Comment 36 for bug 1392460

On a reboot the backlight is turned on very early in the process, before the driver is loaded, probably by the bios. This is obvious because grub is able to display, so on a reboot the driver does not have to turn on the backlight, it is already on, whereas on a resume the backlight needs to be explicitly turned on by the operating system since the bios is only involved to the extent of signalling the ACPI state. However even if there is a bug in the bios with respect to supporting whatever mechanism the driver is attempting to use to manage the hardware display state, on Ubuntu 13 and earlier the display was occasionally turned on by resume, whereas now it is never turned on.

Please tell me what I have to do to resolve the "incomplete" status of this problem.