Linux内核常用宏定义

1、offsetof

        #define offsetof(TYPE, MEMBER)    ((size_t)&((TYPE *)0)->MEMBER)

        

                 1、定义TYPE类型指针，地址为0

                  2、指向成员变量MEMBER

                  3、获取MEMBER地址

                   4、强制类型转换

        巧妙之处是首地址0，member地址就是偏移地址

2、container_of

        

/**
 * 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.
 *
 */
#define container_of(ptr, type, member) ({                \
    void *__mptr = (void *)(ptr);                    \ 定义
    BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) &&    \
             !__same_type(*(ptr), void),            \
             "pointer type mismatch in container_of()");    \
    ((type *)(__mptr - offsetof(type, member))); })