ath — Atheros IEEE
802.11a/b/g wireless network device with GPIO
ath* at pci? dev ? function ?
ath* at cardbus? dev ? function ?
gpio* at ath?
ath driver provides support for
wireless network devices based on the Atheros AR5210, AR5211, and AR5212
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
Support for the various devices is as follows:
- 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 Mbps.
- 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
- 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).
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
- 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
- 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.
ath driver can be configured to use
Wired Equivalent Privacy (WEP) or Wi-Fi Protected Access (WPA-PSK and
WPA2-PSK). WPA is the current 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
In BSS mode, the driver supports powersave mode, which can be
ath driver can be configured at
runtime with ifconfig(8) or
on boot with
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 fly.
The following cards are among those supported by the
|IBM 11ABG WL LAN
|Proxim Skyline 4030
|Proxim Skyline 4032
The following example scans for available networks:
# ifconfig ath0 scan
configures ath0 to join network “mynwid”, using WPA key
“mywpakey”, obtaining an IP address using DHCP:
nwid mynwid wpakey mywpakey
creates a host-based access point on boot:
nwid mynwid wpakey mywpakey
inet 192.168.1.1 255.255.255.0
- ath0: unable to attach hardware; HAL status N
- The Hardware Access Layer was unable to configure the hardware as
requested. The status code is explained in the HAL include file
- ath0: failed to allocate descriptors: N
- The driver was unable to allocate contiguous memory for the transmit and
receive descriptors. This usually indicates system memory is scarce and/or
- ath0: 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 happen.
- ath0: 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 not happen.
- ath0: 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
- ath0: 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.
- ath0: unable to reset hardware; hal status N
- 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 happen.
- ath0: unable to initialize the key cache
- The driver was unable to initialize the hardware key cache. This should
- ath0: unable to start recv logic
- The driver was unable to restart frame reception. This should not
- ath0: 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
- ath0: bogus xmit rate 0xNNNN
- An invalid transmit rate was specified for an outgoing frame. The frame is
discarded. This should not happen.
- ath0: ath_chan_set: unable to reset channel N (X MHz)
- The Hardware Access Layer was unable to reset the hardware when switching
channels during scanning. This should not happen.
- ath0: unable to allocate channel table
- The driver was unable to allocate memory for the table used to hold the
set of available channels.
- ath0: 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.
- ath0: failed to enable memory mapping
- The driver was unable to enable memory-mapped I/O to the PCI device
registers. This should not happen.
- ath0: 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.
- ath0: cannot map register space
- The driver was unable to map the device registers into the host address
space. This should not happen.
- ath0: could not map interrupt
- The driver was unable to allocate an IRQ for the device interrupt. This
should not happen.
- ath0: could not establish interrupt
- The driver was unable to install the device interrupt handler. This should
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.
ath driver was written by
Sam Leffler, and was ported to
OpenBSD by Reyk Floeter
who also wrote a free replacement of the binary-only HAL.
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.
Operation in the 2GHz band is restricted to 11b mode because the
driver does not support running the hardware in 11g mode.