System Initialization

Zephyr offers an infrastructure to call initialization code before main. More...

Data Structures
union	init_function
	Initialization function for init entries. More...
struct	init_entry
	Structure to store initialization entry information. More...

Macros
#define	INIT_LEVEL_ORD(level)
	Obtain the ordinal for an init level.
#define	SYS_INIT(init_fn, level, prio)    SYS_INIT_NAMED(init_fn, init_fn, level, prio)
	Register an initialization function.
#define	SYS_INIT_NAMED(name, init_fn_, level, prio)
	Register an initialization function (named).

Detailed Description

Zephyr offers an infrastructure to call initialization code before main.

Such initialization calls can be registered using SYS_INIT() or SYS_INIT_NAMED() macros. By using a combination of initialization levels and priorities init sequence can be adjusted as needed. The available initialization levels are described, in order, below:

• EARLY: Used very early in the boot process, right after entering the C domain (z_cstart()). This can be used in architectures and SoCs that extend or implement architecture code and use drivers or system services that have to be initialized before the Kernel calls any architecture specific initialization code.
• PRE_KERNEL_1: Executed in Kernel's initialization context, which uses the interrupt stack. At this point Kernel services are not yet available.
• PRE_KERNEL_2: Same as PRE_KERNEL_1.
• POST_KERNEL: Executed after Kernel is alive. From this point on, Kernel primitives can be used.
• APPLICATION: Executed just before application code (main).
• SMP: Only available if CONFIG_SMP is enabled, specific for SMP.

Initialization priority can take a value in the range of 0 to 99.

Note

The same infrastructure is used by devices.

Macro Definition Documentation

INIT_LEVEL_ORD

#define INIT_LEVEL_ORD

(

level

)

#include <zephyr/init.h>

Value:

        COND_CODE_1(Z_INIT_EARLY_##level, (Z_INIT_ORD_EARLY),                  \
        (COND_CODE_1(Z_INIT_PRE_KERNEL_1_##level, (Z_INIT_ORD_PRE_KERNEL_1),   \
        (COND_CODE_1(Z_INIT_PRE_KERNEL_2_##level, (Z_INIT_ORD_PRE_KERNEL_2),   \
        (COND_CODE_1(Z_INIT_POST_KERNEL_##level, (Z_INIT_ORD_POST_KERNEL),     \
        (COND_CODE_1(Z_INIT_APPLICATION_##level, (Z_INIT_ORD_APPLICATION),     \
        (COND_CODE_1(Z_INIT_SMP_##level, (Z_INIT_ORD_SMP),                     \
        (ZERO_OR_COMPILE_ERROR(0)))))))))))))

Obtain the ordinal for an init level.

Parameters

level

Init level (EARLY, PRE_KERNEL_1, PRE_KERNEL_2, POST_KERNEL, APPLICATION, SMP).

Returns

Init level ordinal.

SYS_INIT

#define SYS_INIT	(		init_fn,
			level,
			prio
	)		SYS_INIT_NAMED(init_fn, init_fn, level, prio)

#include <zephyr/init.h>

Register an initialization function.

The function will be called during system initialization according to the given level and priority.

Parameters

init_fn	Initialization function.
level	Initialization level. Allowed tokens: EARLY, PRE_KERNEL_1, PRE_KERNEL_2, POST_KERNEL, APPLICATION and SMP if CONFIG_SMP is enabled.
prio	Initialization priority within _level. Note that it must be a decimal integer literal without leading zeroes or sign (e.g. 32), or an equivalent symbolic name (e.g. #define MY_INIT_PRIO 32); symbolic expressions are not permitted (e.g. CONFIG_KERNEL_INIT_PRIORITY_DEFAULT + 5).

SYS_INIT_NAMED

#define SYS_INIT_NAMED	(		name,
			init_fn_,
			level,
			prio
	)

#include <zephyr/init.h>

Value:

        static const Z_DECL_ALIGN(struct init_entry)                                      \
                Z_INIT_ENTRY_SECTION(level, prio, 0) __used __noasan                      \
                Z_INIT_ENTRY_NAME(name) = {.init_fn = {.sys = (init_fn_)},                \
                        Z_INIT_SYS_INIT_DEV_NULL}

Register an initialization function (named).

Note

This macro can be used for cases where the multiple init calls use the same init function.

Parameters

name	Unique name for SYS_INIT entry.
init_fn_	See SYS_INIT().
level	See SYS_INIT().
prio	See SYS_INIT().

See also

SYS_INIT()