Several users have contacted me about an issue with BootChamp where after restarting into Windows 7 from BootChamp the brightness cannot be changed. When the user goes to change the brightness, nothing happens and the screen stays at the maximum brightness level.
This appears to be an OS bug, from what I’ve discovered.
BootChamp uses a built-in command in OS X called bless to set the startup disk. This tool has an option that only sets the startup disk for the next restart. The command is used in Terminal like so:
sudo bless --folder PATH --setBoot --legacy --nextonly
where PATH is the mounted volume path of a Windows volume, e.g. “/Volumes/Windows”.
When the —nextonly option is used, the OS will only boot into Windows for the next restart, and subsequent restarts will boot back into OS X. This works all fine and dandy, but apparently it causes the brightness controls to not work.
If you remove the —nextonly option, the brightness controls work fine, but you will keep restarting into Windows. Same goes for if you select the boot device through System Preferences, or by holding down Option immediately after the restart chime.
I’ve reported the bug to Apple, as there’s nothing else I can do from what I know about the issue currently.
There was a bug back around 10.6.3 where the —nextonly option didn’t work at all, but a later 10.6.x update fixed the issue, so hopefully Apple will address it in a future software update.