diff mbox series

[U-Boot,1/8] list: import list_first_entry_or_null()

Message ID 20191001115636.21052-2-vigneshr@ti.com
State Accepted
Commit c37f594280aa3fc9d534420581f7db47ac843297
Delegated to: Lukasz Majewski
Headers show
Series usb: Add support for Cadence USB controller driver | expand

Commit Message

Raghavendra, Vignesh Oct. 1, 2019, 11:56 a.m. UTC 
Import list_first_entry_or_null() macro from Linux that would be used
by Cadence USB driver

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
---
 include/linux/list.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
diff mbox series

Patch

diff --git a/include/linux/list.h b/include/linux/list.h
index 5b8d1df5dfee..f62afa092c63 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -348,6 +348,20 @@  static inline void list_splice_tail_init(struct list_head *list,
 #define list_last_entry(ptr, type, member) \
 	list_entry((ptr)->prev, type, member)
 
+/**
+ * list_first_entry_or_null - get the first 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_head within the struct.
+ *
+ * Note that if the list is empty, it returns NULL.
+ */
+#define list_first_entry_or_null(ptr, type, member) ({ \
+	struct list_head *head__ = (ptr); \
+	struct list_head *pos__ = READ_ONCE(head__->next); \
+	pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
+})
+
 /**
  * list_for_each	-	iterate over a list
  * @pos:	the &struct list_head to use as a loop cursor.