linux设备模型

device_driver和device必须依附总线。总线、驱动、设备最终会落实为sysfs中的一个目录。kobject对应sysfs的一个目录。

attribute直接落实sysfs中的一个文件，如果attribute非常多，show/sore函数里的分支会很凌乱。解决这个问题，提供kobj——attribute：

struct

struct kobj_attribute{

struct  attribute attr;
ssize_t (*show)(struct kobject *kobj,struct kobj_attribute *attr, char *buf);
ssize_t (*store)(struct kobject *kobj,struct kobj_attribute *attr ,const char *buf, size_t count);

};

每一个attribute会对 应自己的show、store函数，这样就极大的提高了灵活性 。sysfs是通过kobject里的kobj_type->sysfs_ops来读写attribute的，那如果利用kobj_attribute中的show/store来读写attribute，就必须在kobj_type->sysfs_ops里面指定。

static ssize_t kobj_attr_show(struct kobjct *kobj, struct attribute *attr,char *buf )
{

struct kobj_attribute *kattr;
ssize _t ret=-EIO;
kattr=container_of(attr,struct kobj_attribute,attr);
if(kattr->show)
ret=kattr->show(kobj,kattr,buf);
return ret;

}static ssize_t kobj_attr_store(struct kobject *kobj, struct attribute *attr,

                   const char *buf, size_t count)

{

    struct kobj_attribute *kattr;

    ssize_t ret = -EIO;

    kattr = container_of(attr, struct kobj_attribute, attr);

    if (kattr->store)

        ret = kattr->store(kobj, kattr, buf, count);

    return ret;

}
const struct sysfs_ops kobj_sysfs_ops = {

    .show   = kobj_attr_show,

    .store  = kobj_attr_store,

};
static void dynamic_kobj_release(struct kobject *kobj)

{

    pr_debug("kobject: (%p): %s\n", kobj, __func__);

    kfree(kobj);

}
static struct kobj_type dynamic_kobj_ktype = {

    .release    = dynamic_kobj_release,

    .sysfs_ops  = &kobj_sysfs_ops,

}; 

kobj_attribute是内核提供的更加灵活的attribute方式还要使用kobject_create来创建kobject。

struct my_attributte{

struct attribute attr;
ssize_t (*sbow)(struct my_kobj kobj, struct my_attribute *attr,char *buf);
ssize_t(*store)(struct my_kobj *obj,struct my_attribute *attr,char *buf,size_t count);

}

先创建接口：sysfs_creat_group(&xxdev->dev.kobj,&dev_attr_grp);

封装：static struct attribute_group dev_attr_grp={.attrs=dev_attrs,}

结构体：static Strut attribute *dev_attrs[]={&dev_attr_polling.attr,null,}

节点：static device_attr(polling,666,show_polling,set_polling).

读写：size_t show_polling(kobj,attribute,buf);