container_of

 1 /**
 2  * container_of - cast a member of a structure out to the containing structure
 3  * @ptr:    the pointer to the member.
 4  * @type:   the type of the container struct this is embedded in.
 5  * @member: the name of the member within the struct.
 6  *
 7  */
 8 #define container_of(ptr, type, member) ({           9     const typeof( ((type *)0)->member ) *__mptr = (ptr);    10     (type *)( (char *)__mptr - offsetof(type,member) );})

1 #undef offsetof
2 #ifdef __compiler_offsetof
3 #define offsetof(TYPE,MEMBER) __compiler_offsetof(TYPE,MEMBER)
4 #else
5 #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
6 #endif