/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_CONTAINER_OF_H
#define _LINUX_CONTAINER_OF_H

#include <linux/build_bug.h>
#include <linux/stddef.h>

#define typeof_member(T, m)     typeof(((T*)0)->m)

/**
 * container_of - cast a member of a structure out to the containing structure
 * @ptr:        the pointer to the member.
 * @type:       the type of the container struct this is embedded in.
 * @member:     the name of the member within the struct.
 *
 * WARNING: any const qualifier of @ptr is lost.
 * Do not use container_of() in new code.
 */
#define container_of(ptr, type, member) ({                              \
        void *__mptr = (void *)(ptr);                                   \
        static_assert(__same_type(*(ptr), ((type *)0)->member) ||       \
                      __same_type(*(ptr), void),                        \
                      "pointer type mismatch in container_of()");       \
        ((type *)(__mptr - offsetof(type, member))); })

/**
 * container_of_const - cast a member of a structure out to the containing
 *                      structure and preserve the const-ness of the pointer
 * @ptr:                the pointer to the member
 * @type:               the type of the container struct this is embedded in.
 * @member:             the name of the member within the struct.
 *
 * Always prefer container_of_const() instead of container_of() in new code.
 */
#define container_of_const(ptr, type, member)                           \
        _Generic(ptr,                                                   \
                const typeof(*(ptr)) *: ((const type *)container_of(ptr, type, member)),\
                default: ((type *)container_of(ptr, type, member))      \
        )

#endif  /* _LINUX_CONTAINER_OF_H */