Merge branch 'px4dev_new_param' of https://github.com/PX4/Firmware into px4dev_new_param

apps/systemlib/param/param.c

@@ -193,6 +193,15 @@ param_for_index(unsigned index)
 	return PARAM_INVALID;
 }
 
+int
+param_get_index(param_t param)
+{
+	if (handle_in_range(param))
+		return (unsigned)param;
+
+	return -1;
+}
+
 const char *
 param_name(param_t param)
 {

apps/systemlib/param/param.h

@@ -102,6 +102,14 @@ __EXPORT unsigned	param_count(void) __attribute__((const));
  */
 __EXPORT param_t	param_for_index(unsigned index) __attribute__((const));
 
+/**
+ * Look up the index of a parameter.
+ *
+ * @param param		The parameter to obtain the index for.
+ * @return		The index, or -1 if the parameter does not exist.
+ */
+__EXPORT int		param_get_index(param_t param) __attribute__((const));
+
 /**
  * Obtain the name of a parameter.
  *
@@ -156,7 +164,7 @@ __EXPORT int		param_set(param_t param, const void *val);
 __EXPORT int		param_export(int fd, bool only_unsaved);
 
 /**
- * Import parameters from a file, discarding any unrecognised parameters.
+ * Import parameters from a file, discarding any unrecognized parameters.
  *
  * @param fd		File descriptor to import from.  (Currently expected to be a file.)
  * @return		Zero on success, nonzero if an error occurred during import.
@@ -167,7 +175,9 @@ __EXPORT int		param_import(int fd);
 /**
  * Apply a function to each parameter.
  *
- * Note that the parameter set is not locked during the traversal.
+ * Note that the parameter set is not locked during the traversal. It also does
+ * not hold an internal state, so the callback function can block or sleep between
+ * parameter callbacks.
  *
  * @param func		The function to invoke for each parameter.
  * @param arg		Argument passed to the function.