IRQ context handling

API for handling IRQ contexts More...

Data Structures
struct	irq_context_t
	Architecture-specific structure for holding the processor state. More...

Macros
#define	REG_BYTE_CNT   256
	The number of bytes required to save thread context.

Functions
static void	irq_create_context (irq_context_t *context, uintptr_t stack_pointer, uintptr_t routine, const uintptr_t *args)
	Fill a newly allocated context block.
static void	irq_set_context (irq_context_t *cxt)
	Switch out contexts (for interrupt return).
static irq_context_t *	irq_get_context (void)
	Get the current IRQ context.

Register Accessors
Convenience macros for accessing context registers
#define	CONTEXT_PC(c)
	Fetch the program counter from an irq_context_t.
#define	CONTEXT_FP(c)
	Fetch the frame pointer from an irq_context_t.
#define	CONTEXT_SP(c)
	Fetch the stack pointer from an irq_context_t.
#define	CONTEXT_RET(c)
	Fetch the return value from an irq_context_t.

Detailed Description

API for handling IRQ contexts

Thread execution state and accessors

This API provides functions to create a new IRQ context, get a pointer to the current context, or set the context that will be used when returning from an exception.

This API includes the structure and accessors for a thread's context state, which contains the registers that are stored and loaded upon thread context switches, which are passed back to interrupt handlers.

Macro Definition Documentation

CONTEXT_FP

#define CONTEXT_FP

(

c

)

Value:

((c).r[14])

Fetch the frame pointer from an irq_context_t.

Parameters

c	The context to read from.

Returns

The frame pointer value.

CONTEXT_PC

#define CONTEXT_PC

(

c

)

Value:

((c).pc)

Fetch the program counter from an irq_context_t.

Parameters

c	The context to read from.

Returns

The program counter value.

Referenced by catchnull(), and on_break().

CONTEXT_RET

#define CONTEXT_RET

(

c

)

Value:

((c).r[0])

Fetch the return value from an irq_context_t.

Parameters

c	The context to read from.

Returns

The return value.

CONTEXT_SP

#define CONTEXT_SP

(

c

)

Value:

((c).r[15])

Fetch the stack pointer from an irq_context_t.

Parameters

c	The context to read from.

Returns

The stack pointer value.

REG_BYTE_CNT

#define REG_BYTE_CNT   256

The number of bytes required to save thread context.

This should include all general CPU registers, FP registers, and status regs (even if not all of these are actually used).

Note

On the Dreamcast, we need 228 bytes for all of that, but we round it up to a nicer number for sanity.

Function Documentation

irq_create_context()

static void irq_create_context ( irq_context_t * context, uintptr_t stack_pointer, uintptr_t routine, const uintptr_t * args )

inlinestatic

Fill a newly allocated context block.

The given parameters will be passed to the called routine (up to the architecture maximum). For the Dreamcast, this maximum is 4.

Parameters

context	The IRQ context to fill in.
stack_pointer	The value to set in the stack pointer.
routine	The address of the program counter for the context.
args	Any arguments to set in the registers. This cannot be NULL, and must have enough values to fill in up to the architecture maximum.

References arch_irq_create_context().

irq_get_context()

static irq_context_t * irq_get_context ( void )

inlinestatic

Get the current IRQ context.

This will fetch the processor context prior to the exception handling during an IRQ service routine.

Returns

The current IRQ context.

See also

irq_set_context()

References arch_irq_get_context().

irq_set_context()

static void irq_set_context ( irq_context_t * cxt )

inlinestatic

Switch out contexts (for interrupt return).

This function will set the processor state that will be restored when the exception returns.

Parameters

cxt	The IRQ context to restore.

See also

irq_get_context()

References arch_irq_set_context(), and cxt.