Bug#521712: This really is a bug.
linux-headers-2.6.29-1-686 is missing all the symlinks to
# ls -l /lib/modules/2.6.26-2-686/build/include/linux/agp_backend.h
lrwxrwxrwx 1 root root 66 Mar 30 19:30 /lib/modules/2.6.26-2-686/build/include/linux/agp_backend.h -> ../../../linux-headers-2.6.26-2-common/include/linux/agp_backend.h
# ls -l /lib/modules/2.6.29-1-686/build/include/linux/agp_backend.h
ls: cannot access /lib/modules/2.6.29-1-686/build/include/linux/agp_backend.h: No such file or directory
# ls -l /usr/src/linux-headers-2.6.29-1-common/include/linux/agp_backend.h
-rw-r--r-- 1 root root 3579 Mar 23 19:12 /usr/src/linux-headers-2.6.29-1-common/include/linux/agp_backend.h
This breaks anything that tries to access the kernel headers that the
/lib/modules/<version>/build is supposed to point to. The linux-headers
for 2.6.29 are severely broken it seems.
Just because someone posts a potential workaround (which really had
nothing to do with it) doesn't mean the original bug isn't in fact a bug.