Linux kernel驱动相关抽象概念及其实现 之“linux设备模型kobject，kset，ktype”

kobject，kset，ktype三个很重要的概念贯穿Linux内核驱动架构，特转载一篇博文：

（转载自http://blog.csdn.net/gdt_a20/article/details/6424597）

一、sysfs文件系统下的每个目录对应于一个kobj，kset是kobj的封装，内嵌了一个kobj，其代表kset自身，ktype代表属性操作集，但由于通用性，因此把ktype单独剥离出来，kobj，kset，ktype成为了各个驱动模型最底层的关联元素，并由此形成了sys下的各种拓扑结构。

二、关于kobject

首先看一下kobject的原型

struct kobject {
    const char      *name;         //名字
    struct list_head    entry;         //连接到kset建立层次结构
    struct kobject      *parent;       //指向父节点，面向对象的层次架构
    struct kset     *kset;
    struct kobj_type    *ktype;        //属性文件
    struct sysfs_dirent *sd;
    struct kref     kref;          //引用计数
    unsigned int state_initialized:1;      //初始化状态...
    unsigned int state_in_sysfs:1;
    unsigned int state_add_uevent_sent:1;
    unsigned int state_remove_uevent_sent:1;
    unsigned int uevent_suppress:1;
};

　　

分析一下kobject的初始化过程

初始化函数为

---int kobject_init_and_add(struct kobject *kobj, struct kobj_type *ktype,  //参数为kobject和属性结构体
             struct kobject *parent, const char *fmt, ...)
{
    va_list args;
    int retval;
    kobject_init(kobj, ktype);
    va_start(args, fmt);
    retval = kobject_add_varg(kobj, parent, fmt, args);
    va_end(args);
    return retval;
}
---void kobject_init(struct kobject *kobj, struct kobj_type *ktype)
{
    char *err_str;
    if (!kobj) {                        //kobj为NULL错误退出
        err_str = "invalid kobject pointer!";
        goto error;
    }
    if (!ktype) {                       //ktype为NULL错误退出
        err_str = "must have a ktype to be initialized properly!/n";
        goto error;
    }
    if (kobj->state_initialized) {   //如果初始化状态为1报错
        /* 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);       //初始化kobj
    kobj->ktype = ktype;            //关联obj和ktype
    return;
error:
    printk(KERN_ERR "kobject (%p): %s/n", kobj, err_str);
    dump_stack();
}
-------static void kobject_init_internal(struct kobject *kobj)
{
    if (!kobj)
        return;
    kref_init(&kobj->kref);        //计数变成1
    INIT_LIST_HEAD(&kobj->entry);  //都指向自己，prev和next
    kobj->state_in_sysfs = 0;
    kobj->state_add_uevent_sent = 0;
    kobj->state_remove_uevent_sent = 0;
    kobj->state_initialized = 1;
}
-------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);  //设置名字，名字中不能有“/”
    if (retval) {
        printk(KERN_ERR "kobject: can not set name properly!/n");
        return retval;
    }
    kobj->parent = parent;                 //设置parent，其父节点
    return kobject_add_internal(kobj);
}
----static int kobject_add_internal(struct kobject *kobj)
{
    int error = 0;
    struct kobject *parent;
    if (!kobj)
        return -ENOENT;
    if (!kobj->name || !kobj->name[0]) {             //名字不能为空
        WARN(1, "kobject: (%p): attempted to be registered with empty "
             "name!/n", kobj);
        return -EINVAL;
    }
    parent = kobject_get(kobj->parent);  //如果parent为真，则增加kobj->kref计数，也就是父节点的引用计数
    /* join kset if set, use it as parent if we do not already have one */
    if (kobj->kset) {
        if (!parent)
            parent = kobject_get(&kobj->kset->kobj);  //如果kobj-parent父节点为NULL那么就用kobj->kset->kobj
                                                                            //  作其父节点，并增加其引用计数
        kobj_kset_join(kobj);                         //把kobj的entry成员添加到kobj->kset>list的尾部，现在的层次就是
        kobj->parent = parent;                     //kobj->kset->list指向kobj->parent
    }                                                     //    ->parent 指向kset->kobj
    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);   //利用kobj创建目录和属性文件，其中会判断，如果parent为NULL那么就在sysfs_root下创建
    if (error) {
        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;
    return error;
}
---static int create_dir(struct kobject *kobj)
{
    int error = 0;
    if (kobject_name(kobj)) {
        error = sysfs_create_dir(kobj);       //创建目录
        if (!error) {
            error = populate_dir(kobj);   //创建属性文件
            if (error)
                sysfs_remove_dir(kobj);
        }
    }
    return error;
}

　　

三、关于 kset

首先看一下kset的原型

struct kset {
    struct list_head list;  //连接着他下面的kobj成员，与kobj-entry关联
    spinlock_t list_lock;
    struct kobject kobj;    //代表kset自己
    const struct kset_uevent_ops *uevent_ops;
};

　　再来看一下kset的初始化操作，kset表现为更高级一点的kobj，其初始化操作仍然是围绕其内部的kobj展开的。

struct kset *kset_create_and_add(const char *name,
                 const struct kset_uevent_ops *uevent_ops,
                 struct kobject *parent_kobj)
{
    struct kset *kset;
    int error;
    kset = kset_create(name, uevent_ops, parent_kobj);  //创建kset，关联操作函数和其父节点
    if (!kset)
        return NULL;
    error = kset_register(kset);
    if (error) {
        kfree(kset);
        return NULL;
    }
    return kset;
}
---static struct kset *kset_create(const char *name,
                const struct kset_uevent_ops *uevent_ops,
                struct kobject *parent_kobj)
{
    struct kset *kset;
    int retval;
    kset = kzalloc(sizeof(*kset), GFP_KERNEL);  //申请结构体内存
    if (!kset)
        return NULL;
    retval = kobject_set_name(&kset->kobj, name);  //设置名字
    if (retval) {
        kfree(kset);
        return NULL;
    }
    kset->uevent_ops = uevent_ops;               //关联操作函数
    kset->kobj.parent = parent_kobj;             //关联父节点
    /*
     * 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;            //关联属性文件
    kset->kobj.kset = NULL;
    return kset;
}
----int kset_register(struct kset *k)
{
    int err;
    if (!k)
        return -EINVAL;
    kset_init(k);
    err = kobject_add_internal(&k->kobj);     //调用kobj操作函数
    if (err)
        return err;
    kobject_uevent(&k->kobj, KOBJ_ADD);
    return 0;
}
----void kset_init(struct kset *k)
{
    kobject_init_internal(&k->kobj);          //调用kobj操作函数
    INIT_LIST_HEAD(&k->list);
    spin_lock_init(&k->list_lock);
}

　　四、上面给出了kobj，kset的初始化过程，以及相互产生关联的关键点，下面给出整体的一个流程图：