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========================================
Writing Device Drivers for Zorro Devices
========================================
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:Author: Written by Geert Uytterhoeven <geert@linux-m68k.org>
:Last revised: September 5, 2003
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Introduction
------------
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The Zorro bus is the bus used in the Amiga family of computers. Thanks to
AutoConfig(tm), it's 100% Plug-and-Play.

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There are two types of Zorro buses, Zorro II and Zorro III:
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  - 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.


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Probing for Zorro Devices
-------------------------
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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::
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    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"))
	...
    }

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``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::
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    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"))
	...
    }


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Zorro Resources
---------------
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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
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functions::
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    request_mem_region()
    release_mem_region()

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Shortcuts to claim the whole device's address space are provided as well::
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    zorro_request_device
    zorro_release_device


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Accessing the Zorro Address Space
---------------------------------
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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
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    and vice versa is done using::
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	virt_addr = ZTWO_VADDR(bus_addr);
	bus_addr = ZTWO_PADDR(virt_addr);

  - Zorro III address space must be mapped explicitly using z_ioremap() first
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    before it can be accessed::
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	virt_addr = z_ioremap(bus_addr, size);
	...
	z_iounmap(virt_addr);


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References
----------
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#. linux/include/linux/zorro.h
#. linux/include/uapi/linux/zorro.h
#. linux/include/uapi/linux/zorro_ids.h
#. linux/arch/m68k/include/asm/zorro.h
#. linux/drivers/zorro
#. /proc/bus/zorro
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