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.

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https://bugs.launchpad.net/bugs/1392460

Title:
  resume hang ubuntu 14.10 kernel 3.16

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