On my Samsung R24plusF000 laptop ATI Mobility Radeon X2300 has non-ATI PCI vendor ID. As a result X does not start with radeonhd driver. I see "No device found" in Xorg.log.

Video card presented in the system as:
Vendor ID: 0x0001
Device ID: 0x7188
Subsystem vendor ID: 0x144D
Subsystem device ID: 0xC515

Patch below resolves this problem for me, but it is ugly for PCI_VENDOR_ID_ATI replacement.

After recompiling with this patch applyed my display starts in 1280x800 resolution which is native for my panel.

diff -Naur old/src/rhd_driver.c new/src/rhd_driver.c
--- old/src/rhd_driver.c	2007-11-24 23:32:43.000000000 +0200
+++ new/src/rhd_driver.c	2007-11-29 22:02:14.000000000 +0200
@@ -361,7 +361,7 @@
 
     /* PCI BUS */
     if (xf86GetPciVideoInfo() ) {
-	numUsed = xf86MatchPciInstances(RHD_NAME, PCI_VENDOR_ATI,
+	numUsed = xf86MatchPciInstances(RHD_NAME, 0x0001,
 					RHDChipsets, RHDPCIchipsets,
 					devSections,numDevSections,
 					drv, &usedChips);
diff -Naur old/src/rhd_id.c new/src/rhd_id.c
--- old/src/rhd_id.c	2007-11-24 23:32:43.000000000 +0200
+++ new/src/rhd_id.c	2007-11-29 22:01:03.000000000 +0200
@@ -460,6 +460,7 @@
     /* 0x7186 : M64 : Mobility Radeon X1450 */
     /* 0x7187 : RV516 : Radeon X1300/X1550 */
     /* 0x7188 : M64 : Mobility Radeon X2300 */
+    { 0x7188, 0xC515, 0x144D, "Samsung R25plusF000 ATI Radeon X2300", RHD_CARD_FLAG_NONE, ID_CONNECTORINFO_EMPTY },
     /* 0x718A : M64 : Mobility Radeon X2300 */
     /* 0x718B : M62 : Mobility Radeon X1350 */
     /* 0x718C : M62 : Mobility Radeon X1350 */