Comment 121 for bug 277589

Have just installed Ubuntu Lucid Lynx (10.04) and unsurprisingly FN brightness keys didn't work. Just to remind that I have Sony FE31HR with Nvidia 7400 on board. Solution #112 leads exactly to benste's problems (#113). Also I tried the following solution (it is one solution in forum posts):

http://ubuntuforums.org/showthread.php?t=1420341#6
http://www.nvnews.net/vbulletin/showthread.php?t=143025&page=4

But it doesn't work as well.

So I ended with ACPI mix up solution that is OK for me:
1) put the sony.fdi file into /etc/hal/fdi/preprobe/ folder to disable HAL handlers
2) run acpi_listen and press FN+brightness-down, FN+brighntess-up and see the output. In my case the keys were FN+F5 and FN+F6 and here is my output:

sony/hotkey SNC 00000001 00000010
sony/hotkey SNC 00000001 0000003b
sony/hotkey SNC 00000001 00000011
sony/hotkey SNC 00000001 0000003b

Thus my FN+brightness-up="SNC 00000001 00000010 " and FN+brightness-down="SNC 00000001 00000011"
3) Adjust the files sony-brightness-up and sony-brightness-down with your key codes respectively and place the files to /etc/acpi/events
4) Copy sony-brn-up and sony-brn-down to /etc/acpi
5) Reboot

Now FN keys must be working. Notifications are not displayed but it is better than nothing :)
Of course it is not a solution for the bug, but a some workaround anyway.