Input / Output Advanced Programmable Interrupt Controller. More...

Collaboration diagram for IO APIC:

Detailed Description

Input / Output Advanced Programmable Interrupt Controller.

The IO APICs are used to route external interrupts to a CPUs local APIC. Each IO APIC handles a range of Global System Interrupts (GSIs) or in PatchworkOS terms, physical IRQs, which it receives from external devices such as a keyboard. The IO APIC then routes these physical IRQs to a local APIC using that local APICs ID, that local APIC then triggers the interrupt on its CPU.

So, for example, say we have two IO APICs, 0 and 1, where IO APIC 0 handles physical IRQs 0-23 and IO APIC 1 handles physical IRQs 24-47. Then lets say we want to route physical IRQ 1 to CPU 4. In this case, we would use IO APIC 0 to route physical IRQ 1 to the local APIC ID of CPU 4, lets say this ID is 5. The IO APIC would then send the interrupt to the local APIC with ID 5, which would then trigger the interrupt on CPU 4.

The range that each IO APIC handles is defined as the range [globalSystemInterruptBase, globalSystemInterruptBase + maxRedirs), where globalSystemInterruptBase is defined in the ACPI MADT table and maxRedirs is read from the IO APICs version register.

Note: The only reason there can be multiple IO APICs is for hardware implementation reasons, things we dont care about. As far as I know, the OS itself does not benefit from having multiple IO APICs.

See also: ACPI Specification Version 6.6; 82093AA I/O ADVANCED PROGRAMMABLE INTERRUPT CONTROLLER (IOAPIC)

Data Structures
struct	ioapic_version_t
	IO APIC Version Structure. More...

struct	ioapic_redirect_entry_t
	IO APIC Redirection Entry Structure. More...

Typedefs
typedef uint32_t	ioapic_gsi_t
	IO APIC Global System Interrupt type.

Enumerations
enum	ioapic_mmio_register_t { IOAPIC_MMIO_REG_SELECT = 0x00 , IOAPIC_MMIO_REG_DATA = 0x10 }
	IO APIC Memory Mapped Registers. More...

enum	ioapic_register_t { IOAPIC_REG_IDENTIFICATION = 0x00 , IOAPIC_REG_VERSION = 0x01 , IOAPIC_REG_ARBITRATION = 0x02 , IOAPIC_REG_REDIRECTION_BASE = 0x10 }
	IO APIC Registers. More...

enum	ioapic_delivery_mode_t { IOAPIC_DELIVERY_NORMAL = 0 , IOAPIC_DELIVERY_LOW_PRIO = 1 , IOAPIC_DELIVERY_SMI = 2 , IOAPIC_DELIVERY_NMI = 4 , IOAPIC_DELIVERY_INIT = 5 , IOAPIC_DELIVERY_EXTERNAL = 7 }
	IO APIC Delivery Modes. More...

enum	ioapic_destination_mode_t { IOAPIC_DESTINATION_PHYSICAL = 0 , IOAPIC_DESTINATION_LOGICAL = 1 }
	IO APIC Destination Modes. More...

enum	ioapic_trigger_mode_t { IOAPIC_TRIGGER_EDGE = 0 , IOAPIC_TRIGGER_LEVEL = 1 }
	IO APIC Trigger Modes. More...

enum	ioapic_polarity_t { IOAPIC_POLARITY_HIGH = 0 , IOAPIC_POLARITY_LOW = 1 }
	IO APIC Polarity Modes. More...

Functions
uint64_t	ioapic_all_init (void)
	Initialize all IO APICs found in the MADT.

Typedef Documentation

◆ ioapic_gsi_t

typedef uint32_t ioapic_gsi_t

IO APIC Global System Interrupt type.

Definition at line 38 of file ioapic.h.

Enumeration Type Documentation

◆ ioapic_mmio_register_t

enum ioapic_mmio_register_t

IO APIC Memory Mapped Registers.

Enumerator
IOAPIC_MMIO_REG_SELECT
IOAPIC_MMIO_REG_DATA

Definition at line 44 of file ioapic.h.

◆ ioapic_register_t

enum ioapic_register_t

IO APIC Registers.

Enumerator
IOAPIC_REG_IDENTIFICATION
IOAPIC_REG_VERSION
IOAPIC_REG_ARBITRATION
IOAPIC_REG_REDIRECTION_BASE

Definition at line 54 of file ioapic.h.

◆ ioapic_delivery_mode_t

enum ioapic_delivery_mode_t

IO APIC Delivery Modes.

Enumerator
IOAPIC_DELIVERY_NORMAL
IOAPIC_DELIVERY_LOW_PRIO
IOAPIC_DELIVERY_SMI
IOAPIC_DELIVERY_NMI
IOAPIC_DELIVERY_INIT
IOAPIC_DELIVERY_EXTERNAL

Definition at line 66 of file ioapic.h.

◆ ioapic_destination_mode_t

enum ioapic_destination_mode_t

IO APIC Destination Modes.

Enumerator
IOAPIC_DESTINATION_PHYSICAL
IOAPIC_DESTINATION_LOGICAL

Definition at line 80 of file ioapic.h.

◆ ioapic_trigger_mode_t

enum ioapic_trigger_mode_t

IO APIC Trigger Modes.

Enumerator
IOAPIC_TRIGGER_EDGE
IOAPIC_TRIGGER_LEVEL

Definition at line 90 of file ioapic.h.

◆ ioapic_polarity_t

enum ioapic_polarity_t

IO APIC Polarity Modes.

Enumerator
IOAPIC_POLARITY_HIGH
IOAPIC_POLARITY_LOW

Definition at line 100 of file ioapic.h.

Function Documentation

◆ ioapic_all_init()

uint64_t ioapic_all_init ( void )

Initialize all IO APICs found in the MADT.

Returns: On success, 0. On failure, ERR.

Definition at line 91 of file ioapic.c.

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