Architecture

Dreamcast Architecture-Specific Options and high-level API More...

Topics
	Byte Order
	Byte-order management for the SH4 architecture
	Console Types
	Byte values returned by hardware_sys_mode()
	Exit Paths
	Potential exit paths from the kernel on arch_exit()
	Memory Capacity
	Console memory sizes
	Region Codes
	Values returned by hardware_sys_mode();

Files
file	arch.h
	Dreamcast architecture specific options.

Macros
#define	_arch_mem_top   ((uint32) 0x8d000000)
	Top of memory available, depending on memory size.
#define	PAGESIZE   4096
	Page size (for MMU)
#define	PAGESIZE_BITS   12
	Bits for page size.
#define	PAGEMASK   (PAGESIZE - 1)
	Mask for page offset.
#define	page_count   ((_arch_mem_top - page_phys_base) / PAGESIZE)
	Page count "variable".
#define	page_phys_base   0x8c010000
	Base address of available physical pages.
#define	THD_SCHED_HZ   100
	Scheduler interrupt frequency.
#define	ELF_SYM_PREFIX   "_"
	Global symbol prefix in ELF files.
#define	ELF_SYM_PREFIX_LEN   1
	Length of global symbol prefix in ELF files.
#define	ARCH_NAME   "Dreamcast"
	Standard name for this arch.
#define	ARCH_ELFCLASS   ELFCLASS32
	ELF class for this architecture.
#define	ARCH_ELFDATA   ELFDATA2LSB
	ELF data encoding for this architecture.
#define	ARCH_CODE   EM_SH
	ELF machine type code for this architecture.
#define	HW_MEMSIZE   (_arch_mem_top - 0x8c000000)
	Determine how much memory is installed in current machine.
#define	DBL_MEM   (_arch_mem_top - 0x8d000000)
	Use this macro to easily determine if system has 32MB of RAM.

Functions
static const unsigned	HZ ("Please use the new THD_SCHED_HZ macro.")
	Legacy symbol for scheduler frequency.
void	arch_panic (const char *str) __noreturn
	Panic function.
void	arch_main (void) __noreturn
	Kernel C-level entry point.
void	arch_set_exit_path (int path)
	Set the exit path.
void	arch_exit (void) __noreturn
	Generic kernel "exit" point.
void	arch_return (int ret_code) __noreturn
	Kernel "return" point.
void	arch_abort (void) __noreturn
	Kernel "abort" point.
void	arch_reboot (void) __noreturn
	Kernel "reboot" call.
void	arch_menu (void) __noreturn
	Kernel "exit to menu" call.
int	mm_init (void)
	Initialize the memory management system.
void *	mm_sbrk (unsigned long increment)
	Request more core memory from the system.
int	hardware_sys_init (void)
	Initialize bare-bones hardware systems.
int	hardware_periph_init (void)
	Initialize some peripheral systems.
void	hardware_shutdown (void)
	Shut down hardware that was initted.
int	hardware_sys_mode (int *region)
	Retrieve the system mode of the console in use.
static void	arch_sleep (void)
	Dreamcast specific sleep mode function.
static bool	arch_valid_address (uintptr_t ptr)
	Returns true if the passed address is likely to be valid.
static bool	arch_valid_text_address (uintptr_t ptr)
	Returns true if the passed address is in the text section of your program.

Variables
char	_executable_start
	Start and End address for .text portion of program.
char	_etext

Detailed Description

Dreamcast Architecture-Specific Options and high-level API

Macro Definition Documentation

_arch_mem_top

#define _arch_mem_top   ((uint32) 0x8d000000)

Top of memory available, depending on memory size.

Referenced by arch_valid_address().

ARCH_CODE

#define ARCH_CODE   EM_SH

ELF machine type code for this architecture.

ARCH_ELFCLASS

#define ARCH_ELFCLASS   ELFCLASS32

ELF class for this architecture.

ARCH_ELFDATA

#define ARCH_ELFDATA   ELFDATA2LSB

ELF data encoding for this architecture.

ARCH_NAME

#define ARCH_NAME   "Dreamcast"

Standard name for this arch.

DBL_MEM

#define DBL_MEM   (_arch_mem_top - 0x8d000000)

Use this macro to easily determine if system has 32MB of RAM.

Returns

Non-zero if console has 32MB of RAM, zero otherwise

ELF_SYM_PREFIX

#define ELF_SYM_PREFIX   "_"

Global symbol prefix in ELF files.

ELF_SYM_PREFIX_LEN

#define ELF_SYM_PREFIX_LEN   1

Length of global symbol prefix in ELF files.

HW_MEMSIZE

#define HW_MEMSIZE   (_arch_mem_top - 0x8c000000)

Determine how much memory is installed in current machine.

Returns

The total size of system memory in bytes.

page_count

#define page_count   ((_arch_mem_top - page_phys_base) / PAGESIZE)

Page count "variable".

The number of pages is static, so we can optimize this quite a bit.

page_phys_base

#define page_phys_base   0x8c010000

Base address of available physical pages.

PAGEMASK

#define PAGEMASK   (PAGESIZE - 1)

Mask for page offset.

PAGESIZE

#define PAGESIZE   4096

Page size (for MMU)

PAGESIZE_BITS

#define PAGESIZE_BITS   12

Bits for page size.

THD_SCHED_HZ

#define THD_SCHED_HZ   100

Scheduler interrupt frequency.

Timer interrupt frequency for the KOS thread scheduler.

Note

This value is what KOS uses initially upon startup, but it can be reconfigured at run-time.

See also

thd_get_hz(), thd_set_hz()

Function Documentation

arch_abort()

void arch_abort

(

void

)

Kernel "abort" point.

Note

This function will never return!

arch_exit()

void arch_exit

(

void

)

Generic kernel "exit" point.

Note

This function will never return!

arch_main()

void arch_main

(

void

)

Kernel C-level entry point.

Note

This function will never return!

arch_menu()

void arch_menu

(

void

)

Kernel "exit to menu" call.

Note

This function will never return!

arch_panic()

void arch_panic

(

const char *

str

)

Panic function.

This function will cause a kernel panic, printing the specified message.

Parameters

str	The error message to print.

Note

This function will never return!

arch_reboot()

void arch_reboot

(

void

)

Kernel "reboot" call.

Note

This function will never return!

arch_return()

void arch_return

(

int

ret_code

)

Kernel "return" point.

Note

This function will never return!

arch_set_exit_path()

void arch_set_exit_path

(

int

path

)

Set the exit path.

The default, if you don't call this, is ARCH_EXIT_RETURN.

Parameters

path	What arch_exit() should do.

See also

Exit Paths

arch_sleep()

static void arch_sleep ( void )

inlinestatic

Dreamcast specific sleep mode function.

arch_valid_address()

static bool arch_valid_address ( uintptr_t ptr )

inlinestatic

Returns true if the passed address is likely to be valid.

Doesn't have to be exact, just a sort of general idea.

Returns

Whether the address is valid or not for normal memory access.

References _arch_mem_top.

arch_valid_text_address()

static bool arch_valid_text_address ( uintptr_t ptr )

inlinestatic

Returns true if the passed address is in the text section of your program.

Returns

Whether the address is valid or not for text memory access.

References _etext, and _executable_start.

hardware_periph_init()

int hardware_periph_init

(

void

)

Initialize some peripheral systems.

This will be done automatically for you on start by the default arch_main(), so you shouldn't have to deal with this yourself.

Return values

0	On success (no error conditions defined).

hardware_shutdown()

void hardware_shutdown

(

void

)

Shut down hardware that was initted.

This function will shut down anything initted with hardware_sys_init() and hardware_periph_init(). This will be done for you automatically by the various exit points, so you shouldn't have to do this yourself.

hardware_sys_init()

int hardware_sys_init

(

void

)

Initialize bare-bones hardware systems.

This will be done automatically for you on start by the default arch_main(), so you shouldn't have to deal with this yourself.

Return values

0	On success (no error conditions defined).

hardware_sys_mode()

int hardware_sys_mode

(

int *

region

)

Retrieve the system mode of the console in use.

This function retrieves the system mode register of the console that is in use. This register details the actual system type in use (and in some system types the region of the device).

Parameters

region

On return, the region code (one of the Region Codes) of the device if the console type allows reading it through the system mode register – otherwise, you must retrieve the region from the flashrom.

Returns

The console type (one of the Console Types).

Note

Do not use before hardware_sys_init() has been called.

HZ()

static const unsigned HZ ( "Please use the new THD_SCHED_HZ macro." )

static

Legacy symbol for scheduler frequency.

Deprecated

See also

THD_SCHED_HZ

mm_init()

int mm_init

(

void

)

Initialize the memory management system.

Return values

0	On success (no error conditions defined).

mm_sbrk()

void * mm_sbrk

(

unsigned long

increment

)

Request more core memory from the system.

Parameters

increment

The number of bytes requested.

Returns

A pointer to the memory.

Note

This function will panic if no memory is available.

Variable Documentation

_etext

char _etext

extern

Referenced by arch_valid_text_address().

_executable_start

char _executable_start

extern

Start and End address for .text portion of program.

Referenced by arch_valid_text_address().