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                Writing Device Drivers for Zorro Devices

                ----------------------------------------

Written by Geert Uytterhoeven 

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