Added clear_setting()

src/core/settings.c

 	return setting;
 }
 
-/** Show value of setting
+/**
+ * Show value of setting
  *
  * @v context		Configuration context
  * @v name		Configuration setting name
 	return setting->type->show ( context, setting, buf, len );
 }
 
-/** Set value of setting
+/**
+ * Set value of setting
  *
  * @v context		Configuration context
  * @v name		Configuration setting name
 	return setting->type->set ( context, setting, value );
 }
 
+/**
+ * Clear setting
+ *
+ * @v context		Configuration context
+ * @v name		Configuration setting name
+ * @ret rc		Return status code
+ */
+int clear_setting ( struct config_context *context, const char *name ) {
+	struct config_setting *setting;
+	struct config_setting tmp_setting;
+
+	setting = find_or_build_config_setting ( name, &tmp_setting );
+	if ( ! setting )
+		return -ENOENT;
+
+	/* All types of settings get cleared the same way */
+	delete_dhcp_option ( context->options, setting->tag );
+
+	return 0;
+}
+
 /**
  * Show value of string setting
  *

src/include/gpxe/settings.h

 			  char *buf, size_t len );
 extern int set_setting ( struct config_context *context, const char *name,
 			 const char *value );
+extern int clear_setting ( struct config_context *context, const char *name );
 
 #endif /* _GPXE_SETTINGS_H */