1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_CONTAINER_OF_H
3 #define _LINUX_CONTAINER_OF_H
4
5 #include <linux/build_bug.h>
6 #include <linux/stddef.h>
7
8 #define typeof_member(T, m) typeof(((T*)0)->m)
9
10 /**
11 * container_of - cast a member of a structure out to the containing structure
12 * @ptr: the pointer to the member.
13 * @type: the type of the container struct this is embedded in.
14 * @member: the name of the member within the struct.
15 *
16 * WARNING: any const qualifier of @ptr is lost.
17 */
18 #define container_of(ptr, type, member) ({ \
19 void *__mptr = (void *)(ptr); \
20 static_assert(__same_type(*(ptr), ((type *)0)->member) || \
21 __same_type(*(ptr), void), \
22 "pointer type mismatch in container_of()"); \
23 ((type *)(__mptr - offsetof(type, member))); })
24
25 /**
26 * container_of_const - cast a member of a structure out to the containing
27 * structure and preserve the const-ness of the pointer
28 * @ptr: the pointer to the member
29 * @type: the type of the container struct this is embedded in.
30 * @member: the name of the member within the struct.
31 */
32 #define container_of_const(ptr, type, member) \
33 _Generic(ptr, \
34 const typeof(*(ptr)) *: ((const type *)container_of(ptr, type, member)),\
35 default: ((type *)container_of(ptr, type, member)) \
36 )
37
38 #endif /* _LINUX_CONTAINER_OF_H */
39
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