Add macros to get the next or previous entries and wraparound if
needed. For example, calling list_next_entry_circular() on the last
element should return the first element in the list.
Signed-off-by: Ricardo Martinez <[email protected]>
---
include/linux/list.h | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/include/linux/list.h b/include/linux/list.h
index dd6c2041d09c..c147eeb2d39d 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -563,6 +563,19 @@ static inline void list_splice_tail_init(struct list_head *list,
#define list_next_entry(pos, member) \
list_entry((pos)->member.next, typeof(*(pos)), member)
+/**
+ * list_next_entry_circular - get the next element in list
+ * @pos: the type * to cursor.
+ * @head: the list head to take the element from.
+ * @member: the name of the list_head within the struct.
+ *
+ * Wraparound if pos is the last element (return the first element).
+ * Note, that list is expected to be not empty.
+ */
+#define list_next_entry_circular(pos, head, member) \
+ (list_is_last(&(pos)->member, head) ? \
+ list_first_entry(head, typeof(*(pos)), member) : list_next_entry(pos, member))
+
/**
* list_prev_entry - get the prev element in list
* @pos: the type * to cursor
@@ -571,6 +584,19 @@ static inline void list_splice_tail_init(struct list_head *list,
#define list_prev_entry(pos, member) \
list_entry((pos)->member.prev, typeof(*(pos)), member)
+/**
+ * list_prev_entry_circular - get the prev element in list
+ * @pos: the type * to cursor.
+ * @head: the list head to take the element from.
+ * @member: the name of the list_head within the struct.
+ *
+ * Wraparound if pos is the first element (return the last element).
+ * Note, that list is expected to be not empty.
+ */
+#define list_prev_entry_circular(pos, head, member) \
+ (list_is_first(&(pos)->member, head) ? \
+ list_last_entry(head, typeof(*(pos)), member) : list_prev_entry(pos, member))
+
/**
* list_for_each - iterate over a list
* @pos: the &struct list_head to use as a loop cursor.
--
2.17.1
On Thu, Jan 13, 2022 at 06:06:15PM -0700, Ricardo Martinez wrote:
> Add macros to get the next or previous entries and wraparound if
> needed. For example, calling list_next_entry_circular() on the last
> element should return the first element in the list.
FWIW,
Reviewed-by: Andy Shevchenko <[email protected]>
> Signed-off-by: Ricardo Martinez <[email protected]>
> ---
> include/linux/list.h | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/include/linux/list.h b/include/linux/list.h
> index dd6c2041d09c..c147eeb2d39d 100644
> --- a/include/linux/list.h
> +++ b/include/linux/list.h
> @@ -563,6 +563,19 @@ static inline void list_splice_tail_init(struct list_head *list,
> #define list_next_entry(pos, member) \
> list_entry((pos)->member.next, typeof(*(pos)), member)
>
> +/**
> + * list_next_entry_circular - get the next element in list
> + * @pos: the type * to cursor.
> + * @head: the list head to take the element from.
> + * @member: the name of the list_head within the struct.
> + *
> + * Wraparound if pos is the last element (return the first element).
> + * Note, that list is expected to be not empty.
> + */
> +#define list_next_entry_circular(pos, head, member) \
> + (list_is_last(&(pos)->member, head) ? \
> + list_first_entry(head, typeof(*(pos)), member) : list_next_entry(pos, member))
> +
> /**
> * list_prev_entry - get the prev element in list
> * @pos: the type * to cursor
> @@ -571,6 +584,19 @@ static inline void list_splice_tail_init(struct list_head *list,
> #define list_prev_entry(pos, member) \
> list_entry((pos)->member.prev, typeof(*(pos)), member)
>
> +/**
> + * list_prev_entry_circular - get the prev element in list
> + * @pos: the type * to cursor.
> + * @head: the list head to take the element from.
> + * @member: the name of the list_head within the struct.
> + *
> + * Wraparound if pos is the first element (return the last element).
> + * Note, that list is expected to be not empty.
> + */
> +#define list_prev_entry_circular(pos, head, member) \
> + (list_is_first(&(pos)->member, head) ? \
> + list_last_entry(head, typeof(*(pos)), member) : list_prev_entry(pos, member))
> +
> /**
> * list_for_each - iterate over a list
> * @pos: the &struct list_head to use as a loop cursor.
> --
> 2.17.1
>
--
With Best Regards,
Andy Shevchenko