一、uboot存儲方式：

uboot源碼：二進制的uboot程序

0xffffffff：uboot分區沒有用的空閑空間

uboot環境變量：bootdelay、bootcmd、bootargs等參數，鍵與值用0x3d，即“=”隔開，兩參數之間用0x00，即\0隔開

0x00000000：uboot參數分區沒有用的空閑空間

二、uboot參數操作：

2.1 參數：

include/configs/xxx.h　　//xxx為芯片名稱

中定義了一些環境變量默認值的宏定義

common/env_embedded.c

中定義了環境變量鍵值對字符串結構體

2.2 功能函數：

common/env_common.c

初始化如下結構：

#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 功能函數調用

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、內核查參方式：

3.1 mtd方式

文件形式，待補

3.2 ioremap

驅動+應用，待補

3.3 mtd_debug

軟件移植，待補

3.4 fw_printenv

3.4.1 工具生成方法：

uboot_source_tree # make ARCH=arm CROSS_COMPILE=arm-linux-gcc env

uboot_source_tree/tools/env下得到fw_printenv與fw_env.config

3.4.2 將工具與配置文件放到板子文件系統上

3.4.3 修改fw_env.config

Device offset 　　?對應于uboot源碼目錄中include/configs/board_name.h的CONFIG_ENV_OFFSET

Env size　　　　　對應于uboot源碼目錄中include/configs/board_name.h的CONFIG_ENV_SIZE

Flash sector size ?對應于uboot源碼目錄中include/configs/board_name.h的CONFIG_ENV_SECT_SIZE

Number of sectors對應于多少塊 這里用的是nand flash，如果用nor就不用寫這個了

3.4.4 使用方法：

ln -s fw_printenv fw_setenv

讀：

fw_printenv 讀全參

fw_printenv -n param_name 讀指定參

寫：

fw_setenv?param_name param_value 寫指定參

3.4.5 錯誤解決辦法：

錯誤A:/include/linux/types.h:154:36: error: conflicting types for ‘uintmax_t’?typedef u_int32_t uintmax_t;

arm-linux/target/usr/include/stdint.h:140:32: note: previous declaration of ‘uintmax_t’ was here

typedef unsigned long long int uintmax_t;

解決A：兩個文件的uintmax_t類型沖突了，將uboot中的類型按照編譯器文件中的類型改過來

錯誤B：include/linux/types.h:155:36: error: conflicting types for ‘intmax_t’?typedef int32_t intmax_t;

arm-linux/target/usr/include/stdint.h:138:24: note: previous declaration of ‘intmax_t’ was here

typedef long long int intmax_t;

解決B：方法同上

錯誤C:Warning: Bad CRC, using default environment

解決C:方案一、環境變量沒save，uboot的環境變量分散于代碼中，只有save才會存儲與env地址中，如果不存到env地址中，fw_printenv是找不到的

方案二、fw_env.config沒設置參數，參數設置方法見3.4.3

四、uboot增加環境變量

4.1 方法一、uboot命令行手動set param_name param_value

4.2 方法二、uboot代碼中添加：

1）uboot源碼目錄中include/configs/board_name.h添加變量宏定義

2）uboot源碼目錄中common/env_common.c添加

?