machine_desc

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每一个machine，都要定义一个自己的machine_desc结构，该结构定义了该machine的一些最基本的特性。

struct machine_desc {

    unsigned int        nr;        /* architecture number    */

    const char        *name;        /* architecture name    */

    unsigned long        boot_params;    /* tagged list        */

    const char        **dt_compat;    /* array of device tree

                         * 'compatible' strings    */

    unsigned int        nr_irqs;    /* number of IRQs */

    unsigned int        video_start;    /* start of video RAM    */

    unsigned int        video_end;    /* end of video RAM    */

    unsigned int        reserve_lp0 :;    /* never has lp0    */

    unsigned int        reserve_lp1 :;    /* never has lp1    */

    unsigned int        reserve_lp2 :;    /* never has lp2    */

    unsigned int        soft_reboot :;    /* soft reboot        */

    void            (*fixup)(struct machine_desc *,

                     struct tag *, char **,

                     struct meminfo *);

    void            (*reserve)(void);/* reserve mem blocks    */

    void            (*map_io)(void);/* IO mapping function    */

    void            (*init_early)(void);

    void            (*init_irq)(void);

    struct sys_timer    *timer;        /* system tick timer    */

    void            (*init_machine)(void);

};

在arch/arm/include/asm/mach/arch.h中有下面的宏，用于声明处理器相关的machine_desc结构体，并将该结构体放入vmlinux.lds中指定的段中。

#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                \

};

在arch/arm/mach-s3c64xx/mach-smdk6410.c中使用上述宏声明machine_desc结构体，

MACHINE_START(SMDK6410, "SMDK6410")

    /* Maintainer: Ben Dooks <ben-linux@fluff.org> */

    //.phys_io    = S3C_PA_UART & 0xfff00000,

    //.io_pg_offst    = (((u32)S3C_VA_UART) >> 18) & 0xfffc,

    .boot_params    = S3C64XX_PA_SDRAM + 0x100,

    .init_irq    = s3c6410_init_irq,

    .map_io        = smdk6410_map_io,

    .init_machine    = smdk6410_machine_init,

    .timer        = &s3c24xx_timer,

MACHINE_END

上面的宏展开得到：

static const struct machine_desc __mach_desc_SMDK6410 __used    __attribute__((__section__(".arch.info.init"))) = {

    .nr        = MACH_TYPE_SMDK6410,

    .name        = "SMDK6410",

    .boot_params    = S3C64XX_PA_SDRAM + 0x100, //0x5000_0100

    .init_irq    = s3c6410_init_irq,

    .map_io        = smdk6410_map_io,

    .init_machine    = smdk6410_machine_init,

    .timer        = &s3c24xx_timer,

}

MACH_TYPE_SMDK6410在 arch/arm/tools/mach-types文件中定义

# machine_is_xxx CONFIG_xxxx 　　MACH_TYPE_xxx 　　number

1621：smdk6410 MACH_SMDK6410 SMDK6410 　　　　 1626

参考：linux3.1.0内核中/include/generated下mach-types.h的产生

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