remove libdss from Makefile
[GitHub/moto-9609/android_kernel_motorola_exynos9610.git] / Documentation / sgi-ioc4.txt
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.