introducing support for other AGP devices?

I'm running FreeBSD 5.2.1-RELEASE on an E-machines M3505 laptop.
I've was hoping to get DRI working under X11.  Alas, I am thwarted.

The video card is an ATI Radeon Mobility U1.

  drm0_at_pci1:5:0:  class=0x030000 card=0x2029161f chip=0x43361002 rev=0x00 hdr=0x00
      vendor   = 'ATI Technologies'
      device   = 'Radeon Mobility U1'
      class    = display
      subclass = VGA

It was straightforward to patch sys/dev/drm/radeon.h to allow this
card to probe (gotta file a PR soonish):

   {0x1002, 0x4C57, 0, "ATI Radeon LW Mobility 7500 M7"},          \
 + {0x1002, 0x4336, 0, "ATI Radeon Mobility U1"}, \
   {0x1002, 0x4C58, 0, "ATI Radeon LX RV200 Mobility FireGL 7800 M7"}, \

  # dmesg | grep drm
  drm0: <ATI Radeon Mobility U1> port 0x9000-0x90ff mem 0xf0100000-0xf010ffff,0xf8000000-0xfbffffff irq 10 at device 5.0 on pci1
  info: [drm] Initialized radeon 1.10.0 20020828 on minor 0

But, X11R6 4.4.0 doesn't want to play, I get:

   "XFree86-DRI" missing on display ":0.0"

I've followed the advice on the DRI troubleshooting webpage:

  <http://dri.sourceforge.net/cgi-bin/moin.cgi/DriTroubleshooting>

I infer the core issue is this laptop's AGP chipset isn't supported,
acording to agp(4):

  pcib1_at_pci0:1:0: class=0x060400 card=0x00000000 chip=0x700f1002 rev=0x01 hdr=0x01
      vendor   = 'ATI Technologies'
      device   = 'A3/U1 PCI to AGP Bridge'
      class    = bridge
      subclass = PCI-PCI

It looks like FreeBSD-current has an easy-to-extend AGP structure
in sys/pci/.  But, other than introducing device probes, I have no
grasp how to pull in anything like support.

Any pointers?  I _think_ the Mobility U1 is also known as a 'IGP320M'
Northbridge chipset:

 <http://www20.tomshardware.com/mobile/20020516/radeon_igp320m-02.html>

(I'm grasping at straws here...)

Thanks for any advice.

-- 
Brian Reichert				<reichert_at_numachi.com>
37 Crystal Ave. #303			Daytime number: (603) 434-6842
Derry NH 03038-1713 USA			BSD admin/developer at large