bootcmd
在uboot的shell中使用printenv命令可以看到bootcmd的字符串：
=> printenv bootcmd
bootcmd=boot_android ${devtype} ${devnum};boot_fit;bootrkp;run distro_bootcmd;
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命令解析：
- boot_android: 查找并尝试启动安卓镜像。
- boot_fix: 查找并尝试启动fit格式镜像。
- bootrkp: 查找并尝试启动rk分区镜像。
- run distro_bootcmd: 这就是这篇文章的主角了，distro_bootcmd可以根据不同介质去启动kernel内核，比如kernel可以在sd卡，emmc上，都可以顺利启动。
以上提到的bootcmd可以在include/configs/rockchip-common.h中看到相关定义：
#if defined(CONFIG_AVB_VBMETA_PUBLIC_KEY_VALIDATE)
#define RKIMG_BOOTCOMMAND \
"boot_android ${devtype} ${devnum};"
#elif defined(CONFIG_FIT_SIGNATURE)
#define RKIMG_BOOTCOMMAND \
"boot_fit;"
#else
#define RKIMG_BOOTCOMMAND \
"boot_android ${devtype} ${devnum};" \
"boot_fit;" \
"bootrkp;" \
"run distro_bootcmd;"
#endif
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distro_bootcmd
现在来重点分析一下distro_bootcmd，首先使用打印出distro_bootcmd:
=> printenv distro_bootcmd
distro_bootcmd=for target in ${boot_targets}; do run bootcmd_${target}; done
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在uboot源码中找到对应实现，可以看到BOOTENV_SET_SCSI_NEED_INIT这个宏定义是空的，所以不必深究：
#define BOOTENV \
BOOTENV_BOOT_TARGETS
...
BOOT_TARGET_DEVICES(BOOTENV_DEV) \
\
"distro_bootcmd=" BOOTENV_SET_SCSI_NEED_INIT \
"for target in ${boot_targets}; do " \
"run bootcmd_${target}; " \
"done\0"
|
BOOTENV
在这个BOOTENV宏定义中，定义了distro_bootcmd的值，BOOTENV在include/configs/rk3568_common.h中被使用到：
CONFIG_EXTRA_ENV_SETTINGS \ ENV_MEM_LAYOUT_SETTINGS \
"partitions=" PARTS_RKIMG \
ROCKCHIP_DEVICE_SETTINGS \
RKIMG_DET_BOOTDEV \
BOOTENV
#endif
|
而CONFIG_EXTRA_ENV_SETTINGS又在include/env_default.h中被使用到：
#ifdef DEFAULT_ENV_INSTANCE_EMBEDDED
env_t environment __UBOOT_ENV_SECTION__ = {
ENV_CRC,
#ifdef CONFIG_SYS_REDUNDAND_ENVIRONMENT
1,
#endif
{
#elif defined(DEFAULT_ENV_INSTANCE_STATIC)
static char default_environment[] = {
#else
const uchar default_environment[] = {
#endif
#ifdef CONFIG_USE_BOOTARGS
"bootargs=" CONFIG_BOOTARGS "\0"
#endif
#ifdef CONFIG_BOOTCOMMAND
"bootcmd=" CONFIG_BOOTCOMMAND "\0"
#endif
#endif
...
#ifdef CONFIG_EXTRA_ENV_SETTINGS
CONFIG_EXTRA_ENV_SETTINGS
#endif
"\0"
#ifdef DEFAULT_ENV_INSTANCE_EMBEDDED
}
#endif
|
TODO 了解这个数组
回到distro_bootcmd：
#define BOOTENV \
BOOTENV_BOOT_TARGETS
...
BOOT_TARGET_DEVICES(BOOTENV_DEV) \
\
"distro_bootcmd=" BOOTENV_SET_SCSI_NEED_INIT \
"for target in ${boot_targets}; do " \
"run bootcmd_${target}; " \
"done\0"
|
这里其实就是一个循环，循环遍历 ${boot_targets}并执行bootcmd_${target},查看 ${boot_targets}相关定义：
#define BOOTENV_DEV_NAME(devtypeu, devtypel, instance) \
BOOTENV_DEV_NAME_##devtypeu(devtypeu, devtypel, instance)
#define BOOTENV_BOOT_TARGETS \
"boot_targets=" BOOT_TARGET_DEVICES(BOOTENV_DEV_NAME) "\0"
|
BOOTENV_BOOT_TARGETS生成boot_targets字符串
通过BOOTENV_BOOT_TARGETS宏定义生成了boot_targets字符串：
#define BOOTENV_DEV_NAME(devtypeu, devtypel, instance) \
BOOTENV_DEV_NAME_##devtypeu(devtypeu, devtypel, instance)
#define BOOTENV_BOOT_TARGETS \
"boot_targets=" BOOT_TARGET_DEVICES(BOOTENV_DEV_NAME) "\0"
|
[!NOTE]
BOOTENV_BOOT_TARGETS也是在BOOTENV中定义的
BOOTENV_BOOT_TARGETS调用了BOOT_TARGET_DEVICES宏定义，BOOT_TARGET_DEVICES就是在对应的芯片上或芯片系列的定义了，不同的芯片应有不同的实现：
#define BOOT_TARGET_DEVICES(func) \
BOOT_TARGET_MMC(func) \
BOOT_TARGET_MTD(func) \
BOOT_TARGET_RKNAND(func) \
BOOT_TARGET_USB(func) \
BOOT_TARGET_PXE(func) \
BOOT_TARGET_DHCP(func)
|
这里宏定义定义成了6个宏，这里只研究BOOT_TARGET_MMC，其他都是差不多的：
#if CONFIG_IS_ENABLED(CMD_MMC)
#define BOOT_TARGET_MMC(func) \
func(MMC, mmc, 1) \
func(MMC, mmc, 0)
#else
#define BOOT_TARGET_MMC(func)
#endif
|
逐级展开：
#define BOOTENV_DEV_NAME(devtypeu, devtypel, instance) \
BOOTENV_DEV_NAME_##devtypeu(devtypeu, devtypel, instance)
#define BOOTENV_BOOT_TARGETS \
"boot_targets=" BOOT_TARGET_DEVICES(BOOTENV_DEV_NAME) "\0"
->（这里就只展开mmc了，道理都一样）
"boot_targets=" BOOT_TARGET_MMC(BOOTENV_DEV_NAME) "\0"
->
"boot_targets=" BOOTENV_DEV_NAME(MMC, mmc, 1) \
BOOTENV_DEV_NAME(MMC, mmc, 0)"\0"
->
"boot_targets=" BOOTENV_DEV_NAME_MMC(MMC, mmc, 1) \
BOOTENV_DEV_NAME_MMC(MMC, mmc, 0)"\0"
|
BOOTENV_DEV_NAME_MMC宏定义:
#define BOOTENV_DEV_NAME_BLKDEV(devtypeu, devtypel, instance) \
#devtypel #instance " "
#define BOOTENV_DEV_NAME_MMC BOOTENV_DEV_NAME_BLKDEV
|
继续展开：
#define BOOTENV_DEV_NAME(devtypeu, devtypel, instance) \
BOOTENV_DEV_NAME_##devtypeu(devtypeu, devtypel, instance)
#define BOOTENV_BOOT_TARGETS \
"boot_targets=" BOOT_TARGET_DEVICES(BOOTENV_DEV_NAME) "\0"
->（这里就只展开mmc了，道理都一样）
"boot_targets=" BOOT_TARGET_MMC(BOOTENV_DEV_NAME) "\0"
->
"boot_targets=" BOOTENV_DEV_NAME(MMC, mmc, 1) \
BOOTENV_DEV_NAME(MMC, mmc, 0)"\0"
->
"boot_targets=" BOOTENV_DEV_NAME_MMC(MMC, mmc, 1) \
BOOTENV_DEV_NAME_MMC(MMC, mmc, 0)"\0"
->
"boot_targets=" BOOTENV_DEV_NAME_BLKDEV(MMC, mmc, 1) \
BOOTENV_DEV_NAME_BLKDEV(MMC, mmc, 0)"\0"
->
"boot_targets=" mmc1 mmc0 "\0"
|
最后boot_targets就变成了下面这样，同时在uboot的shell中验证也是这样：
=> printenv boot_targets
boot_targets=mmc1 mmc0 mtd2 mtd1 mtd0 usb0 pxe dhcp
|
boot_targets分析完了，但这只是我们distro_bootcmd循环的变量而已，还有一个run bootcmd_${target};没有分析，通过boot_targets能知道，这运行的大概就是bootcmd_mmc0, bootcmd_mmc1这样的东西。
生成distro_cmd运行命令
在BOOTENV中有一个宏调用是BOOT_TARGET_DEVICES(BOOTENV_DEV)（上文BOOTENV代码中贴了），现在回顾一下BOOT_TARGET_DEVICES:
#define BOOT_TARGET_DEVICES(func) \
BOOT_TARGET_MMC(func) \
BOOT_TARGET_MTD(func) \
BOOT_TARGET_RKNAND(func) \
BOOT_TARGET_USB(func) \
BOOT_TARGET_PXE(func) \
BOOT_TARGET_DHCP(func)
|
BOOTENV_DEV定义如下：
#define BOOTENV_DEV_BLKDEV(devtypeu, devtypel, instance) \
"bootcmd_" #devtypel #instance "=" \
"setenv devnum " #instance "; " \
"run " #devtypel "_boot\0"
|
逐级展开（只讨论mmc）:
BOOT_TARGET_DEVICES(BOOTENV_DEV)
->（这里就只展开mmc了，道理都一样）
BOOT_TARGET_MMC(BOOTENV_DEV) \
->
BOOTENV_DEV(MMC, mmc, 1) \
BOOTENV_DEV(MMC, mmc, 0)"\0"
->
"bootcmd_mmc1=setenv devnum 1;run mmc1_boot\0" \
"bootcmd_mmc0=setenv devnum 0;run mmc0_boot\0" \
|
Ref
https://blog.csdn.net/Andyshrk/article/details/89136721
https://juejin.cn/post/7202851843488088125
