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Subject[PATCH v1] list: Add a macro to test if entry is pointing to the head
Date
Add a macro to test if entry is pointing to the head of the list
which is useful in cases like:

list_for_each_entry(pos, &head, member) {
if (cond)
break;
}
if (list_entry_is_head(pos, &head, member))
return -ERRNO;

that allows to avoid additional variable to be added to track if loop
has not been stopped in the middle.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
include/linux/list.h | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/include/linux/list.h b/include/linux/list.h
index 796975c3c35c..49efaa8c3403 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -770,6 +770,17 @@ static inline void list_splice_tail_init(struct list_head *list,
#define list_safe_reset_next(pos, n, member) \
n = list_next_entry(pos, member)

+/**
+ * list_entry_is_head - test if the entry points to the head of the list
+ * @pos: the type * to cursor
+ * @head: the head for your list.
+ * @member: the name of the list_head within the struct.
+ *
+ * This macro can be used to check if the loop over the list wasn't stopped.
+ */
+#define list_entry_is_head(pos, head, member) \
+ (&pos->member == (head))
+
/*
* Double linked lists with a single pointer list head.
* Mostly useful for hash tables where the two pointer list head is
--
2.28.0
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