ACPI BIOS Error (bug): Could not resolve symbol [\_SB.PCI0.GP17.VGA.LCD._BCM.AFN7]
The ACPI driver attempted to evaluate (execute) the ACPI brightness control method for the screen but this failed because the ACPI AML byte code in your firmware did not have the object _SB.PCI0.GP17.VGA.LCD._BCM.AFN7 defined for some reason. The upshot of all of this is that the ACPI brightness control won't work. This is a firmware issue, I do not know of any workarounds apart from checking to see if you can get an updated BIOS firmware that may fix this.