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kobject: update documentation 

Update kobject documentation:

- Update structure definitions.
- Remove documentation of removed struct subsystem.

(First shot, uevent_ops probably need some documentation as well.)

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
hifive-unleashed-5.1
Cornelia Huck 2007-07-27 13:41:10 +02:00 committed by Greg Kroah-Hartman
parent a56156489d
commit f285ea0580
1 changed files with 59 additions and 119 deletions
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178
Documentation/kobject.txt
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@ -27,7 +27,6 @@ in detail, and briefly here:
- kobjects a simple object.
- kset a set of objects of a certain type.
- ktype a set of helpers for objects of a common type.
- subsystem a controlling object for a number of ksets.
The kobject infrastructure maintains a close relationship with the
@ -54,13 +53,15 @@ embedded in larger data structures and replace fields they duplicate.
1.2 Definition
struct kobject {
const char * k_name;
char name[KOBJ_NAME_LEN];
atomic_t refcount;
struct kref kref;
struct list_head entry;
struct kobject * parent;
struct kset * kset;
struct kobj_type * ktype;
struct dentry * dentry;
struct sysfs_dirent * sd;
wait_queue_head_t poll;
};
void kobject_init(struct kobject *);
@ -137,8 +138,7 @@ If a kobject does not have a parent when it is registered, its parent
becomes its dominant kset.
If a kobject does not have a parent nor a dominant kset, its directory
is created at the top-level of the sysfs partition. This should only
happen for kobjects that are embedded in a struct subsystem.
is created at the top-level of the sysfs partition.
@ -150,10 +150,10 @@ A kset is a set of kobjects that are embedded in the same type.
struct kset {
struct subsystem * subsys;
struct kobj_type * ktype;
struct list_head list;
struct kobject kobj;
struct kset_uevent_ops * uevent_ops;
};
@ -169,8 +169,7 @@ struct kobject * kset_find_obj(struct kset *, char *);
The type that the kobjects are embedded in is described by the ktype
pointer. The subsystem that the kobject belongs to is pointed to by the
subsys pointer.
pointer.
A kset contains a kobject itself, meaning that it may be registered in
the kobject hierarchy and exported via sysfs. More importantly, the
@ -209,6 +208,58 @@ the hierarchy.
kset_find_obj() may be used to locate a kobject with a particular
name. The kobject, if found, is returned.
There are also some helper functions which names point to the formerly
existing "struct subsystem", whose functions have been taken over by
ksets.
decl_subsys(name,type,uevent_ops)
Declares a kset named '<name>_subsys' of type <type> with
uevent_ops <uevent_ops>. For example,
decl_subsys(devices, &ktype_device, &device_uevent_ops);
is equivalent to doing:
struct kset devices_subsys = {
.kobj = {
.name = "devices",
},
.ktype = &ktype_devices,
.uevent_ops = &device_uevent_ops,
};
The objects that are registered with a subsystem that use the
subsystem's default list must have their kset ptr set properly. These
objects may have embedded kobjects or ksets. The
following helpers make setting the kset easier:
kobj_set_kset_s(obj,subsys)
- Assumes that obj->kobj exists, and is a struct kobject.
- Sets the kset of that kobject to the kset <subsys>.
kset_set_kset_s(obj,subsys)
- Assumes that obj->kset exists, and is a struct kset.
- Sets the kset of the embedded kobject to the kset <subsys>.
subsys_set_kset(obj,subsys)
- Assumes obj->subsys exists, and is a struct subsystem.
- Sets obj->subsys.kset.kobj.kset to the subsystem's embedded kset.
void subsystem_init(struct kset *s);
int subsystem_register(struct kset *s);
void subsystem_unregister(struct kset *s);
struct kset *subsys_get(struct kset *s);
void kset_put(struct kset *s);
These are just wrappers around the respective kset_* functions.
2.3 sysfs
@ -254,114 +305,3 @@ Instances of struct kobj_type are not registered; only referenced by
the kset. A kobj_type may be referenced by an arbitrary number of
ksets, as there may be disparate sets of identical objects.
4. subsystems
4.1 Description
A subsystem represents a significant entity of code that maintains an
arbitrary number of sets of objects of various types. Since the number
of ksets and the type of objects they contain are variable, a
generic representation of a subsystem is minimal.
struct subsystem {
struct kset kset;
struct rw_semaphore rwsem;
};
int subsystem_register(struct subsystem *);
void subsystem_unregister(struct subsystem *);
struct subsystem * subsys_get(struct subsystem * s);
void subsys_put(struct subsystem * s);
A subsystem contains an embedded kset so:
- It can be represented in the object hierarchy via the kset's
embedded kobject.
- It can maintain a default list of objects of one type.
Additional ksets may attach to the subsystem simply by referencing the
subsystem before they are registered. (This one-way reference means
that there is no way to determine the ksets that are attached to the
subsystem.)
All ksets that are attached to a subsystem share the subsystem's R/W
semaphore.
4.2 subsystem Programming Interface.
The subsystem programming interface is simple and does not offer the
flexibility that the kset and kobject programming interfaces do. They
may be registered and unregistered, as well as reference counted. Each
call forwards the calls to their embedded ksets (which forward the
calls to their embedded kobjects).
4.3 Helpers
A number of macros are available to make dealing with subsystems and
their embedded objects easier.
decl_subsys(name,type)
Declares a subsystem named '<name>_subsys', with an embedded kset of
type <type>. For example,
decl_subsys(devices,&ktype_devices);
is equivalent to doing:
struct subsystem device_subsys = {
.kset = {
.kobj = {
.name = "devices",
},
.ktype = &ktype_devices,
}
};
The objects that are registered with a subsystem that use the
subsystem's default list must have their kset ptr set properly. These
objects may have embedded kobjects, ksets, or other subsystems. The
following helpers make setting the kset easier:
kobj_set_kset_s(obj,subsys)
- Assumes that obj->kobj exists, and is a struct kobject.
- Sets the kset of that kobject to the subsystem's embedded kset.
kset_set_kset_s(obj,subsys)
- Assumes that obj->kset exists, and is a struct kset.
- Sets the kset of the embedded kobject to the subsystem's
embedded kset.
subsys_set_kset(obj,subsys)
- Assumes obj->subsys exists, and is a struct subsystem.
- Sets obj->subsys.kset.kobj.kset to the subsystem's embedded kset.
4.4 sysfs
subsystems are represented in sysfs via their embedded kobjects. They
follow the same rules as previously mentioned with no exceptions. They
typically receive a top-level directory in sysfs, except when their
embedded kobject is part of another kset, or the parent of the
embedded kobject is explicitly set.
Note that the subsystem's embedded kset must be 'attached' to the
subsystem itself in order to use its rwsem. This is done after
kset_add() has been called. (Not before, because kset_add() uses its
subsystem for a default parent if it doesn't already have one).