I have a Sony E series laptop (64 bit) where keys Fn+F5 and Fn+F6 should control the screen brightness. On my machine these keys do control the brightness "slider", but they do not control the actual screen brightness. I am running Ubuntu 12.10. These keys did work to control screen brightness when running Ubuntu 12.04 LTS, but I updated to 12.10 to get EFI boot working correctly.

To date I have tried various kernel bootup options to get the keys working, but none have proved effective. I have tried;
acpi_osi=Linux acpi_backlight=vendor

I had an earlier Sony laptop and to get the brightness controls working on that I had to use a custom gsd_backlight_helper module in gnome-settings-daemon. I've tried that fix for my new Sony, but that also fails to get the brightness controls working.

I'm sure it must be possible to fix this issue, but I'm not sure how to proceed. Can anyone help with this?