轉(zhuǎn)自:http://blog.chinaunix.net/uid-11319766-id-3253414.html
一。Kobject
每個(gè)在內(nèi)核中注冊(cè)的kobject都對(duì)應(yīng)于sysfs文件系統(tǒng)中的一個(gè)目錄。
kobject在文件include/linux/kobject中定義
- struct kobject {
- const char *name; //kobject的名稱
- struct list_head entry; //kobject結(jié)構(gòu)鏈表
- struct kobject *parent; //父kobject結(jié)構(gòu)體
- struct kset *kset; //kset集合
- struct kobj_type *ktype; //kobject的類型描述符
- struct sysfs_dirent *sd; //sysfs文件目錄
- struct kref kref; //kobject引用計(jì)數(shù)
- unsigned int state_initialized:1; //kobject是否初始化
- unsigned int state_in_sysfs:1; //是否已經(jīng)加入sysfs
- unsigned int state_add_uevent_sent:1;
- unsigned int state_remove_uevent_sent:1;
- unsigned int uevent_suppress:1;
- };
sysfs組織結(jié)構(gòu),進(jìn)入sysfs目錄中。有block bus class dev devices firmware fs kernel module power這些目錄。具體代表看名字差不多就可以看出。在層次結(jié)構(gòu)上,假如有一個(gè)設(shè)備A。將有一個(gè)名稱為A的目錄。A設(shè)備是在B總線上。那A設(shè)備應(yīng)該在bus目錄下的B總線下。A設(shè)備肯定會(huì)有設(shè)備的屬性(ktype),例如是音頻設(shè)備則應(yīng)該有音量屬性,則音量屬性將在A設(shè)備目錄下有個(gè)音量屬性文件。在使用設(shè)備時(shí),如果要改變音量大小,則可以寫屬性文件入音量指。得到音量大小時(shí),可以讀取屬性文件中的音量值。
二。Kobject初始化
初始化一個(gè)kobject結(jié)構(gòu)體變量,kobject_init函數(shù)(lib/kobject.c),調(diào)用此函數(shù)前應(yīng)先將kobject變量成員全部置0
- /**
- * kobject_init - initialize a kobject structure
- * @kobj: pointer to the kobject to initialize
- * @ktype: pointer to the ktype for this kobject.
- *
- * This function will properly initialize a kobject such that it can then
- * be passed to the kobject_add() call.
- *
- * After this function is called, the kobject MUST be cleaned up by a call
- * to kobject_put(), not by a call to kfree directly to ensure that all of
- * the memory is cleaned up properly.
- */
- void kobject_init(struct kobject *kobj, struct kobj_type *ktype)
- {
- char *err_str;
- if (!kobj) { //檢查kobj變量是否為空
- err_str = "invalid kobject pointer!";
- goto error;
- }
- if (!ktype) { //檢查ktype類型變量是否為空
- err_str = "must have a ktype to be initialized properly!\n";
- goto error;
- }
- if (kobj->state_initialized) { //是否已經(jīng)初始化過
- /* do not error out as sometimes we can recover */
- printk(KERN_ERR "kobject (%p): tried to init an initialized "
- "object, something is seriously wrong.\n", kobj);
- dump_stack();
- }
- kobject_init_internal(kobj); //進(jìn)一步初始化kobj內(nèi)部成員
- kobj->ktype = ktype; //將參數(shù)中傳來的ktype變量賦值給kobj的ktype變量。
- return;
- error:
- printk(KERN_ERR "kobject (%p): %s\n", kobj, err_str);
- dump_stack();
- }
分析kobject_init_internal函數(shù)(lib/kobject.c),此函數(shù)主要設(shè)置一些kobj中的一些變量
- static void kobject_init_internal(struct kobject *kobj)
- {
- if (!kobj) //kobj是否為空
- return;
- kref_init(&kobj->kref); //增加kobject的引用計(jì)數(shù),kref_set(kref, 1);
- INIT_LIST_HEAD(&kobj->entry); //初始化kobj的鏈表
- kobj->state_in_sysfs = 0; //kobject還沒有注冊(cè)到sysfs中
- kobj->state_add_uevent_sent = 0; //
- kobj->state_remove_uevent_sent = 0;
- kobj->state_initialized = 1;
- }
三。kobj_type
對(duì)象的屬性結(jié)構(gòu)體kobj_type(include/linux/kobject.h)
- struct kobj_type {
- void (*release)(struct kobject *kobj); //釋放函數(shù)(驅(qū)動(dòng)編寫時(shí)提供),此函數(shù)會(huì)被kobject_put函數(shù)調(diào)用
- struct sysfs_ops *sysfs_ops; //屬性文件的操作函數(shù)(只有讀和寫操作)
- struct attribute **default_attrs; //屬性數(shù)組
- };
1.討論kobj_type和kobject的關(guān)系,就要先說說kobject的引用。引用一個(gè)kobject使用函數(shù)kobject_get()這個(gè)函數(shù)會(huì)增加kobject的引用并返回kobject的指針。增加其引用是通過其kobject中斷哦kref變量完成的。對(duì)kobject的引用管理主要是為了知道被引用的情況,如引用不為0就不能銷毀kobject對(duì)象,引用為0時(shí)則調(diào)用相應(yīng)的釋放函數(shù)等。
- struct kobject *kobject_get(struct kobject *kobj)
- {
- if (kobj)
- kref_get(&kobj->kref);
- return kobj;
- }
- void kref_get(struct kref *kref)
- {
- WARN_ON(!atomic_read(&kref->refcount));
- atomic_inc(&kref->refcount); //將kref中的這個(gè)原子變量加1
- smp_mb__after_atomic_inc();
- }
減少一個(gè)kobject對(duì)象的引用使用函數(shù)kobject_put()。當(dāng)一個(gè)kobject對(duì)象的引用被減少到0時(shí),程序就應(yīng)該釋放這個(gè)kobject相關(guān)的資源。所以在減少引用的函數(shù)中就應(yīng)該有調(diào)用釋放資源的相關(guān)代碼,在下面內(nèi)核代碼中我們可以看到。
- void kobject_put(struct kobject *kobj)
- {
- if (kobj) {
- if (!kobj->state_initialized) //若kobj沒有初始化就不能減少其引用
- WARN(1, KERN_WARNING "kobject: '%s' (%p): is not "
- "initialized, yet kobject_put() is being "
- "called.\n", kobject_name(kobj), kobj);
- kref_put(&kobj->kref, kobject_release); //減少kref計(jì)數(shù)
- }
- }
- int kref_put(struct kref *kref, void (*release)(struct kref *kref))
- {
- WARN_ON(release == NULL); //為空警告
- WARN_ON(release == (void (*)(struct kref *))kfree); //如果release函數(shù)就是kfree,則警告(即release函數(shù)不能是簡(jiǎn)單的kfree)
- if (atomic_dec_and_test(&kref->refcount)) { //遞減原子變量并檢查其值
- release(kref); //回調(diào)release函數(shù)
- return 1;
- }
- return 0;
- }
那這個(gè)release函數(shù)在哪里保存呢,這就和kobj_type結(jié)構(gòu)有關(guān)系了。上面我們可以看到kobj_type中有一個(gè)release函數(shù)指針,就是保存在這里。每一個(gè)kobject的ktype都指向一個(gè)kobj_type,它保存了這個(gè)kobject類型的release函數(shù)指針。
四。Kset集合
1.Kset是具有相同類型的kobject集合。一個(gè)Kset集合可以表示在/sys/drivers/目錄下,表示一類驅(qū)動(dòng)程序。kobject則表示一個(gè)具體的驅(qū)動(dòng)目錄。這樣kset則可以將kobject組織成層次化結(jié)構(gòu)。
- /**
- * struct kset - a set of kobjects of a specific type, belonging to a specific subsystem.
- *
- * A kset defines a group of kobjects. They can be individually
- * different "types" but overall these kobjects all want to be grouped
- * together and operated on in the same manner. ksets are used to
- * define the attribute callbacks and other common events that happen to
- * a kobject.
- *
- * @list: the list of all kobjects for this kset
- * @list_lock: a lock for iterating over the kobjects
- * @kobj: the embedded kobject for this kset (recursion, isn't it fun...)
- * @uevent_ops: the set of uevent operations for this kset. These are
- * called whenever a kobject has something happen to it so that the kset
- * can add new environment variables, or filter out the uevents if so
- * desired.
- */
- struct kset {
- struct list_head list; //這個(gè)鏈表存放這個(gè)kset關(guān)聯(lián)的所有kobject
- spinlock_t list_lock; //維護(hù)此鏈表的鎖
- struct kobject kobj; //內(nèi)嵌的kobject。這樣kset本身也是一個(gè)kobject也被表現(xiàn)為一個(gè)目錄
- struct kset_uevent_ops *uevent_ops; //支持熱插拔事件的函數(shù)集
- };
kset中的kobject對(duì)象,所有屬于這個(gè)kset集合的kobject對(duì)象的parent指針,均指向這個(gè)內(nèi)嵌的kobject,也即表示在一個(gè)kset集合中的kobject是相同類型的他們有相同的parent對(duì)象。kset的引用計(jì)數(shù)也就是內(nèi)嵌的kobject的引用計(jì)數(shù)。
所以kobject和kset的關(guān)系簡(jiǎn)單來講,就是
1.kset是kobject的一個(gè)頂層容器,它包含了相同類型的kobject,kset中有鏈表成員保存所有的kobject指向。
2.kobject中的kset指針指向了一個(gè)kset
3.kset中有kobject對(duì)象,表明了kset也可以有kobject相關(guān)的操作。
4.kset鏈表中的kobject對(duì)象的parent指針一般都指向kset內(nèi)嵌的kobject對(duì)象。
kset和kobject關(guān)系基本如下圖,
kset_uevent_ops熱插拔事件
熱插拔事件是用內(nèi)核空間發(fā)送到用戶空間的通知。表明內(nèi)核中的某些配置已經(jīng)發(fā)生變化。用戶空間則會(huì)根據(jù)這些信息做相應(yīng)的處理。例如,U盤插入U(xiǎn)SB系統(tǒng)時(shí),會(huì)產(chǎn)生一個(gè)熱插拔事件,內(nèi)核會(huì)捕捉到這個(gè)熱插拔事件,然后調(diào)用/sbin/hotplug程序,該程序通知加載驅(qū)動(dòng)程序來相應(yīng)U盤的插入動(dòng)作。
熱插拔函數(shù)集的定義在include/linux/koject.h中
- struct kset_uevent_ops {
- int (*filter)(struct kset *kset, struct kobject *kobj); //事件過濾函數(shù)
- const char *(*name)(struct kset *kset, struct kobject *kobj); //事件名稱函數(shù)
- int (*uevent)(struct kset *kset, struct kobject *kobj,struct kobj_uevent_env *env);
- //uevent函數(shù)可在熱插拔程序執(zhí)行前,向環(huán)境變量寫值
- };
詳細(xì)的熱插拔事件先不在這里分析。
2.注冊(cè)一個(gè)kset
- /**
- * kset_register - initialize and add a kset.
- * @k: kset.
- */
- int kset_register(struct kset *k)
- {
- int err;
- if (!k)
- return -EINVAL;
- kset_init(k);
- err = kobject_add_internal(&k->kobj); //將kset中的kobject添加進(jìn)sysfs,函數(shù)將在后面講解
- if (err)
- return err;
- kobject_uevent(&k->kobj, KOBJ_ADD);
- return 0;
- }
- /**
- * kset_init - initialize a kset for use
- * @k: kset
- */
- void kset_init(struct kset *k)
- {
- kobject_init_internal(&k->kobj);
- INIT_LIST_HEAD(&k->list);
- spin_lock_init(&k->list_lock);
- }
我們使用函數(shù)kset_create_and_add()還可以一次性將kset創(chuàng)建并注冊(cè)進(jìn)sysyfs
- /**
- * kset_create_and_add - create a struct kset dynamically and add it to sysfs
- *
- * @name: the name for the kset
- * @uevent_ops: a struct kset_uevent_ops for the kset
- * @parent_kobj: the parent kobject of this kset, if any.
- *
- * This function creates a kset structure dynamically and registers it
- * with sysfs. When you are finished with this structure, call
- * kset_unregister() and the structure will be dynamically freed when it
- * is no longer being used.
- *
- * If the kset was not able to be created, NULL will be returned.
- */
- struct kset *kset_create_and_add(const char *name,
- struct kset_uevent_ops *uevent_ops,
- struct kobject *parent_kobj)
- {
- struct kset *kset;
- int error;
- kset = kset_create(name, uevent_ops, parent_kobj); //根據(jù)參數(shù)創(chuàng)建一個(gè)kset
- if (!kset)
- return NULL;
- error = kset_register(kset); //將kset注冊(cè)進(jìn)sysfs,函數(shù)在上面已經(jīng)分析過
- if (error) {
- kfree(kset);
- return NULL;
- }
- return kset;
- }
- /**
- * kset_create - create a struct kset dynamically
- *
- * @name: the name for the kset
- * @uevent_ops: a struct kset_uevent_ops for the kset
- * @parent_kobj: the parent kobject of this kset, if any.
- *
- * This function creates a kset structure dynamically. This structure can
- * then be registered with the system and show up in sysfs with a call to
- * kset_register(). When you are finished with this structure, if
- * kset_register() has been called, call kset_unregister() and the
- * structure will be dynamically freed when it is no longer being used.
- *
- * If the kset was not able to be created, NULL will be returned.
- */
- static struct kset *kset_create(const char *name,
- struct kset_uevent_ops *uevent_ops,
- struct kobject *parent_kobj)
- {
- struct kset *kset;
- int retval;
- kset = kzalloc(sizeof(*kset), GFP_KERNEL);
- if (!kset)
- return NULL;
- retval = kobject_set_name(&kset->kobj, name); //設(shè)置kobject名稱
- if (retval) {
- kfree(kset);
- return NULL;
- }
- kset->uevent_ops = uevent_ops;
- kset->kobj.parent = parent_kobj; //設(shè)置kset的kobject的父對(duì)象
- /*
- * The kobject of this kset will have a type of kset_ktype and belong to
- * no kset itself. That way we can properly free it when it is
- * finished being used.
- */
- kset->kobj.ktype = &kset_ktype; //設(shè)置kset的kobject的默認(rèn)屬性
- kset->kobj.kset = NULL;
- return kset;
- }
上面這些函數(shù)主要包含即調(diào)用關(guān)系如下,
kset_create_and_add
kset_create
kzalloc
kset_register
kset_init
kobject_add_internal
kset中嵌入了一個(gè)kobject,所以還有一些和kobject相似的函數(shù)如,
增加kset的引用,實(shí)際是調(diào)用kobject_get增加kset中的kobject的引用
- static inline struct kset *kset_get(struct kset *k)
- {
- return k ? to_kset(kobject_get(&k->kobj)) : NULL;
- }
減少kset的引用,實(shí)際是調(diào)用kobject_put減少kset中的kobject的引用
- static inline void kset_put(struct kset *k)
- {
- kobject_put(&k->kobj);
- }
順便提一下,子系統(tǒng)subsystem,在新的內(nèi)核中已經(jīng)沒有這個(gè)結(jié)構(gòu)了。在原來的內(nèi)核中它用來表示比kset更高一層的容器,kset應(yīng)該屬于一個(gè)子系統(tǒng),子系統(tǒng)幫助內(nèi)核在分層結(jié)構(gòu)中定位kset。內(nèi)核子系統(tǒng)包括 block_subsys(/sys/block 塊設(shè)備)、 devices_subsys(/sys/devices 核心設(shè)備層)。現(xiàn)在subsystem已經(jīng)被kset代替了。
五,將kobject注冊(cè)進(jìn)sysfs系統(tǒng)
我們?cè)诳匆幌氯绾螌object注冊(cè)進(jìn)sysfs系統(tǒng)中。使用函數(shù)kobject_init_and_add()(lib/kobject.c)函數(shù)將一個(gè)kobject注冊(cè)進(jìn)sysfs系統(tǒng),在/sys中表現(xiàn)為生成一個(gè)相應(yīng)的目錄。
- /**
- * kobject_init_and_add - initialize a kobject structure and add it to the kobject hierarchy
- * @kobj: pointer to the kobject to initialize
- * @ktype: pointer to the ktype for this kobject.
- * @parent: pointer to the parent of this kobject.
- * @fmt: the name of the kobject.
- *
- * This function combines the call to kobject_init() and
- * kobject_add(). The same type of error handling after a call to
- * kobject_add() and kobject lifetime rules are the same here.
- */
- int kobject_init_and_add(struct kobject *kobj, struct kobj_type *ktype,
- struct kobject *parent, const char *fmt, ...)
- {
- va_list args;
- int retval;
- kobject_init(kobj, ktype); //調(diào)用初始化函數(shù)先初始化kobject變量
- va_start(args, fmt); //解析可變參數(shù)列表
- retval = kobject_add_varg(kobj, parent, fmt, args); //給kobject添加參數(shù),并且將其添加到sysfs系統(tǒng)。
- va_end(args); //結(jié)束解析參數(shù)列表
- return retval;
- }
- static int kobject_add_varg(struct kobject *kobj, struct kobject *parent, const char *fmt, va_list vargs)
- {
- int retval;
- retval = kobject_set_name_vargs(kobj, fmt, vargs); //設(shè)置kobject的名稱
- if (retval) {
- printk(KERN_ERR "kobject: can not set name properly!\n");
- return retval;
- }
- kobj->parent = parent; //設(shè)置kobject的父kobject
- return kobject_add_internal(kobj); //添加kobject
- }
- static int kobject_add_internal(struct kobject *kobj)
- {
- int error = 0;
- struct kobject *parent;
- if (!kobj) //檢查是否為空
- return -ENOENT;
- if (!kobj->name || !kobj->name[0]) { //kobj是否有名稱,如果沒有則不能注冊(cè),生成目錄。
- WARN(1, "kobject: (%p): attempted to be registered with empty "
- "name!\n", kobj);
- return -EINVAL;
- }
- parent = kobject_get(kobj->parent); //獲得父kobject,并增加父kobject的引用計(jì)數(shù)
- /* join kset if set, use it as parent if we do not already have one */
- if (kobj->kset) { //是否有kset集合
- if (!parent) //如果沒有父kobject則用kset中的kobject對(duì)象
- parent = kobject_get(&kobj->kset->kobj);
- kobj_kset_join(kobj); //將kobject添加進(jìn)它關(guān)聯(lián)的kset的list鏈表中。
- kobj->parent = parent; //設(shè)置父koject
- }
- pr_debug("kobject: '%s' (%p): %s: parent: '%s', set: '%s'\n",
- kobject_name(kobj), kobj, __func__,
- parent ? kobject_name(parent) : "<NULL>",
- kobj->kset ? kobject_name(&kobj->kset->kobj) : "<NULL>");
- error = create_dir(kobj); //創(chuàng)建kobject的相應(yīng)目錄
-
- if (error) { //創(chuàng)建時(shí)出錯(cuò)處理
- kobj_kset_leave(kobj);
- kobject_put(parent);
- kobj->parent = NULL;
- /* be noisy on error issues */
- if (error == -EEXIST)
- printk(KERN_ERR "%s failed for %s with "
- "-EEXIST, don't try to register things with "
- "the same name in the same directory.\n",
- __func__, kobject_name(kobj));
- else
- printk(KERN_ERR "%s failed for %s (%d)\n",
- __func__, kobject_name(kobj), error);
- dump_stack();
- } else
- kobj->state_in_sysfs = 1; //標(biāo)記為已經(jīng)注冊(cè)進(jìn)sysfs
- return error;
- }
sysfs創(chuàng)建目錄函數(shù)create_dir,在lib/kobject.c
- static int create_dir(struct kobject *kobj)
- {
- int error = 0;
- if (kobject_name(kobj)) {
- error = sysfs_create_dir(kobj); //在sysfs中創(chuàng)建目錄,將來有時(shí)間了可以分析下sysfs子系統(tǒng)。
- if (!error) {
- error = populate_dir(kobj);
- if (error)
- sysfs_remove_dir(kobj);
- }
- }
- return error;
- }
以上函數(shù)的主要調(diào)用關(guān)系,如下
kobject_init_and_add
kobject_init
kobject_add_varg
kobject_add_internal
create_dir
還有一個(gè)函數(shù)kobject_add,也可以添加一個(gè)kobject,它只是沒有kobject_init這一步。
- int kobject_add(struct kobject *kobj, struct kobject *parent,
- const char *fmt, ...)
- {
- va_list args;
- int retval;
- if (!kobj)
- return -EINVAL;
- if (!kobj->state_initialized) {
- printk(KERN_ERR "kobject '%s' (%p): tried to add an "
- "uninitialized object, something is seriously wrong.\n",
- kobject_name(kobj), kobj);
- dump_stack();
- return -EINVAL;
- }
- va_start(args, fmt);
- retval = kobject_add_varg(kobj, parent, fmt, args);
- va_end(args);
- return retval;
- }