I'm using a Dell XPS 15, 13.04. In order to get my backlight brightness control to work I have to use "acpi_backlight=vendor dell_laptop.backlight=0". But when I boot, I get the message: dell_laptop: '0' invalid parameter for 'backlight', at which my computer then continues to boot and works normally, with the brightness control working. It seems that I can change the '0' to anything, get the same message with the '0' changed to whatever I changed it to, and the brightness control still works. How can I get the message to go away?