Comment 103 for bug 765438

For me the issue is still present in Ubuntu 12.10.

I'm on emachines e725, shortly after the Quantal Quetzel was out, I tried to boot from the original 12.10 32bit iso (tried out both creating a live usb and burning cd), was able to get just the black screen. After modifying the relevant files to set additional boot parameters "acpi_backlight=vendor i915.invert_brightness=1", got normally working startup disk.

After installing Quantal I had to modify boot parameters also for the newly installed system's kernel.

With these parameters set, the system functions normally, except for one case, when I recently closed the laptop's lid while an external monitor was connected. After raising the lid, laptop's backlight again was completely off; I was able to get it working by entering the command "setpci -s 00:02.0 F4.B=0" in terminal (thanks to the other monitor). I couldn't reproduce the problem since then, though.