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[1/6] list: introduce list_last_entry_or_null()

Message ID 5285A393.8000808@oracle.com
State Not Applicable
Headers show

Commit Message

jeff.liu Nov. 15, 2013, 4:31 a.m. UTC 
From: Jie Liu <jeff.liu@oracle.com>

Introduce a trivial helper list_last_entry_or_null() to fetch the
last entry from a list, return NULL if the list is empty.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
---
 include/linux/list.h | 11 +++++++++++
 1 file changed, 11 insertions(+)
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Patch

diff --git a/include/linux/list.h b/include/linux/list.h
index ef95941..3337249 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -384,6 +384,17 @@  static inline void list_splice_tail_init(struct list_head *list,
 	(!list_empty(ptr) ? list_first_entry(ptr, type, member) : NULL)
 
 /**
+ * list_last_entry_or_null - get the last element from a list
+ * @ptr:	the list head to take the element from.
+ * @type:	the type of the struct this is embedded in.
+ * @member:	the name of the list_struct within the struct.
+ *
+ * Note that if the list is empty, it returns NULL.
+ */
+#define list_last_entry_or_null(ptr, type, member) \
+	(!list_empty(ptr) ? list_last_entry(ptr, type, member) : NULL)
+
+/**
  * list_next_entry - get the next element in list
  * @pos:	the type * to cursor
  * @member:	the name of the list_struct within the struct.