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 隔开
0x00000000：uboot参数分区没有用的空闲空间
二、uboot参数操作：
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：
3.1 mtd方式
文件形式，待补
3.2 ioremap
驱动+应用，待补
3.3 mtd_debug
软件移植，待补
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与fw_env.config
3.4.2 将工具与配置文件放到板子文件系统上
3.4.3 修改fw_env.config
Device offset 对应于uboot源码目录中include/configs/board_name.h的CONFIG_ENV_OFFSET
Env size 对应于uboot源码目录中include/configs/board_name.h的CONFIG_ENV_SIZE
Flash sector size 对应于uboot源码目录中include/configs/board_name.h的CONFIG_ENV_SECT_SIZE
Number of sectors对应于多少块 这里用的是nand flash，如果用nor就不用写这个了
3.4.4 使用方法：
ln -s fw_printenv fw_setenv
读：
fw_printenv 读全参
fw_printenv -n param_name 读指定参
写：
fw_setenv param_name param_value 写指定参
3.4.5 错误解决办法：
错误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;
解决A：两个文件的uintmax_t类型冲突了，将uboot中的类型按照编译器文件中的类型改过来
错误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;
解决B：方法同上
错误C:Warning: Bad CRC, using default environment
解决C:方案一、环境变量没save，uboot的环境变量分散于代码中，只有save才会存储与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没设置参数，参数设置方法见3.4.3
四、uboot增加环境变量
4.1 方法一、uboot命令行手动set param_name param_value
4.2 方法二、uboot代码中添加：
1）uboot源码目录中include/configs/board_name.h添加变量宏定义
2）uboot源码目录中common/env_common.c添加
