netdev - [PATCH net-next v5 01/13] list: Add list_next_entry_circular() and list_prev_entry

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Date:   Wed, 23 Feb 2022 15:33:14 -0700
From:   Ricardo Martinez <ricardo.martinez@...ux.intel.com>
To:     netdev@...r.kernel.org, linux-wireless@...r.kernel.org
Cc:     kuba@...nel.org, davem@...emloft.net, johannes@...solutions.net,
        ryazanov.s.a@...il.com, loic.poulain@...aro.org,
        m.chetan.kumar@...el.com, chandrashekar.devegowda@...el.com,
        linuxwwan@...el.com, chiranjeevi.rapolu@...ux.intel.com,
        haijun.liu@...iatek.com, amir.hanania@...el.com,
        andriy.shevchenko@...ux.intel.com, dinesh.sharma@...el.com,
        eliot.lee@...el.com, ilpo.johannes.jarvinen@...el.com,
        moises.veleta@...el.com, pierre-louis.bossart@...el.com,
        muralidharan.sethuraman@...el.com, Soumya.Prakash.Mishra@...el.com,
        sreehari.kancharla@...el.com, madhusmita.sahu@...el.com,
        Ricardo Martinez <ricardo.martinez@...ux.intel.com>
Subject: [PATCH net-next v5 01/13] list: Add list_next_entry_circular() and list_prev_entry_circular()

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 <ricardo.martinez@...ux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 include/linux/list.h | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

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.
-- 
2.17.1