Comment 5 for bug 668234

from https://bugs.launchpad.net/ubuntu/+source/linux/+bug/771758/comments/8 and https://bugs.launchpad.net/ubuntu/+source/linux/+bug/771758/comments/9:

I have tried pretty much all combinations of the brcm80211, wl, and acer_wmi modules on my Lenovo IdeaPad U160 and here's what I've found. The brcm80211 module/driver doesn't work under any conditions.

If I boot normally, with the acer_wmi and wl modules loaded automatically, then wifi doesn't work because of rfkill but I can't unblock them until I "sudo modprobe -r acer_wmi". Then wifi works fine. If I blacklist acer_wmi, wifi doesn't work again because of rfkill, but this time I can't unblock it until I "sudo modprobe acer_wmi" and then remove it again with "sudo modprobe -r acer_wmi".

So it seems like the acer_wmi module is doing some sort of necessary initialization without which the wl module and rfkill can't work. Hope that helps track down the real bug.

I fixed the problem on my U160 by abusing /etc/modprobe.d/broadcom-sta-common.conf. I replaced:

    install wl /sbin/modprobe --ignore-install wl $CMDLINE_OPTS

with:

    softdep wl pre: acer_wmi
    install wl /sbin/modprobe --ignore-install wl $CMDLINE_OPTS && rflist unblock all
    install acer_wmi /sbin/modprobe --ignore-install acer_wmi $CMDLINE_OPTS && /sbin/modprobe -r acer_wmi