--- wikisrc/users/rkujawa/g-rex.mdwn	2012/07/08 13:37:51	1.9
+++ wikisrc/users/rkujawa/g-rex.mdwn	2012/07/12 17:01:53	1.10
@@ -73,7 +73,7 @@ same vendor (8512) and product (101).
 
 0x80000000 - PCI memory space, variable size and number of boards, depending on cards installed. 
 
-# 2a. PCI configuration space (0xFFFA0000)
+# 2a. PCI configuration space (0xFFFC0000)
 
 Access to configuration space is a bit tricky. Be warned that access to 
 addresses not used by G-REX generates bus error (esp. to configuration 
@@ -81,12 +81,34 @@ locations which are unused because there
 how these errors are supported in your OS, it may be important to trap them and
 handle correctly. 
 
-Configuration data for first slot seems to be accessible at offset +0x1000 (on 
-CVPPC/BVPPC there's aslo a mirror on +0x0).
+Configuration data for first slot (device 0) is accessible at offset +0x1000, 
+location for the next slots can be obtained by shifting the bit:
 
-[TO BE COMPLETED]
+Configuration space address + (offset << device number)
+
+For example to obtain configuration space for the second slot (device 1): 
+
+0xFFFC0000 + (0x1000 << 1) = 0xFFFC2000
+
+For the third slot (device 2): 
+
+0xFFFC0000 + (0x1000 << 2) = 0xFFFC4000
+
+and so on.
+
+How to access device functions is not well analyzed, however funtion 0 is
+always available at address computed by the above equation. Function 1 is
+available at offset +0x100. One could assume that accessing the next
+device functions is possible by shifting the bit (as with device access),
+but that was not tested, becasue cards with more than two functions are not
+common. 
+
+On CVPPC/BVPPC configuration space is accessible at offset +0x0 (but there
+are also mirrors through whole configuration space).
+
+See [[p5pb_pci_conf_read()|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/p5pb.c#p5pb_pci_conf_read]] and [[p5pb_pci_conf_write()|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/p5pb.c#p5pb_pci_conf_read]] functions. 
 
-# 2b. PCI I/O registers space (0xFFFC0000)
+# 2b. PCI I/O registers space (0xFFFA0000)
 
 This space offers access to I/O registers of all PCI cards.
 
@@ -114,7 +136,8 @@ On CVPPC/BVPPC this space is present at 
 
 Offset - meaning
 
-0x0000 - Endianness swapper mode, write 0x02 to switch bridge into big endian mode
+0x0000 - Endianness swapper mode, write 0x02 to switch bridge into 
+big endian mode
 
 0x0010 - Interrupt enable, write 0x01 to enable interrupts (INT2 on Amiga side)
 
@@ -138,7 +161,8 @@ Differentiating between CVPPC/BVPPC and 
 by looking for Texas Instruments TVP4020 vendor and product ID at the beginning
 of PCI configuration space. Configuration data for Permedia 2 chip will be
 available at offset 0x0 on CVPPC/BVPPC, but on G-REX first slot is located
-at offset 0x1000. See [[p5pb_identify_bridge()|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/p5pb.c#p5pb_identify_bridge]] and [[p5pb_cvppc_probe()|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/p5pb.c#p5pb_cvppc_probe]] functions
+at offset 0x1000. See [[p5pb_identify_bridge()|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/p5pb.c#p5pb_identify_bridge]] 
+and [[p5pb_cvppc_probe()|http://nxr.netbsd.org/xref/src/sys/arch/amiga/pci/p5pb.c#p5pb_cvppc_probe]] functions
 in the NetBSD driver.
 
 # 4. Reconfiguring the bus
@@ -162,7 +186,8 @@ reverse engineering.
 [TO BE COMPLETED]
 
 
-G-REX 4000D probably has busmaster DMA capability in all slots.
+G-REX 4000D probably has busmaster DMA capability in all slots. G-REX 1200 has
+busmaster DMA in first or two first slots depending on hardware revision.
 
 # 7. Sample PCI bridge driver implementation