xf86 ddx: add vga arbiter support.

This adds support for using the libpciaccess interface for
vga arbitration support on top of a kernel which supports it.

Currently patches are queued for kernel 2.6.32 in jbarnes
pci tree, and shipping in Fedora kernel.

Co-authors:
Tiago Vignatti <tiago.vignatti@nokia.com>

Signed-off-by: Dave Airlie <airlied@redhat.com>

hw/xfree86/dri/dri.c

@@ -69,6 +69,7 @@ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include "mipointer.h"
 #include "xf86_OSproc.h"
 #include "inputstr.h"
+#include "xf86VGAarbiter.h"
 
 #define PCI_BUS_NO_DOMAIN(bus) ((bus) & 0xffu)
 
@@ -333,6 +334,12 @@ DRIScreenInit(ScreenPtr pScreen, DRIInfoPtr pDRIInfo, int *pDRMFD)
 	return FALSE;
     }
 
+    if (!xf86VGAarbiterAllowDRI(pScreen)) {
+        DRIDrvMsg(pScreen->myNum, X_WARNING,
+                  "Direct rendering is not supported when VGA arb is necessary for the device\n");
+	return FALSE;
+    }
+		
     /*
      * If Xinerama is on, don't allow DRI to initialise.  It won't be usable
      * anyway.