uboot 官方学习文档 http://www.denx.de/wiki/DULG/Manual
=> help setenv setenv - set environment variables Usage: setenv name value ... - set environment variable 'name' to 'value ...' setenv name - delete environment variable 'name' =>To modify the U-Boot environment you have to use the setenv command. When called with exactly one argument, it will delete any variable of that name from U-Boot's environment, if such a variable exists. Any storage occupied for such a variable will be automatically reclaimed: => setenv foo This is an example value. => printenv foo foo=This is an example value. => setenv foo => printenv foo ## Error: "foo" not defined =>U_BOOT_CMD_COMPLETE(
setenv, CONFIG_SYSlybq, 0, do_env_set,
"set environment variables",
"name value ...n"
" - set environment variable 'name' to 'value ...'n"
"setenv namen"
" - delete environment variable 'name'",
var_complete
);do_env_set() 如果uboot代码里面实现了saveenv，那么在setenv后，可以用saveenv去将所有的变量都存储起来。具体存到哪里，要根据是uboot中的定义决定。比如
#define CONFIG_ENV_IS_IN_SPI_flash 就是定义成存储环境变量到SPI Flash里面。#ifdef CONFIG_SPI_BOOT
#define CONFIG_ENV_OVERWRITE
#define CONFIG_ENV_IS_IN_SPI_FLASH
#define CONFIG_ENV_SECT_SIZE 0x10000
#define CONFIG_ENV_OFFSET 0x1f0000
#elif defined CONFIG_NAND_BOOT
#define CONFIG_CMD_SAVEENV
#define CONFIG_ENV_OVERWRITE
#define CONFIG_ENV_OFFSET 0x400000
#define CONFIG_ENV_BLOCK_NUM 2
#elif defined CONFIG_MMC_BOOT
#define CONFIG_SYS_MMC_ENV_DEV 0
#define CONFIG_ENV_OFFSET 0x1000000
#else
#define CONFIG_ENV_IS_NOWHERE 1
#endif