1==================================== 2SGI IOC4 PCI (multi function) device 3==================================== 4 5The 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. 50