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