an IRQ
for the device interrupt. This should not happen.
ath%d: could not establish interrupt The driver was unable to install
the device interrupt handler. This should not happen.
SEE ALSOarp(4), cardbus(4), gpio(4), ifmedia(4), intro(4), netintro(4), pci(4),
hostname.if(5), gpioctl(8), hostapd(8), ifconfig(8)HISTORY
The ath device driver first appeared in FreeBSD 5.2 using a binary-only
HAL module which was ported to NetBSD 2.0. The driver using a free HAL-
replacement first appeared in OpenBSD 3.7.
The ath driver was written by Sam Leffler, and was ported to OpenBSD by
Reyk Floeter <email@example.com> who also wrote a free replacement of the
Different regulatory domains may not be able to communicate with each
other with 802.11a as different regulatory domains do not necessarily
have overlapping channels.
Host AP mode doesn't support power saving. Clients attempting to use
power saving mode may experience significant packet loss (disabling power
saving on the client will fix this).
Performance in lossy environments is suboptimal. The algorithm used to
select the rate for transmitted packets is very simplistic. There is no
software retransmit; only hardware retransmit is used. Contributors are
encouraged to replace the existing rate control algorithm with a better
The driver does not fully enable power-save operation of the chip;
consequently power use is suboptimal.
OpenBSD 4.9 November 1, 2010 OpenBSD 4.9