Bug 4099

My machine has several PCI video cards.  linux lspci says:

00:10.0 VGA compatible controller: Matrox Graphics, Inc. MGA 2164W [Millennium II]
00:12.0 VGA compatible controller: Matrox Graphics, Inc. MGA 2164W [Millennium II]
00:14.0 VGA compatible controller: Matrox Graphics, Inc. MGA 2164W [Millennium II]

The last one is the bios primary card.

Former versions of xorg/xfree86 were able to talk to all of them in one xinerama
session.  Trying to recreate  6.8.2. xorg.conf configuration from scratch is
failing to find the second and third cards.  Xorg.log says this in excerpts:

(II) PCI: 00:10:0: chip 102b,051b card 102b,0300 rev 00 class 03,00,00 hdr 00
(II) PCI: 00:12:0: chip 102b,051b card 102b,0300 rev 00 class 03,00,00 hdr 00
(II) PCI: 00:14:0: chip 102b,051b card 102b,0300 rev 00 class 03,00,00 hdr 00

(--) PCI: (0:16:0) Matrox Graphics, Inc. MGA 2164W [Millennium II] rev 0, Mem @
0xf8000000/24, 0xfebf0000/14, 0xfd000000/23, BIOS @ 0xfebb0000/16
(--) PCI: (0:18:0) Matrox Graphics, Inc. MGA 2164W [Millennium II] rev 0, Mem @
0xf9000000/24, 0xfebf4000/14, 0xfd800000/23, BIOS @ 0xfebc0000/16
(--) PCI:*(0:20:0) Matrox Graphics, Inc. MGA 2164W [Millennium II] rev 0, Mem @
0xfa000000/24, 0xfebfc000/14, 0xfe000000/23, BIOS @ 0xfebe0000/16

(II) Primary Device is: PCI 00:14:0
(WW) MGA: No matching Device section for instance (BusID PCI:0:16:0) found
(WW) MGA: No matching Device section for instance (BusID PCI:0:18:0) found

Note how the card number is sometimes printed in hex and sometimes in decimal.

In the xorg.conf file, I found no workable way of referring to the second and
third video cards by any PCI BUSID, to enable a multiheaded display.  (Variants
included PCI:0:16:0, PCI:0:10:0, PCI:0:0x10:0).