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list: import list_first_entry_or_null()

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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>
This commit is contained in:
Vignesh Raghavendra 2019-10-01 17:26:29 +05:30 committed by Marek Vasut
parent 0f282c1876
commit c37f594280
1 changed files with 14 additions and 0 deletions
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14
include/linux/list.h
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@ -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.