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0001 The SGI IOC4 PCI device is a bit of a strange beast, so some notes on
0002 it are in order.
0003 
0004 First, even though the IOC4 performs multiple functions, such as an
0005 IDE controller, a serial controller, a PS/2 keyboard/mouse controller,
0006 and an external interrupt mechanism, it's not implemented as a
0007 multifunction device.  The consequence of this from a software
0008 standpoint is that all these functions share a single IRQ, and
0009 they can't all register to own the same PCI device ID.  To make
0010 matters a bit worse, some of the register blocks (and even registers
0011 themselves) present in IOC4 are mixed-purpose between these several
0012 functions, meaning that there's no clear "owning" device driver.
0013 
0014 The solution is to organize the IOC4 driver into several independent
0015 drivers, "ioc4", "sgiioc4", and "ioc4_serial".  Note that there is no
0016 PS/2 controller driver as this functionality has never been wired up
0017 on a shipping IO card.
0018 
0019 ioc4
0020 ====
0021 This is the core (or shim) driver for IOC4.  It is responsible for
0022 initializing the basic functionality of the chip, and allocating
0023 the PCI resources that are shared between the IOC4 functions.
0024 
0025 This driver also provides registration functions that the other
0026 IOC4 drivers can call to make their presence known.  Each driver
0027 needs to provide a probe and remove function, which are invoked
0028 by the core driver at appropriate times.  The interface of these
0029 IOC4 function probe and remove operations isn't precisely the same
0030 as PCI device probe and remove operations, but is logically the
0031 same operation.
0032 
0033 sgiioc4
0034 =======
0035 This is the IDE driver for IOC4.  Its name isn't very descriptive
0036 simply for historical reasons (it used to be the only IOC4 driver
0037 component).  There's not much to say about it other than it hooks
0038 up to the ioc4 driver via the appropriate registration, probe, and
0039 remove functions.
0040 
0041 ioc4_serial
0042 ===========
0043 This is the serial driver for IOC4.  There's not much to say about it
0044 other than it hooks up to the ioc4 driver via the appropriate registration,
0045 probe, and remove functions.