从上面代码可以看出,在platform_driver中设置了probe, remove, shutdown, suspend或resume函数的话
printk(KERN_WARNING "Driver '%s' needs updating - please use ""bus_type methods\n", drv->name);
printk(KERN_ERR "Error: Driver '%s' is already registered, “"aborting...\n", drv->name);
pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);
//设置私有数据的父容器,在这一步中,设置了kset为platform下的drivers_kset结构,也就是drivers呢个目录
//初始化kobj对象,设置容器操作集并建立相应的目录,这里由于没有提供parent,所以会使用父容器中的kobj为父对象
error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
//为真则进行与设备的匹配,到这里,就会与我们之前注册的test_device连接上了,至于如何连接,进行了什么操作,将在别的文章中详细描述
printk(KERN_ERR "%s: driver_add_attrs(%s) failed\n",__func__, drv->name);
printk(KERN_ERR "%s: add_bind_files(%s) failed\n",__func__, drv->name);
先说说关系,ktype与kobject和kset这两者之前的关系较少,让我画一个图,是这样的
ktype依赖于kobject,kset也依赖于kobject,而kobject有时需要kset(所以用了一个白箭头),不一定需要ktype(真可怜,连白箭头都没有)
首先先说一下这个可有可无的ktype
到/sys/bus/platform下面可以看见一个drivers_autoprobe的文件
cat drivers_autoprobe可以查看这个文件的值
echo 0 > drivers_autoprobe则可以改变这个文件的值
drivers_autoprobe这个文件表示的是是否自动进行初始化
在
void bus_attach_device(struct device *dev)
{
struct bus_type *bus = dev->bus;
int ret = 0;
if (bus) {
if (bus->p->drivers_autoprobe)
ret = device_attach(dev);
WARN_ON(ret < 0);
if (ret >= 0)
klist_add_tail(&dev->knode_bus, &bus->p->klist_devices);
}
}
中可以看见这么一段代码
if (bus->p->drivers_autoprobe)
ret = device_attach(dev);
bus->p->drivers_autoprobe的值为真则进行匹配
而drivers_autoprobe这个文件则可以动态的修改这个值选择是否进行匹配
使用外部文件修改内核参数,ktype就是提供了这么一种方法
现在让我们看看ktype是怎么通过kobject进行运作的
首先是ktype及通过ktype进行运作的drivers_autoprobe的注册
ktype的挂载十分简单,因为他是和kobject是一体的
只有这么下面一句
priv->subsys.kobj.ktype = &bus_ktype;
这样就将bus_ktype挂载到了platform_bus_type的kobject上
drivers_autoprobe的注册如下
retval = bus_create_file(bus, &bus_attr_drivers_autoprobe);
bus_attr_drivers_autoprobe这个结构由一系列的宏进行组装
static BUS_ATTR(drivers_autoprobe, S_IWUSR | S_IRUGO,
show_drivers_autoprobe, store_drivers_autoprobe);
#define BUS_ATTR(_name, _mode, _show, _store) \
struct bus_attribute bus_attr_##_name = __ATTR(_name, _mode, _show, _store)
#define __ATTR(_name,_mode,_show,_store) { \
.attr = {.name = __stringify(_name), .mode = _mode }, \
.show = _show, \
.store = _store, \
}
最后bus_attr_drivers_autoprobe的模型如下
struct bus_attribute bus_attr_drivers_autoprobe
{
.attr = {
.name = “drivers_autoprobe”,
.mode = S_IWUSR | S_IRUGO
},
.show = show_drivers_autoprobe,
.store = store_drivers_autoprobe,
}
进入到bus_create_file中
int bus_create_file(struct bus_type *bus, struct bus_attribute *attr)
//参数为(bus, &bus_attr_drivers_autoprobe)
{
int error;
if (bus_get(bus)) {
error = sysfs_create_file(&bus->p->subsys.kobj, &attr->attr);
bus_put(bus);
} else
error = -EINVAL;
return error;
}
int sysfs_create_file(struct kobject * kobj, const struct attribute * attr)
//参数为(&bus->p->subsys.kobj, &attr->attr)
{
BUG_ON(!kobj || !kobj->sd || !attr);
return sysfs_add_file(kobj->sd, attr, SYSFS_KOBJ_ATTR);
}
int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,int type)
//参数为(&bus->p->subsys.kobj ->sd, &attr->attr, SYSFS_KOBJ_ATTR)
{
return sysfs_add_file_mode(dir_sd, attr, type, attr->mode);
}
int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
const struct attribute *attr, int type, mode_t amode)
//整理一下参数,现在应该为
//(&platform_bus_type->p->subsys.kobj ->sd, &bus_attr_drivers_autoprobe->attr, SYSFS_KOBJ_ATTR, &bus_attr_drivers_autoprobe->attr->mode)
{
umode_t mode = (amode & S_IALLUGO) | S_IFREG;
struct sysfs_addrm_cxt acxt;
struct sysfs_dirent *sd;
int rc;
//在这一步中可以看出新建了一个节点
sd = sysfs_new_dirent(attr->name, mode, type);
if (!sd)
return -ENOMEM;
//这一步挂载了&bus_attr_drivers_autoprobe->attr到节点中,为以后提取attr及上层结构做准备
sd->s_attr.attr = (void *)attr;
// dir_sd也就是上层目录,在这里为platform_bus_type->p->subsys.kobj ->sd
//也就是/sys/bus/platform这个目录
sysfs_addrm_start(&acxt, dir_sd);
rc = sysfs_add_one(&acxt, sd);
sysfs_addrm_finish(&acxt);
if (rc)
sysfs_put(sd);
return rc;
}
struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
{
char *dup_name = NULL;
struct sysfs_dirent *sd;
if (type & SYSFS_COPY_NAME) {
name = dup_name = kstrdup(name, GFP_KERNEL);
if (!name)
return NULL;
}
sd = kmem_cache_zalloc(sysfs_dir_cachep, GFP_KERNEL);
if (!sd)
goto err_out1;
if (sysfs_alloc_ino(&sd->s_ino))
goto err_out2;
atomic_set(&sd->s_count, 1);
atomic_set(&sd->s_active, 0);
sd->s_name = name; //节点的名字为&bus_attr_drivers_autoprobe->attr->name 也就是drivers_autoprobe
sd->s_mode = mode;
sd->s_flags = type; //节点的type为SYSFS_KOBJ_ATTR
return sd;
err_out2:
kmem_cache_free(sysfs_dir_cachep, sd);
err_out1:
kfree(dup_name);
return NULL;
}
现在一切准备就绪,来看看怎么读取吧
首先是open,大概流程可以看我的另一篇文章<从文件到设备>,一直看到ext3_lookup
这里和ext3_lookup不同的是,sys的文件系统是sysfs文件系统,所以应该使用的lookup函数为sysfs_lookup(/fs/sysfs/dir.c)
static struct dentry * sysfs_lookup(struct inode *dir, struct dentry *dentry,
struct nameidata *nd)
{
struct dentry *ret = NULL;
struct sysfs_dirent *parent_sd = dentry->d_parent->d_fsdata;
struct sysfs_dirent *sd;
struct inode *inode;
mutex_lock(&sysfs_mutex);
sd = sysfs_find_dirent(parent_sd, dentry->d_name.name);
if (!sd) {
ret = ERR_PTR(-ENOENT);
goto out_unlock;
}
//节点的初始化在这里
inode = sysfs_get_inode(sd);
if (!inode) {
ret = ERR_PTR(-ENOMEM);
goto out_unlock;
}
dentry->d_op = &sysfs_dentry_ops;
dentry->d_fsdata = sysfs_get(sd);
d_instantiate(dentry, inode);
d_rehash(dentry);
out_unlock:
mutex_unlock(&sysfs_mutex);
return ret;
}
struct inode * sysfs_get_inode(struct sysfs_dirent *sd)
{
struct inode *inode;
inode = iget_locked(sysfs_sb, sd->s_ino);
if (inode && (inode->i_state & I_NEW))
//为节点赋值
sysfs_init_inode(sd, inode);
return inode;
}
static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
{
struct bin_attribute *bin_attr;
inode->i_blocks = 0;
inode->i_mapping->a_ops = &sysfs_aops;
inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
inode->i_op = &sysfs_inode_operations;
inode->i_ino = sd->s_ino;
lockdep_set_class(&inode->i_mutex, &sysfs_inode_imutex_key);
if (sd->s_iattr) {
set_inode_attr(inode, sd->s_iattr);
} else
set_default_inode_attr(inode, sd->s_mode);
//判断类型
switch (sysfs_type(sd)) {
case SYSFS_DIR:
inode->i_op = &sysfs_dir_inode_operations;
inode->i_fop = &sysfs_dir_operations;
inode->i_nlink = sysfs_count_nlink(sd);
break;
//还记得在注册的时候有一个参数为SYSFS_KOBJ_ATTR赋到了sd->s_flags上面吧
case SYSFS_KOBJ_ATTR:
inode->i_size = PAGE_SIZE;
inode->i_fop = &sysfs_file_operations;
break;
case SYSFS_KOBJ_BIN_ATTR:
bin_attr = sd->s_bin_attr.bin_attr;
inode->i_size = bin_attr->size;
inode->i_fop = &bin_fops;
break;
case SYSFS_KOBJ_LINK:
inode->i_op = &sysfs_symlink_inode_operations;
break;
default:
BUG();
}
unlock_new_inode(inode);
}
sysfs_file_operations的结构如下,之后open和read,write都明了了
const struct file_operations sysfs_file_operations = {
.read = sysfs_read_file,
.write = sysfs_write_file,
.llseek = generic_file_llseek,
.open = sysfs_open_file,
.release = sysfs_release,
.poll = sysfs_poll,
};
有关在哪调用open还是请查阅我的另一篇文章<从文件到设备>中 nameidata_to_filp之后的操作
好的~ 现在进入到了sysfs_open_file中
static int sysfs_open_file(struct inode *inode, struct file *file)
{
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
//要重的取值,在这里取得了drivers_autoprobe的目录platform的kproject
struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
struct sysfs_buffer *buffer;
struct sysfs_ops *ops;
int error = -EACCES;
if (!sysfs_get_active_two(attr_sd))
return -ENODEV;
if (kobj->ktype && kobj->ktype->sysfs_ops)
//这里可谓是ktype实现中的核心,在这里ops设置成了platform_bus_type中kobject->ktype的sysfs_ops
ops = kobj->ktype->sysfs_ops;
else {
printk(KERN_ERR "missing sysfs attribute operations for ""kobject: %s\n", kobject_name(kobj));
WARN_ON(1);
goto err_out;
}
if (file->f_mode & FMODE_WRITE) {
if (!(inode->i_mode & S_IWUGO) || !ops->store)
goto err_out;
}
if (file->f_mode & FMODE_READ) {
if (!(inode->i_mode & S_IRUGO) || !ops->show)
goto err_out;
}
error = -ENOMEM;
buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL);
if (!buffer)
goto err_out;
mutex_init(&buffer->mutex);
buffer->needs_read_fill = 1;
//然后将设置好的ops挂载到buffer上
buffer->ops = ops;
//再将buffer挂载到file->private_data中
file->private_data = buffer;
error = sysfs_get_open_dirent(attr_sd, buffer);
if (error)
goto err_free;
sysfs_put_active_two(attr_sd);
return 0;
err_free:
kfree(buffer);
err_out:
sysfs_put_active_two(attr_sd);
return error;
}
现在已经为read和write操作准备好了
马上进入到read操作中
整个流程如上图所示,如何进入到sysfs_read_file在上面open的操作中已经说明了
我们就从sysfs_read_file开始分析(该文件在/fs/sysfs/file.c中)
sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
struct sysfs_buffer * buffer = file->private_data;
ssize_t retval = 0;
mutex_lock(&buffer->mutex);
if (buffer->needs_read_fill || *ppos == 0) {
//主要操作在fill_read_buffer中
retval = fill_read_buffer(file->f_path.dentry,buffer);
if (retval)
goto out;
}
pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n",__func__, count, *ppos, buffer->page);
retval = simple_read_from_buffer(buf, count, ppos, buffer->page,
buffer->count);
out:
mutex_unlock(&buffer->mutex);
return retval;
}
static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer)
{
struct sysfs_dirent *attr_sd = dentry->d_fsdata;
//取得父目录的kobject,也就是platform的kobject
struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
//还记得这个buffer->ops在什么时候进行赋值的么?
struct sysfs_ops * ops = buffer->ops;
int ret = 0;
ssize_t count;
if (!buffer->page)
buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
if (!buffer->page)
return -ENOMEM;
if (!sysfs_get_active_two(attr_sd))
return -ENODEV;
buffer->event = atomic_read(&attr_sd->s_attr.open->event);
//调用ops->show 也就是bus_sysfs_ops->show 具体就是bus_attr_show了
//参数为父目录的kobject, bus_attr_drivers_autoprobe->attr,和一段char信息
count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);
sysfs_put_active_two(attr_sd);
if (count >= (ssize_t)PAGE_SIZE) {
print_symbol("fill_read_buffer: %s returned bad count\n",
(unsigned long)ops->show);
/* Try to struggle along */
count = PAGE_SIZE - 1;
}
if (count >= 0) {
buffer->needs_read_fill = 0;
buffer->count = count;
} else {
ret = count;
}
return ret;
}
现在进入bus_attr_show中
static ssize_t bus_attr_show(struct kobject *kobj, struct attribute *attr,char *buf)
{
//提取attr的上层结构,也就是bus_attr_drivers_autoprobe
struct bus_attribute *bus_attr = to_bus_attr(attr);
//提取kobj的上上层结构,也就是bus_type_private
struct bus_type_private *bus_priv = to_bus(kobj);
ssize_t ret = 0;
if (bus_attr->show)
//终于到了这里,最后的调用,调用bus_attr_drivers_autoprobe.show ,也就是show_drivers_autoprobe
//参数为bus_priv->bus,也就是platform_bus_type , 及一段char信息
ret = bus_attr->show(bus_priv->bus, buf);
return ret;
}
static ssize_t show_drivers_autoprobe(struct bus_type *bus, char *buf)
{
return sprintf(buf, "%d\n", bus->p->drivers_autoprobe);
}
没什么好介绍了就是打印 buf + bus->p->drivers_autoprobe 从结果来看~ buf是空的
到这里,终于把内核的信息给打印出来了,千辛万苦,层层调用,就是为了取得上层kobject结构,逆运算再取得kobject的上层结构
大家是否对kobject有所了解了呢?~
在对kobject进行介绍之前 还是先把write操作讲完吧 哈哈~
write操作和read操作重要的步骤基本是一致的,只不过在最后的调用中
static ssize_t store_drivers_autoprobe(struct bus_type *bus,
const char *buf, size_t count)
{
if (buf[0] == '0')
bus->p->drivers_autoprobe = 0;
else
bus->p->drivers_autoprobe = 1;
return count;
}
不进行打印而对内核的参数进行了修改而已
好~ 现在让我们来看看kobject吧
kobject的结构如下
struct kobject {
const char *name; //kobject的名字
struct kref kref; //kobject的原子操作
struct list_head entry;
struct kobject *parent; //父对象
struct kset *kset; //父容器
struct kobj_type *ktype; //ktype
struct sysfs_dirent *sd; //文件节点
unsigned int state_initialized:1;
unsigned int state_in_sysfs:1;
unsigned int state_add_uevent_sent:1;
unsigned int state_remove_uevent_sent:1;
};
kobject描述的是较具体的对象,一个设备,一个驱动,一个总线,一类设备
在层次图上可以看出,每个存在于层次图中的设备,驱动,总线,类别都有自己的kobject
kobject与kobject之间的层次由kobject中的parent指针决定
而kset指针则表明了kobject的容器
像platform_bus 和test_device的kset都是devices_kset
呢parent和kset有什么不同呢
我认为是人工和默认的区别,看下面这张图 ,蓝框为kset,红框为kobject
容器提供了一种默认的层次~ 但也可以人工设置层次
对于kobject现在我只理解了这么多,欢迎大家指出有疑问的地方
最后是kset,kset比较简单,看下面的结构
struct kset {
struct list_head list;
spinlock_t list_lock;
struct kobject kobj;
struct kset_uevent_ops *uevent_ops;
};
对于kset的描述,文档里也有介绍
/**
* 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.
翻译过来大概就是
结构kset,一个指定类型的kobject的集合,属于某一个指定的子系统
kset定义了一组kobject,它们可以是不同类型组成但却希望捆在一起有一个统一的操作
kset通常被定义为回调属性和其他通用的事件发生在kobject上
可能翻译的不是很好,望大家见谅
从结构中能看出kset比kobject多了3个属性
list_head //列表
spinlock_t //共享锁
kset_uevent_ops //uevent操作集
list_head 连接了所有kobject中kset属性指向自己的kobject
而kset_uevent_ops则用于通知机制,由于uevent的作用我也没接触过,所以暂不解析uevent的机制了
