1.“cannot create /proc/sys/kernel/hotplug: nonexistent directory” 错误。

CONFIG_PROC_FS=y
CONFIG_PROC_SYSCTL=y
CONFIG_HOTPLUG=y
CONFIG_NET=y
如果CONFIG_HOTPLUG和CONFIG_NET不选或没全选上的话，/proc/sys/kernel下将不会创建hotplug文件.(参见kernel/sysctl.c)
其中首页的[ ] Networking support ---> 配置CONFIG_NET=y
也可以编辑.config文件：
cat .config | grep CONFIG_HOTPLUG
CONFIG_HOTPLUG=y
cat .config | grep CONFIG_NET
CONFIG_NET=y

2.内核启动的时候出现
Partially written block 48 detected
Partially written block 48 detected
Partially written block 48 detected
Partially written block 48 detected
Partially written block 48 detected
Partially written block 48 detected
Partially written block 48 detected
Partially written block 48 detected
Partially written block 48 detected

这种提示信息是正常的，Partially written block 在正常使用时，文件系统的垃圾收集程序将会处理。
可以屏蔽这个信息，或者仅在YAFFS_TRACE_SCAN的时候显示这个信息，修改yaffs_guts.c文件的6668行，将
T(YAFFS_TRACE_ALWAYS,
(TSTR("Partially written block %d detected" TENDSTR),
blk));
改为：
T(YAFFS_TRACE_SCAN,
(TSTR("Partially written block %d detected" TENDSTR),
blk));