sgi-ioc4.txt 2.0 KB

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