Binary package hint: acpi-support
This is an IBM Thinkpad R40 2722-CDG running current edgy.
See also: https://wiki.ubuntu.com/LaptopTestingTeam/ThinkpadR40-2722
When I press Fn+F7 nothing happens. It should at least cycle through the available displays: lcd, crt, both, or even start a program to manage display profiles.
The first problem here is that the key does not even generate ACPI events because that is disabled in /etc/modprobe.d/ibm_acpi.modprobe. I assume that is because some Thinkpads do the right thing themselves when the key dosn't generate an event. Alas, mine doesn't and instead does nothing.
The second problem is that the ACPI event then has to trigger some action. The obvious candidate would be "echo video_switch > /proc/acpi/ibm/video" and friends, but unfortunately those don't work for me.
The best thing would be of course if all of this could be handled by X itself...
I thought the R40 worked fine using the hardware (BIOS) switching support. Which, as you note, is the reason that we leave it disabled. However some of the new Lenovopads need it doing in software, so perhaps we better look into whitelisting; or just using software switching across the board.
Can you include the output of:
cat /var/lib/
and confirm that all the other special keys /do/ work.