I've seen that this bug was already there, but i couldn't solve it with the instructions there. because the bug was related to cvs, i created a new one
When i compile mesa from git i got this:

<snip>
../common/vblank.c: In Funktion �driGetCurrentVBlank�:
../common/vblank.c:306: Fehler: �DRM_VBLANK_SECONDARY� nicht deklariert (erste Benutzung in dieser Funktion)
../common/vblank.c:306: Fehler: (Jeder nicht deklarierte Bezeichner wird nur einmal aufgef
../common/vblank.c:306: Fehler: f�r jede Funktion in der er auftritt.)
../common/vblank.c: In Funktion �driWaitForVBlank�:
../common/vblank.c:363: Fehler: �DRM_VBLANK_SECONDARY� nicht deklariert (erste Benutzung in dieser Funktion)
make[6]: *** [../common/vblank.o] Fehler 1
make[6]: Leaving directory `/usr/local/src/r300/mesa/src/mesa/drivers/dri/radeon'
make[5]: *** [subdirs] Fehler 1
make[5]: Leaving directory `/usr/local/src/r300/mesa/src/mesa/drivers/dri'
make[4]: *** [linux-solo] Fehler 2
make[4]: Leaving directory `/usr/local/src/r300/mesa/src/mesa'
make[3]: *** [default] Fehler 2
make[3]: Leaving directory `/usr/local/src/r300/mesa/src/mesa'
make[2]: *** [subdirs] Fehler 1
make[2]: Leaving directory `/usr/local/src/r300/mesa/src'
make[1]: *** [default] Fehler 1
make[1]: Leaving directory `/usr/local/src/r300/mesa'
make: *** [linux-dri-x86] Fehler 2
<snip>
i've compiled lib drm from git, too
my PKG_CONFIG_PATH is set to:
/usr/lib/pkgconfig:/lib/pkgconfig:/usr/qt/3/lib/pkgconfig
tryed also:
/usr/lib/pkgconfig seperatly

in /usr/lib/pkgconfig/libdrm.pc
content:
prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

Name: libdrm
Description: Userspace interface to kernel DRM services
Version: 2.3.0
Libs: -L${libdir} -ldrm
Cflags: -I${includedir} -I${includedir}/drm

linux-dri-x86:
# -*-makefile-*-
# Configuration for linux-dri: Linux DRI hardware drivers for XFree86 & others

include $(TOP)/configs/linux-dri

CONFIG_NAME = linux-dri-x86

# Unnecessary on x86, generally.
PIC_FLAGS = 
# Add -m32 to CFLAGS:
ARCH_FLAGS = -m32
DRI_DIRS = radeon r300
ASM_FLAGS = -DUSE_X86_ASM -DUSE_MMX_ASM -DUSE_3DNOW_ASM -DUSE_SSE_ASM
ASM_SOURCES = $(X86_SOURCES)
ASM_API = $(X86_API)

tryed also DRI_DIRS= radeon
and DRI_DIRS= r300

Note there is no other libdrm.pc in my path. i have deleted any other occurences
, i also deleted the old system  libdrm.* from /lib 

do you have any suggestions?
or do you need further information?

thanks for your help,

regards bjoern