include/linux/container_of.h

   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/err.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  */
  17 #define container_of(ptr, type, member) ({                              \
  18         void *__mptr = (void *)(ptr);                                   \
  19         static_assert(__same_type(*(ptr), ((type *)0)->member) ||       \
  20                       __same_type(*(ptr), void),                        \
  21                       "pointer type mismatch in container_of()");       \
  22         ((type *)(__mptr - offsetof(type, member))); })
  23
  24 /**
  25  * container_of_safe - cast a member of a structure out to the containing structure
  26  * @ptr:        the pointer to the member.
  27  * @type:       the type of the container struct this is embedded in.
  28  * @member:     the name of the member within the struct.
  29  *
  30  * If IS_ERR_OR_NULL(ptr), ptr is returned unchanged.
  31  */
  32 #define container_of_safe(ptr, type, member) ({                         \
  33         void *__mptr = (void *)(ptr);                                   \
  34         static_assert(__same_type(*(ptr), ((type *)0)->member) ||       \
  35                       __same_type(*(ptr), void),                        \
  36                       "pointer type mismatch in container_of_safe()");  \
  37         IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) :                     \
  38                 ((type *)(__mptr - offsetof(type, member))); })
  39
  40 #endif  /* _LINUX_CONTAINER_OF_H */