ELiTo/NFS: take default nfsroot from environment

Signed-off-by: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>

fs/nfs/Kconfig

@@ -168,6 +168,17 @@ config ROOT_NFS
 
 	  Most people say N here.
 
+config DEFAULT_ROOT_NFS_FROM_ENV
+        string
+        depends on ROOT_NFS
+	option env=DEFAULT_NFSROOT
+
+config DEFAULT_ROOT_NFS
+        string
+        depends on ROOT_NFS
+        default DEFAULT_ROOT_NFS_FROM_ENV if DEFAULT_ROOT_NFS_FROM_ENV != ''
+	default ''
+
 config NFS_FSCACHE
 	bool "Provide NFS client caching support"
 	depends on NFS_FS=m && FSCACHE || NFS_FS=y && FSCACHE=y

fs/nfs/nfsroot.c

@@ -132,6 +132,9 @@ static int __init nfs_root_setup(char *line)
 {
 	ROOT_DEV = Root_NFS;
 
+	if (strcmp(line, "default") == 0)
+		line = CONFIG_DEFAULT_ROOT_NFS;
+
 	if (line[0] == '/' || line[0] == ',' || (line[0] >= '0' && line[0] <= '9')) {
 		strlcpy(nfs_root_parms, line, sizeof(nfs_root_parms));
 	} else {