[U-Boot,RFC,3/4] env: implement selective "env default"

diff --git a/README b/README
index a43da97..4b28854 100644
--- a/README
+++ b/README
@@ -705,6 +705,8 @@  The following options need to be configured:
 		CONFIG_CMD_CONSOLE	  coninfo
 		CONFIG_CMD_CRC32	* crc32
 		CONFIG_CMD_DATE		* support for RTC, date/time...
+		CONFIG_CMD_DEFAULTENV_VARS
+					* Reset individual variables to default
 		CONFIG_CMD_DHCP		* DHCP support
 		CONFIG_CMD_DIAG		* Diagnostics
 		CONFIG_CMD_DS4510	* ds4510 I2C gpio commands
diff --git a/common/cmd_nvedit.c b/common/cmd_nvedit.c
index 506a251..8636004 100644
--- a/common/cmd_nvedit.c
+++ b/common/cmd_nvedit.c
@@ -615,13 +615,36 @@  int envmatch(uchar *s1, int i2)
 	return -1;
 }
 
-static int do_env_default(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+static int do_env_default(cmd_tbl_t *cmdtp, int __flag, int argc, char * const argv[])
 {
-	if ((argc != 2) || (strcmp(argv[1], "-f") != 0))
-		return cmd_usage(cmdtp);
-
-	set_default_env("## Resetting to default environment\n");
-	return 0;
+	int all = 0, flag = 0;
+	debug("Initial value for argc=%d\n", argc);
+	while (--argc > 0 && **++argv == '-') {
+		char *arg = *argv;
+		while (*++arg) {
+			switch (*arg) {
+			case 'a':		/* default all */
+				all = 1;
+				break;
+			case 'f':		/* force */
+				flag |= H_FORCE;
+				break;
+			default:
+				return cmd_usage(cmdtp);
+			}
+		}
+	}
+	debug("Final value for argc=%d\n", argc);
+	if (all && (argc == 0)) {
+		/* Reset the whole environment */
+		set_default_env("## Resetting to default environment\n");
+		return 0;
+	} else if (!all && (argc > 0)) {
+		/* Reset individual variables */
+		env_default_vars(argc, argv);
+		return 0;
+	}
+	return cmd_usage(cmdtp);
 }
 
 static int do_env_delete(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
@@ -947,6 +970,9 @@  U_BOOT_CMD(
 	"ask name [message] [size] - ask for environment variable\nenv "
 #endif
 	"default -f - reset default environment\n"
+#if defined(CONFIG_CMD_DEFAULTENV_VARS)
+	"env default var [...] - reset variable(s) to their default value\n"
+#endif
 #if defined(CONFIG_CMD_EDITENV)
 	"env edit name - edit environment variable\n"
 #endif
diff --git a/common/env_common.c b/common/env_common.c
index 7e1d824..c2769a8 100644
--- a/common/env_common.c
+++ b/common/env_common.c
@@ -207,6 +207,19 @@  void set_default_env(const char *s)
 	gd->flags |= GD_FLG_ENV_READY;
 }
 
+#ifdef CONFIG_CMD_DEFAULTENV_VARS
+
+/* [re]set individual variables to their value in the default environment */
+int env_default_vars(int nvars, char * const vars[])
+{
+	/* Special use-case: import from default environment
+	   (and use \0 as a separator) */
+	return himport_ex(&env_htab, (const char *)default_environment, sizeof(default_environment), '\0', H_NOCLEAR,
+			 nvars, vars, env_check_apply);
+}
+
+#endif /* CONFIG_CMD_DEFAULTENV_VARS */
+
 /*
  * Check if CRC is valid and (if yes) import the environment.
  * Note that "buf" may or may not be aligned.
diff --git a/include/config_cmd_all.h b/include/config_cmd_all.h
index 9716f9c..e728eae 100644
--- a/include/config_cmd_all.h
+++ b/include/config_cmd_all.h
@@ -25,6 +25,7 @@ 
 #define CONFIG_CMD_CDP		/* Cisco Discovery Protocol	*/
 #define CONFIG_CMD_CONSOLE	/* coninfo			*/
 #define CONFIG_CMD_DATE		/* support for RTC, date/time...*/
+#define CONFIG_CMD_DEFAULTENV_VARS /* default individ variables */
 #define CONFIG_CMD_DHCP		/* DHCP Support			*/
 #define CONFIG_CMD_DIAG		/* Diagnostics			*/
 #define CONFIG_CMD_DISPLAY	/* Display support		*/
diff --git a/include/environment.h b/include/environment.h
index 02c3488..7555c3b 100644
--- a/include/environment.h
+++ b/include/environment.h
@@ -171,6 +171,11 @@  void env_crc_update (void);
 /* [re]set to the default environment */
 void set_default_env(const char *s);
 
+#ifdef CONFIG_CMD_DEFAULTENV_VARS
+/* [re]set individual variables to their value in the default environment */
+int env_default_vars(int nvars, char * const vars[]);
+#endif
+
 /* Import from binary representation into hash table */
 int env_import(const char *buf, int check);