В споре рождается истина

Hi all.
Finally, I’ve configured my Broadcom 4312 Wireless card in Arch Linux and can write something about this now.

First, you should determine the name of your card. Try to do

lspci | grep Broadcom

to see, what you have. You should see something like

04:00.0 Network controller: Broadcom Corporation BCM4312 802.11b/g LP-PHY (rev 01)

if you have Broadcom4312.

Also see what kernel do you have:

uname -r

All described below should work for 2.6.39-ARCH.

Also, I assume that you have internet already (or at least have access to the internet from other computer).
Go to this link http://www.broadcom.com/docs/linux_sta/README.txt and follow that instruction.
You should download source code of the driver, apply a patch and then compile it.
(should I write more detailed information here?)
After this, you will have file ‘wl.ko’.

Then unload from kernel some modules:

rmmod b43
rmmod ssb
rmmod wl

and load others:

modprobe lib80211
insmod wl.ko

then see, what is the name of the interface for you wireless card:

ifconfig -a

and up that interface:

ifconfig eth1 up

After this configure your connection.
Probably you should read about WPA_supplicant.
In my case, I’ve edited file /etc/wpa_supplicant.conf and run
wpa_supplicant -B -Dwext -i eth1 -c /etc/wpa_supplicant.conf

then you probably should do (if you have dhcp)

dhcpcd eth1

and you have internet, finally.