本文讲解LINUX中用MACHINE_START/MACHINE_END定义的MACH,并给出定义的各个成员函数在初始化过程中被调用的时机。
1. 定义一个MACH
LINUX中MACHINE定义是用MACHINE_START()/MACHINE_END两个宏来实现的,比如MSM的实现(arch/arm/mach-msm/board-halibut.c):
- MACHINE_START(HALIBUT,"Halibut Board (QCT SURF7200A)")
- .boot_params = 0x10000100,
- .map_io = halibut_map_io,
- .init_irq = halibut_init_irq,
- .init_machine = halibut_init,
- .timer = &msm_timer,
- MACHINE_END
- MACHINE_START(HALIBUT,"Halibut Board (QCT SURF7200A)")
- .boot_params = 0x10000100,
- .map_io = halibut_map_io,
- .init_irq = halibut_init_irq,
- .init_machine = halibut_init,
- .timer = &msm_timer,
- MACHINE_END
2. MACHINE_START / MACHINE_END定义
上面的定义中,用到了这两个宏MACHINE_START/MACHINE_END,下面是它们具体的定义(在arch/arm/include/asm/mach/arch.h中):
- #defineMACHINE_START(_type,_name) \
- static const structmachine_desc __mach_desc_##_type \
- __used \
- __attribute__((__section__(".arch.info.init")))= { \
- .nr = MACH_TYPE_##_type, \
- .name = _name,
-
- #define MACHINE_END \
- };
- #defineMACHINE_START(_type,_name) \
- static const structmachine_desc __mach_desc_##_type \
- __used \
- __attribute__((__section__(".arch.info.init")))= { \
- .nr = MACH_TYPE_##_type, \
- .name = _name,
-
- #define MACHINE_END \
- };
struct machine_desc也是定义在arch/arm/include/asm/mach/arch.h
- struct machine_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)(struct machine_desc *,
- struct tag *, char **,
- struct meminfo *);
- void (*map_io)(void);
- void (*init_irq)(void);
- struct sys_timer *timer;
- void (*init_machine)(void);
- };
- struct machine_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)(struct machine_desc *,
- struct tag *, char **,
- struct meminfo *);
- void (*map_io)(void);
- void (*init_irq)(void);
- struct sys_timer *timer;
- void (*init_machine)(void);
- };
3. MACH HALIBUT的定义
把1中定义的MACH展开之后,得到:
- struct machine_desc __mach_desc_HALIBUT{
- __used
- __attribute__((__section__(".arch.info.init")))= {
- .nr = MACH_TYPE_HALIBUT,
- .name = "HalibutBoard (QCT SURF7200A)",
- .boot_params = 0x10000100,
- .map_io = halibut_map_io,
- .init_irq = halibut_init_irq,
- .init_machine = halibut_init,
- .timer = &msm_timer,
- };
- struct machine_desc __mach_desc_HALIBUT{
- __used
- __attribute__((__section__(".arch.info.init")))= {
- .nr = MACH_TYPE_HALIBUT,
- .name = "HalibutBoard (QCT SURF7200A)",
- .boot_params = 0x10000100,
- .map_io = halibut_map_io,
- .init_irq = halibut_init_irq,
- .init_machine = halibut_init,
- .timer = &msm_timer,
- };
总结一下: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。
4. 成员函数被调用的时机
在setup_arch() [setup.c#758~760]中init_irq, timer & init_machine分别被赋值给下列变量:
init_arch_irq = mdesc->init_irq;
system_timer = mdesc->timer;
init_machine = mdesc->init_machine;
而这三个函数指针是在下列场景中被调用的:
1) start_kernel()[main.c#589]-> init_IRQ() [irq.c] ->init_arch_irq();
2) start_kernel()[main.c#595]->time_init () [time.c] ->system_time->init();
3) customize_machine()[setup.c#692] -> init_machine();
customize_machine是被放在arch_initcall段的,按照顺序被调用。xxx_initcall段内的函数是按下列顺序被调用的:start_kernel() [main.c#682] -> rest_init()
[启动内核线程]-> kernel_init() –> do_basic_setup()-> do_initcalls();
map_io是在下列顺序中被调用
4) start_kernel()[main.c#546]-> setup_arch () [setup.c#745] -> paging_init() [mmu.c#1028] -> devicemaps_init()[mmu.c#993] -> map_io()
从它们在start_kernel()中被调用的顺序,可知它们执行的先后为:map_io; init_irq; timer->time_init; init_machine。
原文:http://blog.csdn.net/myxmu/article/details/8015879
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