DonGYonG

Overview

MACHINE_START(xxxxx)
    .map_io = xxx,
    .reserve = xxx,
    .init_irq = xxx,
    .handle_irq = xxx,
    .timer = xxx,
    .init_machine = xxx,
    .init_early = xxx,
    .init_very_early = xxx,
    .restart = xxx,
MACHINE_END

Calling sequence

MACHINE_START

Defined in :

arch/arm/include/asm/mach/arch.h

Calling sequence

init_machine

start_kernel()--->setup_arch()
          --->rest_init--->kernel_init(){kernel_thread}
                            --->do_basic_setup--->
                                --->do_initcalls()
                                    --->customize_machine(){__initcall3_start}--->.init_machine

• start_kernel()

  /init/main.c

• setup_arch()

/arch/arm/kernel/setup.c

void __init setup_arch(char **cmdline_p)
{
    struct machine_desc *mdesc;

    setup_processor();
    mdesc = setup_machine_fdt(__atags_pointer);
    if (!mdesc)
        mdesc = setup_machine_tags(machine_arch_type);
    machine_desc = mdesc;
    machine_name = mdesc->name;

• setup_machine_fdt

• setup_machine_fdt - Machine setup when an dtb was passed to the kernel
• @dt_phys: physical address of dt blob *
• If a dtb was passed to the kernel in r2, then use it to choose the
• correct machine_desc and to setup the system. */

• customize_machine

    static int __init customize_machine(void)
    {
        /* customizes platform devices, or adds new ones */
        if (machine_desc->init_machine)
            machine_desc->init_machine();
        return 0;
    }
  
    arch\_initcall(customize_machine);
  
    #define arch_initcall(fn)               __define_initcall("3",fn,3)
  
        #define __define_initcall(level,fn) \
        static initcall_t __initcall_##fn __used \
        __attribute__((__section__(".initcall" level ".init"))) = fn
  
  
    /* initcalls are now grouped by functionality into separate 
     * subsections. Ordering inside the subsections is determined
     * by link order. 
     * For backwards compatibility, initcall() puts the call in 
     * the device init subsection.
     *
     * The `id' arg to __define_initcall() is needed so that multiple initcalls
     * can point at the same handler without causing duplicate-symbol build errors.
     */
  

• do_initcalls

    Main.c (init)   22012   11/26/2012
  
    static void __init do_initcalls(void)
    {
        int level;
  
        for (level = 0; level < ARRAY_SIZE(initcall_levels) - 1; level++)
            do_initcall_level(level);
    }
  

init_early

start_kernel()--->setup_arch()--->init_very_early()

called in

    /arch/arm/kernel/setup.c



    void __init setup_arch(char **cmdline_p)
    {
        struct machine_desc *mdesc;

        setup_processor();
        mdesc = setup_machine_fdt(__atags_pointer);
        if (!mdesc)
            mdesc = setup_machine_tags(machine_arch_type);
        machine_desc = mdesc;
        machine_name = mdesc->name;

        setup_dma_zone(mdesc);

        if (mdesc->restart_mode)
            reboot_setup(&mdesc->restart_mode);

        if (mdesc->init_very_early)
            mdesc->init_very_early();

        sanity_check_meminfo();
        arm_memblock_init(&meminfo, mdesc);

        paging_init(mdesc);
        request_standard_resources(mdesc);

        if (mdesc->restart)
            arm_pm_restart = mdesc->restart;


    #ifdef CONFIG_MULTI_IRQ_HANDLER
        handle_arch_irq = mdesc->handle_irq;
    #endif

    #ifdef CONFIG_VT
    #if defined(CONFIG_VGA_CONSOLE)
        conswitchp = &vga_con;
    #elif defined(CONFIG_DUMMY_CONSOLE)
        conswitchp = &dummy_con;
    #endif
    #endif

        if (mdesc->init_early)
            mdesc->init_early();
    }

init_very_early

start_kernel()--->setup_arch()--->init_very_early()--->init_early()->

.reserve

start_kernel()--->setup_arch()
                --->init_very_early()
                --->arm_memblock_init->reserve
                --->paging_init->devicemaps_init->mdesc->map_io
                --->restart[mdesc->]
                --->handle_irq[mdesc->]
                --->init_early[mdesc->]

__init

definition

#define __init      __section(.init.text) __cold notrace
#define __initdata  __section(.init.data)
#define __initconst __section(.init.rodata)
#define __exitdata  __section(.exit.data)
#define __exit_call __used __section(.exitcall.exit)

These macros are used to mark some functions or initialized data (doesn't apply to uninitialized data) as `initialization' functions.

The kernel can take this as hint that the function is used only during the initialization phase and free up used memory resources after.

Usage

For functions:

You should add __init immediately before the function name, like:

 *
 * static void __init initme(int x, int y)
 * {
 *    extern int z; z = x * y;
 * }
 *

If the function has a prototype somewhere, you can also add __init between closing brace of the prototype and semicolon:

 * extern int initialize_foobar_device(int, int, int) __init;

For initialized data:

You should insert __initdata between the variable name and equal sign followed by value, e.g.:

 *
 * static int init_variable __initdata = 0;
 * static const char linux_logo[] __initconst = { 0x32, 0x36, ... };
 *

• Don't forget to initialize data not at file scope, i.e. within a function,
• as gcc otherwise puts the data into the bss section and not into the init
• section.
• Also note, that this data cannot be "const".

  Reference