在linux-2.6.28.2/arch/arm/mach-s3c2410/mach-smdk2410.c文件最后,有如下宏定义:
MACHINE_START(SMDK2410, "SMDK2410") /* @TODO: request a new identifier and switch
* to SMDK2410 */
/* Maintainer: Jonas Dietsche */
.phys_io = S3C2410_PA_UART,
.io_pg_offst = (((u32)S3C24XX_VA_UART) >> 18) & 0xfffc,
.boot_params = S3C2410_SDRAM_PA + 0x100,
.map_io = smdk2410_map_io,
.init_irq = s3c24xx_init_irq,
.init_machine = smdk2410_init,
.timer = &s3c24xx_timer,
MACHINE_END
而MACHINE_START和MACHINE_END宏定义在arch/arm/include/asm/mach/arch.h,如下:
#define MACHINE_START(_type,_name) \
static const struct machine_desc __mach_desc_##_type \
__used \
__attribute__((__section__(".arch.info.init"))) = { \
.nr = MACH_TYPE_##_type, \
.name = _name,
#define MACHINE_END \
};
将前面定义的MACHINE_START和MACHINE_END展开后得到:
static const struct machine_desc __mach_desc_SMDK2410
__attribute_used__
__attribute__((__section__(".arch.info.init"))) = {
.nr = MACH_TYPE_SMDK2410, /* architecture number */
.name = "SMDK2410", /* architecture name */
/* Maintainer: Jonas Dietsche */
.phys_io = S3C2410_PA_UART, /* start of physical io */
.io_pg_offst = (((u32)S3C24XX_VA_UART) >> 18) & 0xfffc,
.boot_params = S3C2410_SDRAM_PA + 0x100, /* tagged list */
.map_io = smdk2410_map_io, /* IO mapping function */
.init_irq = s3c24xx_init_irq,
.init_machine = smdk_machine_init,
.timer = &s3c24xx_timer,
}
MACH_TYPE_SMDK2410定义在arch/include/asm-arm/mach-types.h内,值为193.
/* arch/include/asm-arm/mach-types.h */
#define MACH_TYPE_SMDK2410 193
这个值是机器的类型值,编译时由arch/arm/tool/mach- types里面定义的数据生成的。
/* arch/arm/tool/mach-types */
smdk2410 ARCH_SMDK2410 SMDK2410 193
由上发现,MACHINE_START主要是定义了"struct machine_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。
kernel boot 起来的时候期望 bootloader 传参数进来,其中包括 Machine
Type,参考arch/arm/tools/mach-types 和MACHINE_START() 第一个参数对上号。因此,哪个MACHINE 是
run-time 的时候决定的,this way, you can pack as many machine as you want, and
dynamically initialize the specific platforms.
各个成员函数在不同时期被调用:
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。
2. init_irq在start_kernel() --> init_IRQ() --> init_arch_irq() 被调用
3. map_io 在 setup_arch() --> paging_init() --> devicemaps_init()被调用
其他主要都在 setup_arch() 中用到。
zz http://hi.baidu.com/kkernel/blog/item/48daf0d16237f0df562c844d.html
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