MACHINE_START与MACHINE_END

来源：互联网发布：湄公河大案泰国知乎编辑：程序博客网时间：2024/04/30 15:54

在移植Linux时，有个结构体需要填写，它以MACHINE_START开始并以MACHINE_END结束，如下mini2440开发板的移植为示例

[cpp]

view plain

copy

MACHINE_START(MINI2440, "MINI2440")
.phys_io = S3C2410_PA_UART,
.io_pg_offst = (((u32)S3C24XX_VA_UART) >> 18) & 0xfffc,
.boot_params = S3C2410_SDRAM_PA + 0x100,

.map_io = mini2440_map_io,
.init_machine = mini2440_init,

.init_irq = s3c24xx_init_irq,

.timer = &s3c24xx_timer,

MACHINE_END

其中MACHINE_START、MACHINE_END都是定义的宏，代码如下

[cpp]

view plain

copy

* Set of macros to define architecture features. This is built into

* a table by the linker.

#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 \

};

由上代码可知这两个宏一起定义了一个类型为struct machine_desc的变量，结构体定义如下

[cpp]

view plain

copy

struct machine_desc {

* Note! The first four elements are used

* by assembler code in head.S, head-common.S

unsigned int nr; /* architecture number */

unsigned int phys_io; /* start of physical io */

unsigned int io_pg_offst; /* byte offset for io

* page tabe entry */

const char *name; /* architecture name */

unsigned long boot_params; /* tagged list */

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

void (*init_irq)(void);

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

void (*init_machine)(void);

};

这个类型的变量放在内核代码段.arch.info.init中，在内核运行初期，被函数lookup_machine_type（此函数用汇编实现，在汇编文件中）取出，读取流程为

Start_kernel() -> setup_arch() -> setup_machine()-> lookup_machine_type()-------??没找到

在函数setup_machine()中，利用这个结构体类型的变量初始化一些全局变量，以备内核运行时使用，比如

init_arch_irq =mdesc->init_irq;

system_timer = mdesc->timer;

init_machine = mdesc->init_machine;

这个结构体中，成员init_machine保存的是开发板资源注册的初始化代码，init_irq保存的是中断初始化指针，timer保存的是一个struct sys_timer类型的指针…..如果我们要给自己的开发板定制内核，那么我们必须自己实现以上成员函数，其中函数init_machine()是我们向内核传递开发板设备信息的重要的常规途径，分析mini2440开发板内核移植代码知道，在这个函数中，注册了开发板所用到的所有设备的相关硬件信息！

[cpp]

view plain

copy

static void __init mini2440_init(void)

{

struct mini2440_features_t features = { 0 };

int i;

printk(KERN_INFO "MINI2440: Option string mini2440=%s\n",

mini2440_features_str);

/* Parse the feature string */

mini2440_parse_features(&features, mini2440_features_str);

/* turn LCD on */

s3c_gpio_cfgpin(S3C2410_GPC(0), S3C2410_GPC0_LEND);

/* Turn the backlight early on */

WARN_ON(gpio_request(S3C2410_GPG(4), "backlight"));

gpio_direction_output(S3C2410_GPG(4), 1);

/* remove pullup on optional PWM backlight -- unused on 3.5 and 7"s */

s3c_gpio_setpull(S3C2410_GPB(1), S3C_GPIO_PULL_UP);

s3c2410_gpio_setpin(S3C2410_GPB(1), 0);

s3c_gpio_cfgpin(S3C2410_GPB(1), S3C2410_GPIO_INPUT);

/* Make sure the D+ pullup pin is output */

WARN_ON(gpio_request(S3C2410_GPC(5), "udc pup"));

gpio_direction_output(S3C2410_GPC(5), 0);

/* mark the key as input, without pullups (there is one on the board) */

for (i = 0; i < ARRAY_SIZE(mini2440_buttons); i++) {

s3c_gpio_setpull(mini2440_buttons[i].gpio, S3C_GPIO_PULL_UP);

s3c_gpio_cfgpin(mini2440_buttons[i].gpio, S3C2410_GPIO_INPUT);

}

if (features.lcd_index != -1) {

int li;

mini2440_fb_info.displays =

&mini2440_lcd_cfg[features.lcd_index];

printk(KERN_INFO "MINI2440: LCD");

for (li = 0; li < ARRAY_SIZE(mini2440_lcd_cfg); li++)

if (li == features.lcd_index)

printk(" [%d:%dx%d]", li,

mini2440_lcd_cfg[li].width,

mini2440_lcd_cfg[li].height);

else

printk(" %d:%dx%d", li,

mini2440_lcd_cfg[li].width,

mini2440_lcd_cfg[li].height);

printk("\n");

s3c24xx_fb_set_platdata(&mini2440_fb_info);

}

s3c24xx_udc_set_platdata(&mini2440_udc_cfg);

s3c24xx_mci_set_platdata(&mini2440_mmc_cfg);
s3c_nand_set_platdata(&mini2440_nand_info);
s3c_i2c0_set_platdata(NULL);

i2c_register_board_info(0, mini2440_i2c_devs,

ARRAY_SIZE(mini2440_i2c_devs));

platform_add_devices(mini2440_devices, ARRAY_SIZE(mini2440_devices));

if (features.count) /* the optional features */
platform_add_devices(features.optional, features.count);

}

那么成员函数init_machine什么时候被调用呢？

在函数setup_machine()中有一条语句init_machine =mdesc->init_machine;其中init_machine为全局函数指针变量，此变量在函数customize_machine()中被调用,代码如下所示：

[cpp]

view plain

copy

static int __init customize_machine(void)

{

/* customizes platform devices, or adds new ones */

if (init_machine)

init_machine();

return 0;

}

arch_initcall(customize_machine);

在MACHINE_START与MACHINE_END之间还要填写一些参数，参照结构体注释小心填写即可，最好找个例子参考参考。

源文档 <http://blog.csdn.net/cxw3506/article/details/8475965>

0 0