Missing LIST_PREV() ?

[Hans Petter Selasky]

Hi,

Why should LISTs only be forward traversable? The following piece of code make 
lists backward traversable:

/sys/sys/queue.h:

+#define LIST_PREV(head,elm,field) \
+  (((elm) == LIST_FIRST(head)) ? ((__typeof(elm))0) : \
+   ((__typeof(elm))(((uint8_t *)((elm)->field.le_prev)) - \
+                   ((uint8_t *)&LIST_NEXT((__typeof(elm))0,field)))))


Any comments?

--HPS