[settings] Use a generic setting's own type as its default type

When fetching a named setting using a name that does not explicitly
specify a type, default to using the type stored when the setting was
created, rather than always defaulting to "string".  This allows the
behaviour of user-defined settings to match the behaviour of
predefined settings (which have a sensible default type).

For example:

  set server:ipv4 192.168.0.1
  echo ${server}

will now print "192.168.0.1", rather than trying to print out the raw
IPv4 address bytes as a string.

The downside of this change is that existing tricks for printing
special characters within scripts may require (backwards-compatible)
modification.  For example, the "clear screen" sequence:

  set esc:hex 1b
  set cls ${esc}[2J
  echo ${cls}

will now have to become

  set esc:hex 1b
  set cls ${esc:string}[2J  # Must now explicitly specify ":string"
  echo ${cls}

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/settings.c

 	if ( len > generic->data_len )
 		len = generic->data_len;
 	memcpy ( data, generic_setting_data ( generic ), len );
+
+	/* Set setting type, if not yet specified */
+	if ( ! setting->type )
+		setting->type = generic->setting.type;
+
 	return generic->data_len;
 }
 
 	if ( setting_applies ( settings, setting ) &&
 	     ( ( ret = settings->op->fetch ( settings, setting,
 					     data, len ) ) >= 0 ) ) {
+		/* Record origin, if applicable */
 		if ( origin )
 			*origin = settings;
+		/* Default to string setting type, if not yet specified */
+		if ( ! setting->type )
+			setting->type = &setting_type_string;
 		return ret;
 	}
 
  * @v get_child		Function to find or create child settings block
  * @v settings		Settings block to fill in
  * @v setting		Setting to fill in
+ * @v default_type	Default type to use, if none specified
  * @v tmp_name		Buffer for copy of setting name
  * @ret rc		Return status code
  *
 		     struct settings * ( * get_child ) ( struct settings *,
 							 const char * ),
 		     struct settings **settings, struct setting *setting,
+		     struct setting_type *default_type,
 		     char *tmp_name ) {
 	char *settings_name;
 	char *setting_name;
 	*settings = &settings_root;
 	memset ( setting, 0, sizeof ( *setting ) );
 	setting->name = "";
-	setting->type = &setting_type_string;
+	setting->type = default_type;
 
 	/* Split name into "[settings_name/]setting_name[:type_name]" */
 	strcpy ( tmp_name, name );
 			  setting->name, setting->type->name );
 }
 
+/**
+ * Store value of named setting
+ *
+ * @v name		Name of setting
+ * @v default_type	Default type to use, if none specified
+ * @v data		Setting data, or NULL to clear setting
+ * @v len		Length of setting data
+ * @ret rc		Return status code
+ */
+int store_named_setting ( const char *name, struct setting_type *default_type,
+			  const void *data, size_t len ) {
+	struct settings *settings;
+	struct setting setting;
+	char tmp_name[ strlen ( name ) + 1 ];
+	int rc;
+
+	/* Parse setting name */
+	if ( ( rc = parse_setting_name ( name, autovivify_child_settings,
+					 &settings, &setting, default_type,
+					 tmp_name ) ) != 0 )
+		return rc;
+
+	/* Store setting */
+	if ( ( rc = store_setting ( settings, &setting, data, len ) ) != 0 )
+		return rc;
+
+	return 0;
+}
+
 /**
  * Parse and store value of named setting
  *
  * @v name		Name of setting
+ * @v default_type	Default type to use, if none specified
  * @v value		Formatted setting data, or NULL
  * @ret rc		Return status code
  */
-int storef_named_setting ( const char *name, const char *value ) {
+int storef_named_setting ( const char *name, struct setting_type *default_type,
+			   const char *value ) {
 	struct settings *settings;
 	struct setting setting;
 	char tmp_name[ strlen ( name ) + 1 ];
 
 	/* Parse setting name */
 	if ( ( rc = parse_setting_name ( name, autovivify_child_settings,
-					 &settings, &setting, tmp_name )) != 0)
+					 &settings, &setting, default_type,
+					 tmp_name ) ) != 0 )
 		return rc;
 
 	/* Store setting */
 	int rc;
 
 	/* Parse setting name */
-	if ( ( rc = parse_setting_name ( name, find_child_settings,
-					 &settings, &setting, tmp_name )) != 0)
+	if ( ( rc = parse_setting_name ( name, find_child_settings, &settings,
+					 &setting, NULL, tmp_name ) ) != 0 )
 		return rc;
 
 	/* Fetch setting */

src/hci/commands/menu_cmd.c

 		goto err_show_menu;
 
 	/* Store setting */
-	if ( ( rc = storef_named_setting ( setting, item->label ) ) != 0 ) {
+	if ( ( rc = storef_named_setting ( setting, &setting_type_string,
+					   item->label ) ) != 0 ) {
 		printf ( "Could not store \"%s\": %s\n",
 			 setting, strerror ( rc ) );
 		goto err_store;

src/hci/commands/nvo_cmd.c

 		goto err_get_value;
 
 	/* Determine total length of command line */
-	if ( ( rc = storef_named_setting ( name, value ) ) != 0 ) {
+	if ( ( rc = storef_named_setting ( name, &setting_type_string,
+					   value ) ) != 0 ) {
 		printf ( "Could not %s \"%s\": %s\n",
 			 argv[0], name, strerror ( rc ) );
 		goto err_store;

src/include/ipxe/settings.h

 extern int storef_setting ( struct settings *settings,
 			    struct setting *setting,
 			    const char *value );
-extern int storef_named_setting ( const char *name, const char *value );
+extern int store_named_setting ( const char *name,
+				 struct setting_type *default_type,
+				 const void *data, size_t len );
+extern int storef_named_setting ( const char *name,
+				  struct setting_type *default_type,
+				  const char *value );
 extern int fetchf_named_setting ( const char *name, char *name_buf,
 				  size_t name_len, char *value_buf,
 				  size_t value_len );
  * @ret rc		Return status code
  */
 static inline int delete_named_setting ( const char *name ) {
-	return storef_named_setting ( name, NULL );
+	return store_named_setting ( name, NULL, NULL, 0 );
 }
 
 /**