[net-next,v7,01/14] list: Add list_next_entry_circular() and list_prev_entry_circular()

Commit Message

Ricardo Martinez May 6, 2022, 1:16 a.m. UTC

Add macros to get the next or previous entries and wraparound if
needed. For example, calling list_next_entry_circular() on the last
element should return the first element in the list.

Signed-off-by: Ricardo Martinez <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
---
 include/linux/list.h | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

Patch

diff --git a/include/linux/list.h b/include/linux/list.h
index dd6c2041d09c..c147eeb2d39d 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -563,6 +563,19 @@  static inline void list_splice_tail_init(struct list_head *list,
 #define list_next_entry(pos, member) \
 	list_entry((pos)->member.next, typeof(*(pos)), member)
 
+/**
+ * list_next_entry_circular - get the next element in list
+ * @pos:	the type * to cursor.
+ * @head:	the list head to take the element from.
+ * @member:	the name of the list_head within the struct.
+ *
+ * Wraparound if pos is the last element (return the first element).
+ * Note, that list is expected to be not empty.
+ */
+#define list_next_entry_circular(pos, head, member) \
+	(list_is_last(&(pos)->member, head) ? \
+	list_first_entry(head, typeof(*(pos)), member) : list_next_entry(pos, member))
+
 /**
  * list_prev_entry - get the prev element in list
  * @pos:	the type * to cursor
@@ -571,6 +584,19 @@  static inline void list_splice_tail_init(struct list_head *list,
 #define list_prev_entry(pos, member) \
 	list_entry((pos)->member.prev, typeof(*(pos)), member)
 
+/**
+ * list_prev_entry_circular - get the prev element in list
+ * @pos:	the type * to cursor.
+ * @head:	the list head to take the element from.
+ * @member:	the name of the list_head within the struct.
+ *
+ * Wraparound if pos is the first element (return the last element).
+ * Note, that list is expected to be not empty.
+ */
+#define list_prev_entry_circular(pos, head, member) \
+	(list_is_first(&(pos)->member, head) ? \
+	list_last_entry(head, typeof(*(pos)), member) : list_prev_entry(pos, member))
+
 /**
  * list_for_each	-	iterate over a list
  * @pos:	the &struct list_head to use as a loop cursor.