uboot CONFIG_SYS_HUSH_PARSER 选项

u-boot中配置选项众多，有些配置选择提供了很好的功能，CONFIG_SYS_HUSH_PARSER 选项就提供了比较实用的功能，

看看一个例子：

在CONFIG_SYS_HUSH_PARSER 选项没有打开之前的运行结果:

环境变量配置如下:

 bootcmd:

"setenv bootargs root=/dev/nfs rw nfsroot=$serverip:$rootpath" \

      "ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname:$netdev:off" \

       "console=$consoledev,$baudrate$othbootargs;" \

       "tftp $loadaddr $bootfile;"\

       "tftp $fdtaddr $fdtfile;"\

       "bootm $loadaddr -$fdtaddr"

...

bootfile=uImage

loadaddr=0x01000000

       fdtaddr=0x00c00000

       fdtfile=EVM440.dtb

...

EVM440:/#boot

Setting the MAC address 0:11:3c:6e:f3:5f

TFTP from server 10.159.201.10; our IP address is10.141.179.215

Filename '$bootfile'.

Load address: 0x0

Loading: ## Warning: gatewayip needed but not set

T

TFTP error: 'File not found' (1)

Not retrying...

Setting the MAC address 0:11:3c:6e:f3:5f

TFTP from server 10.159.201.10; our IP address is10.141.179.215

Filename '$fdtfile'.

Load address: 0x0

Loading: ## Warning: gatewayip needed but not set

TFTP error: 'File not found' (1)

Not retrying...

配置CONFIG_SYS_HUSH_PARSER选项后，结果是:

EVM440:/#boot

Setting the MAC address 0:11:3c:6e:f3:5f

TFTP from server 10.159.201.10; our IP address is10.141.179.215

Filename 'uImage'.

Load address: 0x1000000

Loading: ## Warning: gatewayip needed but not set

T

TFTP error: 'File not found' (1)

Not retrying...

Setting the MAC address 0:11:3c:6e:f3:5f

TFTP from server 10.159.201.10; our IP address is10.141.179.215

Filename 'EVM440.dtb'.

Load address: 0xc00000

Loading: ## Warning: gatewayip needed but not set

TFTP error: 'File not found' (1)

Not retrying...

也就是说没有配置CONFIG_SYS_HUSH_PARSER选项则不会解析，直接使用$loadaddr，而CONFIG_SYS_HUSH_PARSER选项配置后，$loadaddr被解析成0x1000000，CONFIG_SYS_HUSH_PARSER选项为u-boot环境变量配置提供了更灵活的机制.