linux/Documentation/sgi-ioc4.txt
<<
>>
Prefs
   1The SGI IOC4 PCI device is a bit of a strange beast, so some notes on
   2it are in order.
   3
   4First, even though the IOC4 performs multiple functions, such as an
   5IDE controller, a serial controller, a PS/2 keyboard/mouse controller,
   6and an external interrupt mechanism, it's not implemented as a
   7multifunction device.  The consequence of this from a software
   8standpoint is that all these functions share a single IRQ, and
   9they can't all register to own the same PCI device ID.  To make
  10matters a bit worse, some of the register blocks (and even registers
  11themselves) present in IOC4 are mixed-purpose between these several
  12functions, meaning that there's no clear "owning" device driver.
  13
  14The solution is to organize the IOC4 driver into several independent
  15drivers, "ioc4", "sgiioc4", and "ioc4_serial".  Note that there is no
  16PS/2 controller driver as this functionality has never been wired up
  17on a shipping IO card.
  18
  19ioc4
  20====
  21This is the core (or shim) driver for IOC4.  It is responsible for
  22initializing the basic functionality of the chip, and allocating
  23the PCI resources that are shared between the IOC4 functions.
  24
  25This driver also provides registration functions that the other
  26IOC4 drivers can call to make their presence known.  Each driver
  27needs to provide a probe and remove function, which are invoked
  28by the core driver at appropriate times.  The interface of these
  29IOC4 function probe and remove operations isn't precisely the same
  30as PCI device probe and remove operations, but is logically the
  31same operation.
  32
  33sgiioc4
  34=======
  35This is the IDE driver for IOC4.  Its name isn't very descriptive
  36simply for historical reasons (it used to be the only IOC4 driver
  37component).  There's not much to say about it other than it hooks
  38up to the ioc4 driver via the appropriate registration, probe, and
  39remove functions.
  40
  41ioc4_serial
  42===========
  43This is the serial driver for IOC4.  There's not much to say about it
  44other than it hooks up to the ioc4 driver via the appropriate registration,
  45probe, and remove functions.
  46
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.