kobject: Introduce struct kobj_type.

This is the first step in morphing struct subsystem into something meaningful.

A subsystem is defined simply as a list of kobjects of a certain type, which
is far too generic. A subsystem should be representative of a large entity
of code (i.e. a subsystem of the kernel), not just a simple list. 

This changeset:

- Creates struct kobj_type, a descriptor of the type a kobject is embedded
  in.

- Extracts the fields that are specific to a particular object type from
  struct subsystem and puts them in struct kobj_type, which are
  - the object's release method.
  - the sysfs operations for the object type.
  - the default attributes of the object type.

- Adds ptr to struct kobject to point to its type descriptor. 

- Converts the existing subsystem definitions to define struct kobj_type. 


struct kobj_type's are not registered, as they do not have any explicit
representation in the object hierarchy, nor do they have any fields that
need runtime initialization. 

A kobject's ktype should be set when it is registered, like its subsystem.
Note this obviates the need for defining a struct subsystem when an object
type does not need to be kept in a global list. 

1 files changed, 6 insertions, 5 deletions

diff --git a/lib/kobject.c b/lib/kobject.c
index 24807bc72f81..f2f38b092a6a 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -25,13 +25,13 @@ static spinlock_t kobj_lock = SPIN_LOCK_UNLOCKED;
 
 static int populate_dir(struct kobject * kobj)
 {
-	struct subsystem * s = kobj->subsys;
+	struct kobj_type * t = kobj->ktype;
 	struct attribute * attr;
 	int error = 0;
 	int i;
 	
-	if (s && s->default_attrs) {
-		for (i = 0; (attr = s->default_attrs[i]); i++) {
+	if (t && t->default_attrs) {
+		for (i = 0; (attr = t->default_attrs[i]); i++) {
 			if ((error = sysfs_create_file(kobj,attr)))
 				break;
 		}
@@ -173,17 +173,18 @@ struct kobject * kobject_get(struct kobject * kobj)
 
 void kobject_cleanup(struct kobject * kobj)
 {
+	struct kobj_type * t = kobj->ktype;
 	struct subsystem * s = kobj->subsys;
 
 	pr_debug("kobject %s: cleaning up\n",kobj->name);
 	if (s) {
 		down_write(&s->rwsem);
 		list_del_init(&kobj->entry);
-		if (s->release)
-			s->release(kobj);
 		up_write(&s->rwsem);
 		subsys_put(s);
 	}
+	if (t && t->release)
+		t->release(kobj);
 }
 
 /**