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.Dd June 23, 2003
.Dt ATH 4
.Os
.Sh NAME
.Nm ath
.Nd "Atheros IEEE 802.11 driver"
.Sh SYNOPSIS
.Cd "device ath"
.Sh DESCRIPTION
The
.Nm
driver provides support for wireless network adapters based on
the Atheros AR5210, AR5211, and AR5212 chips.
Chip-specific support is provided by the Atheros Hardware Access Layer
(HAL), that is packaged separately.
.Pp
Supported features include 802.11 and 802.3 frames, power management, BSS,
IBSS, and host-based access point operation modes.
All host/device interaction is via DMA.
.Pp
The
.Nm
driver encapsulates all IP and ARP traffic as 802.11 frames, however
it can receive either 802.11 or 802.3 frames.
Transmit speed and operating mode is selectable
depending on your hardware.
AR5210-based devices support 802.11a operation with trasmit speeds
of 6 Mbps, 9 Mbps, 12 Mbps, 18 Mbps, 24 Mbps, 36 Mbps, 48 Mbps, and 54 Mbps.
AR5211-based devices support 802.11a and 802.11b operation with transmit
speeds as above for 802.11a operation and
1Mbps, 2Mbps, 5.5 Mbps and 11Mbps for 802.11b operation.
AR5212-based devices support 802.11a, 802.11b, and 802.11g operation
with transmit speeds appropriate to each.
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.
All chips support WEP encryption.
AR5211 and AR5212 support the AES, TKIP, and Michael cryptographic
operations required for WPA but at this time the driver does support them.
To enable encryption, use
.Xr ifconfig 8
as shown below.
.Pp
By default, the
.Nm
driver configures the card for BSS operation (aka infrastructure
mode).
This mode requires the use of an access point (base station).
.Pp
The
.Nm
driver also supports the standard IBSS point-to-point mode
where stations can communicate amongst themselves without the
aid of an access point.
.Pp
The driver may also be configured to operate in hostap mode.
In this mode a host may function as an access point (base station).
Access points are different than operating in IBSS mode.
They operate in BSS mode.
They allow for easier roaming and bridge all ethernet traffic such
that machines connected via an access point appear to be on the local
ethernet segment.
.Pp
For more information on configuring this device, see
.Xr ifconfig 8 .
.Pp
Devices supported by the
.Nm
driver come in either Cardbus or mini-PCI packages.
Wireless cards in Cardbus slots may be inserted and ejected on the fly.
.Pp
The following cards are among those supported by the
.Nm
driver:
.Pp
.Bl -column -compact "D-Link DWL-AG650" "AR5212" "Cardbus"
.Em "Card	Chip	Bus"
D-Link DWL-AB650	AR5211	Cardbus
D-Link DWL-AG520	AR5212	Cardbus
D-Link DWL-AG650	AR5212	PCI
Linksys WMP55AG	AR5212	Cardbus
Linksys WPC51AB	AR5211	Cardbus
Linksys WPC55AG	AR5212	PCI
Netgear WAB501	AR5211	Cardbus
Netgear WAG511	AR5212	Cardbus
.El
.Sh EXAMPLES
Join an existing BSS network (ie: connect to an access point):
.Pp
.Dl "ifconfig ath0 inet 192.168.0.20 netmask 0xffffff00"
.Pp
Join a specific BSS network with network name
.Dq Li my_net :
.Pp
.Dl "ifconfig ath0 inet 192.168.0.20 netmask 0xffffff00 ssid my_net"
.Pp
Join a specific BSS network with WEP encryption:
.Bd -literal -offset indent
ifconfig ath0 inet 192.168.0.20 netmask 0xffffff00 ssid my_net \e
	wepmode on wepkey 0x8736639624
.Ed
.Pp
Join/create an 802.11b IBSS network with network name
.Dq Li my_net :
.Bd -literal -offset indent
ifconfig ath0 inet 192.168.0.22 netmask 0xffffff00 ssid my_net \e
	mode 11b mediaopt adhoc
.Ed
.Pp
Create an 802.11g host-based access point:
.Bd -literal -offset indent
ifconfig ath0 inet 192.168.0.10 netmask 0xffffff00 ssid my_ap \e
	mode 11g mediaopt hostap
.Ed
.Pp
Create an 802.11a host-based access point with WEP enabled:
.Bd -literal -offset indent
ifconfig ath0 inet 192.168.0.10 netmask 0xffffff00 ssid my_ap \e
	wepmode on wepkey 0x1234567890 mode 11a mediaopt hostap
.Ed
.Pp
Create a host-based wireless bridge to fxp0:
.Bd -literal -offset indent
Add BRIDGE to the kernel config.
ifconfig ath0 inet up ssid my_ap media DS/11Mbps mediaopt hostap
sysctl net.link.ether.bridge=1
sysctl net.link.ether.bridge_cfg="ath0 fxp0"
sysctl net.inet.ip.forwarding=1
.Ed
.Pp
This will give you the same functionality as an access point.
.Sh DIAGNOSTICS
.Bl -diag
.It "ath%d: unable to attach hardware; HAL status %u"
The Atheros Hardware Access Layer was unable to configure the hardware
as requested.
The status code is explained in the HAL include file
.Pa sys/contrib/dev/ath/ah.h .
.It "ath%d: failed to allocate descriptors: %d"
The driver was unable to allocate contiguous memory for the transmit
ad receive descriptors.
This usually indicates system memory is scarce and/or fragmented.
.It "ath%d: unable to setup a data xmit queue!"
The request to the HAL to setup the transmit queue for normal
data frames failed.
This should not happen.
.It "ath%d: unable to setup a beacon xmit queue!"
The request to the HAL to setup the transmit queue for 802.11 beacon frames
frames failed.
This should not happen.
.It "ath%d: 802.11 address: %s"
The MAC address programmed in the EEPROM is displayed.
.It "ath%d: hardware error; resetting"
A nunrecoverable error in the hardware occurred.
Errors of this sort include unrecoverable DMA errors.
The driver will reset the hardware and continue.
.It "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.
.It "ath%d: unable to reset hardware; hal status %u"
The Atheros Hardware Access Layer was unable to reset the hardware
as requested.
The status code is explained in the HAL include file
.Pa sys/contrib/dev/ath/ah.h .
This should not happen.
.It "ath%d: unable to start recv logic"
The driver was unable to restart frame reception.
This should not happen.
.It "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 hapen.
.It "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.
.It "ath%d: ath_chan_set: unable to reset channel %u (%u Mhz)"
The Atheros Hardware Access Layer was unable to reset the hardware
when switching channels during scanning.
This should not happen.
.It "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.
.It "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.
.It "ath%d: %s: %dM -> %dM (%d ok, %d err, %d retr)"
The driver's rate control algorithm changed the current rate for transmitting
frames.
This message is temporarily enabled for normal use to help in diagnosing
and improving the rate control algorithm.
The message indicates the new and old transmit rates and the statistics
it used to decide on this change.
.It "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.
.It "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.
.It "ath%d: cannot map register space"
The driver was unable to map the device registers into the host address space.
This should not happen.
.It "ath%d: could not map interrupt"
The driver was unable to allocate an IRQ for the device interrupt.
This should not happen.
.It "ath%d: could not establish interrupt"
The driver was unable to install the device interrupt handler.
This should not happen.
.El
.Sh SEE ALSO
.Xr an 4 ,
.Xr arp 4 ,
.Xr ath_hal 4,
.Xr card 4 ,
.Xr netintro 4 ,
.Xr pcic 4 ,
.Xr wi 4 ,
.Xr wlan 4 ,
.Xr ifconfig 8 ,
.Xr wicontrol 8
.Re
.Sh HISTORY
The
.Nm
device driver first appeared in
.Fx 5.2 .
.Sh CAVEATS
Different regulatory domains have different default channels for adhoc
mode.
See
.Xr ifconfig 8
for information on how to change the channel.
See
.Xr wicontrol 8
for information on different regulatory domains.
.Pp
802.11g support is little tested and may have interoperabity problems.
The software is known to function with an Atheros 11g access point but
interoperability may be problematic until vendors update firmware in
existing 11g products.
If you encounter problems using an 11g access point you should be able
to workaround incompatibilities by locking the driver to 11b mode.
Alternatively, most 11g compatibility issues are in the 802.11 layer
and you may be able to workaround issues by modifying the
.Xr wlan 4
module.
.Pp
Atheros Turbo mode is untested.
.Sh BUGS
.Pp
Roaming mode is broken.
If you lose your access point by going out of
range the driver does not automaticaly re-associate.
.Pp
Adhoc mode is untested and possibly/probably broken.
.Pp
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 one (hint: all the information needed is availble to the driver).
.Pp
General performance is suboptimal.
The Atheros hardware is known to be capable of transfer rates of 23-34 Mb/s
(or more) in 11a and 11g modes using their NDIS (aka Windows) driver.
Results with this driver are mixed and seem to vary significantly.
.Pp
It has been observed that getting a DHCP address sometimes requires
multiple tries.
This seems to happen only with AR5211 and AR5212 parts and mostly
in a noisy environment (i.e. one where many access points are found).
This problem is specific to the driver and not the hardware.
.Pp
The driver does not fully enable power-save operation of the chip;
consequently power use is suboptimal.