After shamelessly stealing the patches from http://svn.mandriva.com/cgi-bin/viewvc.cgi/packages/cooker/x11-driver-video-psb/current/SOURCES/, and some slight modifications to the ebuild, I was able to get everything working. Basic steps:
Apply the following patches (in addition to the ones already included in current ebuild):
- xserver-xorg-video-psb-0.31.0-assert.patch
- xserver-xorg-video-psb-0.31.0-comment_unused.patch
- xserver-xorg-video-psb-0.31.0-greedy.patch
- xserver-xorg-video-psb-0.31.0-loader.patch
- xserver-xorg-video-psb-0.31.0-xf86AddModuleInfo.patch
When building, you also need to set the CFLAGS to include -fvisibility=default.
Once this is done, just emerge like normal and your full Poulsbo graphics card will work with the latest stable Xorg 1.7. To make things easier, I have submitted a patch to Gentoo, you can download everything you need there into your own local overlay.