kobject: documentation: Fix erroneous example in kobject doc.

Replace uio_mem example for kobjects with uio_map, since the uio_mem
struct no longer contains a kobject.
Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Documentation/kobject.txt

@@ -59,18 +59,20 @@ nice to have in other objects.  The C language does not allow for the
 direct expression of inheritance, so other techniques - such as structure
 embedding - must be used.
 
-So, for example, the UIO code has a structure that defines the memory
-region associated with a uio device:
+(As an aside, for those familiar with the kernel linked list implementation,
+this is analogous as to how "list_head" structs are rarely useful on
+their own, but are invariably found embedded in the larger objects of
+interest.)
 
-struct uio_mem {
+So, for example, the UIO code in drivers/uio/uio.c has a structure that
+defines the memory region associated with a uio device:
+
+    struct uio_map {
 	struct kobject kobj;
-	unsigned long addr;
-	unsigned long size;
-	int memtype;
-	void __iomem *internal_addr;
-};
+	struct uio_mem *mem;
+    };
 
-If you have a struct uio_mem structure, finding its embedded kobject is
+If you have a struct uio_map structure, finding its embedded kobject is
 just a matter of using the kobj member.  Code that works with kobjects will
 often have the opposite problem, however: given a struct kobject pointer,
 what is the pointer to the containing structure?  You must avoid tricks
@@ -79,17 +81,34 @@ and, instead, use the container_of() macro, found in <linux/kernel.h>:
 
     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 given type. So, for example, a pointer "kp" to a struct kobject
-embedded within a struct uio_mem could be converted to a pointer to the
-containing uio_mem structure with:
+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;
+    };
+
+    #define to_map(map) container_of(map, struct uio_map, kobj)
 
-    struct uio_mem *u_mem = container_of(kp, struct uio_mem, kobj);
+where the macro argument "map" is a pointer to the struct kobject in
+question.  That macro is subsequently invoked with:
 
-Programmers often define a simple macro for "back-casting" kobject pointers
-to the containing type.
+    struct uio_map *map = to_map(kobj);
 
 
 Initialization of kobjects