machine_desc

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 :1;    /* never has lp0    */
    unsigned int        reserve_lp1 :1;    /* never has lp1    */
    unsigned int        reserve_lp2 :1;    /* never has lp2    */
    unsigned int        soft_reboot :1;    /* 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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