From looking around:
Originally Posted by cnkk
This is needed to set the backlight driver to the vendor's one, as the default doesn't work correctly. Nomodeset turns off KMS for the driver to work, because it doesn't seem to do anything otherwise :S In practice you lose a bit of the WOW during boot.
If set to vendor, prefer vendor specific driver
(e.g. thinkpad_acpi, sony_acpi, etc.) instead
of the ACPI video.ko driver.
I understand the eject button opens the tray, but it also wrongly tells Ubuntu that the cdrom drive has been unplugged (or so I think), because mounting never works after that. Instead, if you just use the command 'eject cdrom', it will mount the CD automatically when you close the tray
Sorry if I can't be more specific, I just found those commands here in the forums too