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Based on kernel version 4.13.3. Page generated on 2017-09-23 13:56 EST.

1	====================================
2	SGI IOC4 PCI (multi function) device
3	====================================
4	
5	The SGI IOC4 PCI device is a bit of a strange beast, so some notes on
6	it are in order.
7	
8	First, even though the IOC4 performs multiple functions, such as an
9	IDE controller, a serial controller, a PS/2 keyboard/mouse controller,
10	and an external interrupt mechanism, it's not implemented as a
11	multifunction device.  The consequence of this from a software
12	standpoint is that all these functions share a single IRQ, and
13	they can't all register to own the same PCI device ID.  To make
14	matters a bit worse, some of the register blocks (and even registers
15	themselves) present in IOC4 are mixed-purpose between these several
16	functions, meaning that there's no clear "owning" device driver.
17	
18	The solution is to organize the IOC4 driver into several independent
19	drivers, "ioc4", "sgiioc4", and "ioc4_serial".  Note that there is no
20	PS/2 controller driver as this functionality has never been wired up
21	on a shipping IO card.
22	
23	ioc4
24	====
25	This is the core (or shim) driver for IOC4.  It is responsible for
26	initializing the basic functionality of the chip, and allocating
27	the PCI resources that are shared between the IOC4 functions.
28	
29	This driver also provides registration functions that the other
30	IOC4 drivers can call to make their presence known.  Each driver
31	needs to provide a probe and remove function, which are invoked
32	by the core driver at appropriate times.  The interface of these
33	IOC4 function probe and remove operations isn't precisely the same
34	as PCI device probe and remove operations, but is logically the
35	same operation.
36	
37	sgiioc4
38	=======
39	This is the IDE driver for IOC4.  Its name isn't very descriptive
40	simply for historical reasons (it used to be the only IOC4 driver
41	component).  There's not much to say about it other than it hooks
42	up to the ioc4 driver via the appropriate registration, probe, and
43	remove functions.
44	
45	ioc4_serial
46	===========
47	This is the serial driver for IOC4.  There's not much to say about it
48	other than it hooks up to the ioc4 driver via the appropriate registration,
49	probe, and remove functions.
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