x11-drivers/xf86-video-fbdev-0.3.0 from xorg-x11-7.1 doesn't work with imacfb driver from linux-2.6.18-rc1. Native resolution from fbdev is 1440x990. The fbdev driver displays something but every thing is messed up. More information follows.
Created attachment 91486 [details] Log file from X server and fbdev driver
Created attachment 91491 [details] dmesg output of imacfb driver
Sounds like that driver isn't mature enough yet to handle X's fbdev. Please file a bug at https://bugs.freedesktop.org and post a link to it here. Thanks :)
More info: Xorg-7.0 worked fine with the driver. Xorg-7.1 only works correctly with the option "ShadowFB "0". Seems to be an error in the driver.
Alright, then please follow the instructions in comment #3 :)