linux-kernel - [RFC v3 05/17] tools lib: Add list_last_entry_or

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Message-ID: <20220709015033.38326-6-yangjihong1@huawei.com>
Date:   Sat, 9 Jul 2022 09:50:21 +0800
From:   Yang Jihong <yangjihong1@...wei.com>
To:     <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
        <mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
        <jolsa@...nel.org>, <namhyung@...nel.org>, <pc@...ibm.com>,
        <linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>
CC:     <yangjihong1@...wei.com>
Subject: [RFC v3 05/17] tools lib: Add list_last_entry_or_null

Add list_last_entry_or_null to get the last element from a list,
returns NULL if the list is empty.

Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
---
 tools/include/linux/list.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tools/include/linux/list.h b/tools/include/linux/list.h
index b2fc48d5478c..a4dfb6a7cc6a 100644
--- a/tools/include/linux/list.h
+++ b/tools/include/linux/list.h
@@ -384,6 +384,17 @@ static inline void list_splice_tail_init(struct list_head *list,
 #define list_first_entry_or_null(ptr, type, member) \
 	(!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_head 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
-- 
2.30.GIT