1. cmd

命令行可以用setenv  printenv saveenv

uboot\u-boot-2020.04\cmd\nvedit.c

setenv -> do_env_set -> _do_env_set -> hsearch_r(env_htab)

printenv -> do_env_print -> env_print -> hsearch_r(env_htab)

saveenv -> do_env_save -> env_save

env_htab为env hash table，方便快速查找env变量。

example：

setenv ethaddr 64:00:F1:11:22:33 //eth0

setenv eth1addr 64:00:F1:44:55:66  //eth1

saveenv

2. env_load & env_save

uboot\u-boot-2020.04\env\mmc.c

U_BOOT_ENV_LOCATION(mmc) = {.location   = ENVL_MMC,ENV_NAME("MMC").load       = env_mmc_load,
#ifndef CONFIG_SPL_BUILD.save       = env_save_ptr(env_mmc_save),
#if defined(CONFIG_CMD_ERASEENV).erase      = env_mmc_erase,
#endif
#endif
};

env_load -> drv->load -> env_mmc_load -> mmc_get_env_addr & read_env & env_import( -> himport_r(&env_htab) ) & gd->env_addr

env_save -> drv->save -> env_mmc_save -> env_export & mmc_get_env_addr & write_env --> emmc

注：

env_import，导入env到hash table

env_export，从hash table导出到env

uboot启动时调用env_relocate -> env_load

emmc中有个env分区专门用来存储env变量

从mmc获得env分区信息：

mmc_get_env_addr -> mmc_offset

#ifdef USE_GPT_PARTITONret = part_get_info_by_name(blk_dev_desc, "env", &part_info);if (ret == -1) {printf("%s: get env partition info fail\n", __FUNCTION__);}#elseret = get_part_info(blk_dev_desc,"env", &part_info);if(ret == -1) {printf("%s: get env partition info fail\n", __FUNCTION__);}#endifelse {defvalue = part_info.start * part_info.blksz;}

3. env_set & env_get

代码中可以用 env_set & env_get

uboot\u-boot-2020.04\cmd\nvedit.c

env_get -> hsearch_r(env_htab) | env_get_f ->  env_get_char -> env_get_char_spec -> (gd->env_addr + index)

env_set -> _do_env_set -> hsearch_r(env_htab)

代码中修改环境变量，然后保存到emmc：

        env_load();    //非必须

        env_set("partions",buf);

        env_save();