转自：http://blog.feedwhy.com.cn/s/blog_753fd0b00100t8js.html
在友善mini2440提供的linux2.6.32.2内核中，有如下定义：
MACHINE_START(MINI2440, "FriendlyARM Mini2440 development board").phys_io = S3C2410_PA_UART,.io_pg_offst = (((u32)S3C24XX_VA_UART) 18) 0xfffc,.boot_params = S3C2410_SDRAM_PA + 0x100,.init_irq = s3c24xx_init_irq,.map_io = mini2440_map_io,.init_machine= mini2440_machine_init,.timer = s3c24xx_timer,MACHINE_END下面分析一下：在include/asm-arm/mach/arch.h中，有定义#defineMACHINE_START(_type,_name)static const structmachine_desc __mach_desc_##_type__used__attribute__((__section__(".arch.info.init"))) = {.nr= MACH_TYPE_##_type,.name= _name,#defineMACHINE_END列出machine_desc的定义：structmachine_desc {unsigned int nr;unsigned int phys_io;unsigned int io_pg_offst;const char *name;unsigned long boot_params;unsigned int video_start;unsigned int video_end;unsigned int reserve_lp0 :1;unsigned int reserve_lp1 :1;unsigned int reserve_lp2 :1;unsigned int soft_reboot :1;void (*fixup)(structmachine_desc *,struct tag *, char **,struct meminfo *);void (*map_io)(void);void (*init_irq)(void);struct sys_timer *timer;void (*init_machine)(void);__attribute__((__section__(".arch.info.init"))) = {.nr= MACH_TYPE_MINI2440,.,.phys_io = S3C2410_PA_UART,.io_pg_offst = (((u32)S3C24XX_VA_UART) 18) 0xfffc,.boot_params = S3C2410_SDRAM_PA + 0x100,.init_irq = s3c24xx_init_irq,.map_io = mini2440_map_io,.init_machine= mini2440_machine_init,.timer = s3c24xx_timer,
MACH_TYPE_MINI2440 是mini2440开发板在linux中的机器号。"FriendlyARM Mini2440 development board"是开发板信息，在终端输入cat /proc/cpuinfo可以查看。MACHINE_START主要是定义了"structmachine_desc"的类型，放在 section(".arch.info.init")，是初始化数据，Kernel 起来之后将被丢弃。其余各个成员函数在setup_arch()中被赋值到内核结构体，在不同时期被调用：1. .init_machine在 arch/arm/kernel/setup.c 中被 customize_machine调用，放在 arch_initcall() 段里面，会自动按顺序被调用。static int __init customize_machine(void)
{
if (init_machine)
init_machine();
return 0;
}
arch_initcall(customize_machine);2. .init_irq在start_kernel()(文件init/main.c)-- init_IRQ() (在文件arch/arm/kernel/Irq.c)-- init_arch_irq()中被调用3. .map_io 在 setup_arch( command_line) (在文件arch/arm/kernel/setup.c)-- paging_init()(在文件arch/arm/kernel/mm/Mmu.c) -- devicemaps_init()(在文件arch/arm/kernel/mm/Mmu.c)中被调用4. .timer是定义系统时钟，定义TIMER4为系统时钟，在arch/arm/plat-s3c/time.c中体现。在start_kernel() -- time_init()(在文件arch/arm/kernel/Time.c)中被调用。5. .boot_params是bootloader向内核传递的参数的位置，这要和bootloader中参数的定义要一致。其他主要都在 setup_arch() 中用到。