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+		Writing Device Drivers for Zorro Devices
+		----------------------------------------
+
+Written by Geert Uytterhoeven <geert@linux-m68k.org>
+Last revised: September 5, 2003
+
+
+1. Introduction
+---------------
+
+The Zorro bus is the bus used in the Amiga family of computers. Thanks to
+AutoConfig(tm), it's 100% Plug-and-Play.
+
+There are two types of Zorro busses, Zorro II and Zorro III:
+
+  - The Zorro II address space is 24-bit and lies within the first 16 MB of the
+    Amiga's address map.
+
+  - Zorro III is a 32-bit extension of Zorro II, which is backwards compatible
+    with Zorro II. The Zorro III address space lies outside the first 16 MB.
+
+
+2. Probing for Zorro Devices
+----------------------------
+
+Zorro devices are found by calling `zorro_find_device()', which returns a
+pointer to the `next' Zorro device with the specified Zorro ID. A probe loop
+for the board with Zorro ID `ZORRO_PROD_xxx' looks like:
+
+    struct zorro_dev *z = NULL;
+
+    while ((z = zorro_find_device(ZORRO_PROD_xxx, z))) {
+	if (!zorro_request_region(z->resource.start+MY_START, MY_SIZE,
+				  "My explanation"))
+	...
+    }
+
+`ZORRO_WILDCARD' acts as a wildcard and finds any Zorro device. If your driver
+supports different types of boards, you can use a construct like:
+
+    struct zorro_dev *z = NULL;
+
+    while ((z = zorro_find_device(ZORRO_WILDCARD, z))) {
+	if (z->id != ZORRO_PROD_xxx1 && z->id != ZORRO_PROD_xxx2 && ...)
+	    continue;
+	if (!zorro_request_region(z->resource.start+MY_START, MY_SIZE,
+				  "My explanation"))
+	...
+    }
+
+
+3. Zorro Resources
+------------------
+
+Before you can access a Zorro device's registers, you have to make sure it's
+not yet in use. This is done using the I/O memory space resource management
+functions:
+
+    request_mem_region()
+    release_mem_region()
+
+Shortcuts to claim the whole device's address space are provided as well:
+
+    zorro_request_device
+    zorro_release_device
+
+
+4. Accessing the Zorro Address Space
+------------------------------------
+
+The address regions in the Zorro device resources are Zorro bus address
+regions. Due to the identity bus-physical address mapping on the Zorro bus,
+they are CPU physical addresses as well.
+
+The treatment of these regions depends on the type of Zorro space:
+
+  - Zorro II address space is always mapped and does not have to be mapped
+    explicitly using z_ioremap().
+    
+    Conversion from bus/physical Zorro II addresses to kernel virtual addresses
+    and vice versa is done using:
+
+	virt_addr = ZTWO_VADDR(bus_addr);
+	bus_addr = ZTWO_PADDR(virt_addr);
+
+  - Zorro III address space must be mapped explicitly using z_ioremap() first
+    before it can be accessed:
+ 
+	virt_addr = z_ioremap(bus_addr, size);
+	...
+	z_iounmap(virt_addr);
+
+
+5. References
+-------------
+
+linux/include/linux/zorro.h
+linux/include/asm-{m68k,ppc}/zorro.h
+linux/include/linux/zorro_ids.h
+linux/drivers/zorro
+/proc/bus/zorro
+