I'm trying to compile myown 2.6.30-rc3 kernel to shave off stuff I don't need, make it preemptible and 1000hz (just for the heck of it), and enable intel kernel mode-setting by default. Upon compiling, however, I get the following error and the process stops.
acpi_video_register is defined in drivers/acpi/video.c, and somehow (?) it's not being included. There's also a "stub" of it in include/acpi/video.h, which only returns 0. Neither seems to be read?
drivers/built-in.o: In function `intel_opregion_init':
(.text+0xaefaa): undefined reference to `acpi_video_register'
make: *** [.tmp_vmlinux1] Error 1
make: Leaving directory `/usr/src/linux-2.6.29'
make: *** [debian/stamp/build/kernel] Error 2
Obviously I disabled something in the .config file I shouldn't have, but how do I tell what it is?