ThinkPad 11a/b/g/n Wireless LAN Mini Express Adapter
To determine the chipset your card uses, issue the following commands:
# update-pciids # lspci | egrep -i 'network|atheros|wireless' 03:00.0 Network controller: Atheros Communications, Inc. AR5418 802.11a/b/g/n Wireless PCI Express Adapter (rev 01)
If you get something different than above despite having the most current PCI IDs, please report it here!
There is now active development of a free driver ath9k that aims to fully support the draft 11n protocol. It is available in the mainline linux kernel starting with 2.6.27 and therefore automatically included in any distribution running this kernel (eg. Ubuntu Intrepid Ibex). The version in this latest kernel however does not support "aggregation" which basically means you will only see a slight increase in speed from the 11g protocol (mesured as 25 Mb/s vs 20Mb/s). If your distribution does not yet include this kernel (aheghm Debian), you'll have to jump through a few hoops.
Madwifi is a native linux driver that used to use a binary-only HAL and so must be compiled separately from the kernel. The HAL has recently been opened up, however with the development of ath9k mentioned above, the future of this project in particular with regard to this chipset is uncertain. It does not support the draft 11n protocol, but will work in "legacy" 11g mode. Support for this chipset was initially planned for release 0.9.4, but this inclusion had to be postponed as a critical update with a bug fix for compilation with the 2.6.24 kernel was necessary before the pre-release trunk was sufficiently stable. Thus, it is still necessary to download the prerelease snapshot from trunk using subversion.
There is a howto, which describes the procedure for getting the snapshot to work.
There is an old ticket for this card at madwifi, #1001.
There is an new ticket for this card at madwifi-branch, #1243. Insert non-formatted text here
Using the Windows Driver in Linux
If you have a weak stomach for pre-release software, you can always use "ndiswrapper" (>= 1.29) to wrap the Windows driver supplied by Lenovo. This isn't as bad as you think. It does work like a charm, but you may have problems if you're using a 64 bit kernel since it's not clear that a 64 bit windows XP driver exists (ndiswrapper currently doesn't support Vista drivers). Here's the Howto.
Non-Maskable Interrupt with madwifi
A number of folks have reported getting errors while using the experimental madwifi driver with the AR5418. After hours of flawless operation, the Kernel sometimes throws an NMI after which, the wifi dies. Aside from rebooting, suspending (to ram or disk) and resuming seems to be the only method to recover.
Uhhuh. NMI received for unknown reason b0 on CPU 0. You have some hardware problem, likely on the PCI bus. Dazed and confused, but trying to continue
wifi0: rx FIFO overrun; resetting wifi0: rx FIFO overrun; resetting wifi0: rx FIFO overrun; resetting
A possible preventitive measure is issuing the command
# iwpriv <device> bgscan 0
each time you load the driver. To make this change "permanent", you could add this command to your distribution's ifup networking scripts as described below.
Open up /etc/network/interfaces in a text editor and find the entry for your wireless device. Which should look something like
iface wlan0 inet manual wpa-driver madwifi wpa-roam /etc/network/wpa_supplicant.conf
and add the line
post-up iwpriv wlan0 bgscan 0
to the end of it where of course you substitute your interface name (e.g., "ath0") for "wlan0".
In addition to hard-switching the wireless card, the switch also generates an acpi event on transition from hi->lo and vice versa. It is however the same event in both directions.