Hi3520DV300挂载根文件系统

  make ARCH=arm CROSS_COMPILE=arm-hisiv400-linux- menuconfig

  进入fs/nfs

  vi Kconfig

  搜索root

  config ROOT_NFS

  bool "Root file system on NFS"

  depends on NFS_FS=y && IP_PNP

  help

  If you want your system to mount its root file system via NFS,

  choose Y here.  This is common practice for managing systems

  without local permanent storage.  For details, read

  <file:Documentation/filesystems/nfs/nfsroot.txt>.

  Most people say N here.

  NFS_FS必然是已经打开了

  IP_PNP是什么?

  CONFIG_IP_PNP内核级IP自动配置，即启动时通过内核命令行参数配置，如ip=192.168.0.111...
  CONFIG_IP_PNP_XXX即支持XXX协议来配置IP，如及CONFIG_IP_PNP_DHCP=y则支持启动时支持ip=dhcp来配置ip

 在当前目录下

 grep -Irn "IP_PNP" .

 没有收获

 在kernel下 net下

 grep -Irn "IP_PNP" .

./ipv4/Makefile:36:obj-$(CONFIG_IP_PNP) += ipconfig.o

./ipv4/Kconfig:110:config IP_PNP

./ipv4/Kconfig:121:config IP_PNP_DHCP

./ipv4/Kconfig:123:     depends on IP_PNP

./ipv4/Kconfig:138:config IP_PNP_BOOTP

./ipv4/Kconfig:140:     depends on IP_PNP

./ipv4/Kconfig:153:config IP_PNP_RARP

./ipv4/Kconfig:155:     depends on IP_PNP

./ipv4/ipconfig.c:77:#if defined(CONFIG_IP_PNP_DHCP)

./ipv4/ipconfig.c:80:#if defined(CONFIG_IP_PNP_BOOTP) || defined(CONFIG_IP_PNP_DHCP)

./ipv4/ipconfig.c:83:#if defined(CONFIG_IP_PNP_RARP)

./ipv4/ipconfig.c:125:#ifdef CONFIG_IP_PNP_DHCP

./ipv4/ipconfig.c:1558:#ifdef CONFIG_IP_PNP_DHCP

./ipv4/ipconfig.c:1564:#ifdef CONFIG_IP_PNP_BOOTP

./ipv4/ipconfig.c:1570:#ifdef CONFIG_IP_PNP_RARP

打开Kconfig

config IP_PNP

111     bool "IP: kernel level autoconfiguration"

112     help

113       This enables automatic configuration of IP addresses of devices and

114       of the routing table during kernel boot, based on either information

115       supplied on the kernel command line or by BOOTP or RARP protocols.

116       You need to say Y only for diskless machines requiring network

117       access to boot (in which case you want to say Y to "Root file system

118       on NFS" as well), because all other machines configure the network

119       in their startup scripts.

120

121 config IP_PNP_DHCP

122     bool "IP: DHCP support"

123     depends on IP_PNP