50 lines
2.1 KiB
Plaintext
50 lines
2.1 KiB
Plaintext
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====================================
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SGI IOC4 PCI (multi function) device
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====================================
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The SGI IOC4 PCI device is a bit of a strange beast, so some notes on
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it are in order.
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First, even though the IOC4 performs multiple functions, such as an
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IDE controller, a serial controller, a PS/2 keyboard/mouse controller,
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and an external interrupt mechanism, it's not implemented as a
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multifunction device. The consequence of this from a software
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standpoint is that all these functions share a single IRQ, and
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they can't all register to own the same PCI device ID. To make
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matters a bit worse, some of the register blocks (and even registers
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themselves) present in IOC4 are mixed-purpose between these several
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functions, meaning that there's no clear "owning" device driver.
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The solution is to organize the IOC4 driver into several independent
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drivers, "ioc4", "sgiioc4", and "ioc4_serial". Note that there is no
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PS/2 controller driver as this functionality has never been wired up
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on a shipping IO card.
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ioc4
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====
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This is the core (or shim) driver for IOC4. It is responsible for
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initializing the basic functionality of the chip, and allocating
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the PCI resources that are shared between the IOC4 functions.
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This driver also provides registration functions that the other
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IOC4 drivers can call to make their presence known. Each driver
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needs to provide a probe and remove function, which are invoked
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by the core driver at appropriate times. The interface of these
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IOC4 function probe and remove operations isn't precisely the same
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as PCI device probe and remove operations, but is logically the
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same operation.
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sgiioc4
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=======
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This is the IDE driver for IOC4. Its name isn't very descriptive
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simply for historical reasons (it used to be the only IOC4 driver
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component). There's not much to say about it other than it hooks
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up to the ioc4 driver via the appropriate registration, probe, and
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remove functions.
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ioc4_serial
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===========
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This is the serial driver for IOC4. There's not much to say about it
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other than it hooks up to the ioc4 driver via the appropriate registration,
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probe, and remove functions.
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