+ container_of(pointer, type, member)
+
+where:
+
+ * "pointer" is the pointer to the embedded kobject,
+ * "type" is the type of the containing structure, and
+ * "member" is the name of the structure field to which "pointer" points.
+
+The return value from container_of() is a pointer to the corresponding
+container type. So, for example, a pointer "kp" to a struct kobject
+embedded *within* a struct uio_map could be converted to a pointer to the
+*containing* uio_map structure with:
+
+ struct uio_map *u_map = container_of(kp, struct uio_map, kobj);
+
+For convenience, programmers often define a simple macro for "back-casting"
+kobject pointers to the containing type. Exactly this happens in the
+earlier drivers/uio/uio.c, as you can see here:
+
+ struct uio_map {
+ struct kobject kobj;
+ struct uio_mem *mem;
+ };