你了解Embeded linux中的Uboot参数与内核？_技术

一、uboot存储方式：

uboot源码：二进制的uboot程序

0xffffffff：uboot分区没有用的空闲空间

uboot环境变量：bootdelay、bootcmd、bootargs等参数，键与值用0x3d，即“=”隔开，两参数之间用0x00，即\0隔开

0x00000000：uboot参数分区没有用的空闲空间

二、uboot参数 *** 作：

2.1 参数：

include/configs/xxx.h　　//xxx为芯片名称

中定义了一些环境变量默认值的宏定义

common/env_embedded.c

中定义了环境变量键值对字符串结构体

2.2 功能函数：

common/env_common.c

初始化如下结构：

#ifdef CONFIG_ENV_IS_IN_NAND

extern int nand_env_init(void);
extern unsigned char nand_env_get_char_spec(int);
extern int nand_saveenv(void);
extern void nand_env_relocate_spec(void);

staTIc struct env_common_func_t nand_env_cmn_func = {
.env_init = nand_env_init,
.env_get_char_spec = nand_env_get_char_spec,
.saveenv = nand_saveenv,
.env_relocate_spec = nand_env_relocate_spec,
.env_name_spec = "NAND",
};

#else

staTIc struct env_common_func_t nand_env_cmn_func = {0};

#endif

#ifdef CONFIG_ENV_IS_IN_SPI_FLASH

extern int sf_env_init(void);
extern unsigned char sf_env_get_char_spec(int);
extern int sf_saveenv(void);
extern void sf_env_relocate_spec(void);

staTIc struct env_common_func_t nand_env_cmn_func = {
.env_init = sf_env_init,
.env_get_char_spec = sf_env_get_char_spec,
.saveenv = sf_saveenv,
.env_relocate_spec = sf_env_relocate_spec,
.env_name_spec = "SPI FLASH",
};

#else

staTIc struct env_common_func_t sf_env_cmn_func = {0};

#endif

#ifdef CONFIG_ENV_IS_IN_EMMC

extern int emmc_env_init(void);
extern unsigned char emmc_env_get_char_spec(int);
extern int emmc_saveenv(void);
extern void emmc_env_relocate_spec(void);

static struct env_common_func_t emmc_env_cmn_func = {
.env_init = emmc_env_init,
.env_get_char_spec = emmc_env_get_char_spec,
.saveenv = emmc_saveenv,
.env_relocate_spec = emmc_env_relocate_spec,
.env_name_spec = "NAND",
};

#else

static struct env_common_func_t emmc_env_cmn_func = {0};

#endif

int env_init(void)
{
switch (get_boot_media())

{
default:
env_cmn_func = NULL;
break;
case BOOT_MEDIA_NAND:
env_cmn_func = &nand_env_cmn_func;
break;
case BOOT_MEDIA_SPIFLASH:
env_cmn_func = &sf_env_cmn_func;
break;
case BOOT_MEDIA_EMMC:
env_cmn_func = &emmc_env_cmn_func;
break;
case BOOT_MEDIA_DDR:
env_cmn_func = &sf_env_cmn_func;
break;
}

if (env_cmn_func && !env_cmn_func->env_name_spec)

env_cmn_func = NULL;

if (!env_cmn_func)
return -1;

env_cmn_func->env_init();
env_name_spec = env_cmn_func->env_name_spec;

return 0;
}

2.3 功能函数调用

common/cmd_nvedit.c

U_BOOT_CMD(
saveenv, 1, 0, do_saveenv,
"save environment variables to persistent storage",
""
);

int do_saveenv (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
{
extern char * env_name_spec;

env_crc_update ();

return (saveenv() ? 1 : 0);
}

三、内核查参方式：