IOAPIC Namespace Reference

Abstraction of the I/O APIC that is used for management of external interrupts. More...

Classes
union	Identification
	I/O APIC Identification. More...
union	RedirectionTableEntry
	Entry in the redirection table. More...

Structs
struct	Identification.__unnamed__

Typedefs
typedef uint32_t	Index
typedef uint32_t	Register

Enumerations
enum	DeliveryMode {   FIXED = 0,   LOWEST_PRIORITY = 1,   SMI = 2,   NMI = 4,   INIT = 5,   EXTERN_INT = 7 }
	Delivery mode specifies the type of interrupt sent to the CPU. More...
enum	DestinationMode {   PHYSICAL = 0,   LOGICAL = 1 }
	Way of interpreting the value written to the destination field. More...
enum	Polarity {   HIGH = 0,   LOW = 1 }
	Interrupt polarity for the redirection-table entry. More...
enum	TriggerMode {   EDGE = 0,   LEVEL = 1 }
	Trigger mode. More...
enum	DeliveryStatus {   IDLE = 0,   SEND_PENDING = 1 }
	Interrupt state. More...
enum	InterruptMask {   UNMASKED = 0,   MASKED = 1 }
	Interrupt masking. More...

Functions
void	init ()
	Initializes the I/O APIC. More...
void	config (uint8_t slot, Core::Interrupt::Vector vector, TriggerMode trigger_mode=TriggerMode::EDGE, Polarity polarity=Polarity::HIGH)
	Creates a mapping between an interrupt vector and an external interrupt. More...
void	allow (uint8_t slot)
	Enables the redirection of particular external interrupts to the CPU(s). More...
void	forbid (uint8_t slot)
	Selectively masks external interrupts by slot number. More...
bool	status (uint8_t slot)
	Check whether an external interrupt source is masked. More...

Constants
volatile Index *	IOREGSEL_REG = reinterpret_cast<volatile Index*>(0xfec00000)
	IOAPIC registers memory mapped into the CPU's address space. More...
volatile Register *	IOWIN_REG = reinterpret_cast<volatile Register*>(0xfec00010)
	IOAPIC registers memory mapped into the CPU's address space. More...
const Index	IOAPICID_IDX = 0x00
const Index	IOREDTBL_IDX = 0x10
const uint8_t	slot_max = 24

Detailed Description

Abstraction of the I/O APIC that is used for management of external interrupts.

The I/O APIC's Core component is the IO-redirection table. This table is used to configure a flexible mapping between the interrupt number and the external interruption. Entries within this table have a width of 64 bit. For convenience, the union IOAPIC::RedirectionTableEntry should be used for modifying these tables (see file ioapic_registers.h for details).

Enumeration Type Documentation

DeliveryMode

enum IOAPIC::DeliveryMode

Delivery mode specifies the type of interrupt sent to the CPU.

Enumerator
FIXED	"ordinary" interrupt; send to ALL cores listed in the destination bit mask
LOWEST_PRIORITY	"ordinary" interrupt; send to the lowest priority core from destination mask
SMI	System Management Interrupt; vector number required to be 0.
NMI	Non-Maskable Interrupt, vector number ignored, only edge triggered.
INIT	Initialization interrupt (always treated as edge triggered)
EXTERN_INT	external interrupt (only edge triggered)

DestinationMode

enum IOAPIC::DestinationMode

Way of interpreting the value written to the destination field.

Enumerator
PHYSICAL	Destination contains the physical destination APIC ID.
LOGICAL	Destination contains a mask of logical APIC IDs.

Polarity

enum IOAPIC::Polarity

Interrupt polarity for the redirection-table entry.

Enumerator
HIGH	active high
LOW	active low

TriggerMode

enum IOAPIC::TriggerMode

Trigger mode.

Enumerator
EDGE	edge triggered
LEVEL	level triggered

DeliveryStatus

enum IOAPIC::DeliveryStatus

Interrupt state.

Enumerator
IDLE	No activity for this interrupt.
SEND_PENDING	Interrupt will be sent as soon as the bus / LAPIC is ready.

InterruptMask

enum IOAPIC::InterruptMask

Interrupt masking.

Enumerator
UNMASKED	Redirection-table entry is active (non-masked)
MASKED	Redirection-table entry is inactive (masked)

Function Documentation

init()

void IOAPIC::init

(

)

Initializes the I/O APIC.

This function will initialize the I/O APIC by initializing the IO-redirection table with sane default values. The default interrupt-vector number is chosen such that, in case the interrupt is issued, the panic handler is executed. In the beginning, all external interrupts are disabled within the I/O APIC. Apart from the redirection table, the APICID (read from the system description tables during boot) needs to be written to the IOAPICID register (see APIC::getIOAPICID() )

config()

void IOAPIC::config	(	uint8_t	slot,
		Core::Interrupt::Vector	vector,
		TriggerMode	trigger_mode = TriggerMode::EDGE,
		Polarity	polarity = Polarity::HIGH
	)

Creates a mapping between an interrupt vector and an external interrupt.

Parameters

slot	Number of the slot (i.e., the external interrupt) to configure.
vector	Number of the interrupt vector that will be issued for the external interrupt.
trigger_mode	Edge or level triggered interrupt signaling (level-triggered interrupts required for the optional serial interface)
polarity	Polarity of the interrupt signaling (active high or active low)

allow()

void IOAPIC::allow

(

uint8_t

slot

)

Enables the redirection of particular external interrupts to the CPU(s).

To fully enable interrupt handling, the interrupts must be enabled for every CPU (e.g., by calling Core::Interrupt::enable() in main)

Parameters

slot	Number of the external interrupt that should be enabled.

forbid()

void IOAPIC::forbid

(

uint8_t

slot

)

Selectively masks external interrupts by slot number.

Parameters

slot	Slot number of the interrupt to be disabled.

status()

bool IOAPIC::status

(

uint8_t

slot

)

Check whether an external interrupt source is masked.

Parameters

slot	Slot number of the interrupt to be checked.

Returns

Returns true iff the interrupt is unmasked, false otherwise

Constant Documentation

IOREGSEL_REG

volatile Index * IOAPIC::IOREGSEL_REG = reinterpret_cast<volatile Index*>(0xfec00000)

IOAPIC registers memory mapped into the CPU's address space.

Access to the actual IOAPIC registers can be obtained by performing the following steps:

1. Write the number of the IOAPIC register to the address stored in IOREGSEL_REG
2. Read the value from / write the value to the address referred to by IOWIN_REG.

See also

IO-APIC manual

IOWIN_REG

volatile Register * IOAPIC::IOWIN_REG = reinterpret_cast<volatile Register*>(0xfec00010)

IOAPIC registers memory mapped into the CPU's address space.

Access to the actual IOAPIC registers can be obtained by performing the following steps:

1. Write the number of the IOAPIC register to the address stored in IOREGSEL_REG
2. Read the value from / write the value to the address referred to by IOWIN_REG.

See also

IO-APIC manual