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Mauro Carvalho Chehab53708b82017-05-17 07:50:05 -03001====================================
2SGI IOC4 PCI (multi function) device
3====================================
4
Brent Casavant22329b52005-06-21 17:15:59 -07005The SGI IOC4 PCI device is a bit of a strange beast, so some notes on
6it are in order.
7
8First, even though the IOC4 performs multiple functions, such as an
9IDE controller, a serial controller, a PS/2 keyboard/mouse controller,
10and an external interrupt mechanism, it's not implemented as a
11multifunction device. The consequence of this from a software
12standpoint is that all these functions share a single IRQ, and
13they can't all register to own the same PCI device ID. To make
14matters a bit worse, some of the register blocks (and even registers
15themselves) present in IOC4 are mixed-purpose between these several
16functions, meaning that there's no clear "owning" device driver.
17
18The solution is to organize the IOC4 driver into several independent
19drivers, "ioc4", "sgiioc4", and "ioc4_serial". Note that there is no
20PS/2 controller driver as this functionality has never been wired up
21on a shipping IO card.
22
23ioc4
24====
25This is the core (or shim) driver for IOC4. It is responsible for
26initializing the basic functionality of the chip, and allocating
27the PCI resources that are shared between the IOC4 functions.
28
29This driver also provides registration functions that the other
30IOC4 drivers can call to make their presence known. Each driver
31needs to provide a probe and remove function, which are invoked
32by the core driver at appropriate times. The interface of these
33IOC4 function probe and remove operations isn't precisely the same
34as PCI device probe and remove operations, but is logically the
35same operation.
36
37sgiioc4
38=======
39This is the IDE driver for IOC4. Its name isn't very descriptive
40simply for historical reasons (it used to be the only IOC4 driver
41component). There's not much to say about it other than it hooks
42up to the ioc4 driver via the appropriate registration, probe, and
43remove functions.
44
45ioc4_serial
46===========
47This is the serial driver for IOC4. There's not much to say about it
48other than it hooks up to the ioc4 driver via the appropriate registration,
49probe, and remove functions.