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 ,constchar *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,
constchar *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;
}
conststruct sysfs_ops kobj_sysfs_ops = {
.show = kobj_attr_show,
.store = kobj_attr_store,
};
staticvoid dynamic_kobj_release(struct kobject *kobj)
{
pr_debug("kobject: (%p): %sn", kobj, __func__);
kfree(kobj);
}
staticstruct 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);
原文：http://www.cnblogs.com/xjh-2016/p/5459159.html
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