I can not use the backlight keys which is no real issues but when I log out 
the screen goes black with no cursor, using lxdm or not.  I have tried 
adding acpi_backlight=vendor, acpi_osi=Linux

acpi_osi="!Windows 2012", video.use_native_backlight=1, video.use_native_backlight=1, all with no change.  I suspect building kernel with backlight set is my only option unless someone here has any suggestions.