From: Vignesh Raghavendra <vigneshr@ti.com>
Date: Tue, 1 Oct 2019 11:56:29 +0000 (+0530)
Subject: list: import list_first_entry_or_null()
X-Git-Tag: v2020.01-rc2~7^2~9
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=c37f594280aa3fc9d534420581f7db47ac843297;p=oweals%2Fu-boot.git

list: import list_first_entry_or_null()

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>
---

diff --git a/include/linux/list.h b/include/linux/list.h
index 5b8d1df5df..f62afa092c 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.