這篇文章也是從別的地方轉載的，我的目的是搞清楚：當調用device_register()函數向系統註冊一個設備的時候，我註冊進去的設備是如何和他父設備關聯起來的，以及如何加入到他所在的總線設備中的，但針對這個問題，好像通過這篇文章瞭解的並不透徹。但具體到代碼分析的最後關於設備和驅動是如何綁定的，這並不是我這篇文章的重點，但大概看了一下，有點類型i2c總線上設備和驅動的匹配過程。
看下圖：
在分析程序的過程中看到了把kobj->kset賦值爲(kset)device_kset(即圖中黑線實現的部分),但沒有看到什麼時候把dev->kobj->parent賦值爲device_kset->kobj(圖中的紅線實現的部分)，在調用函數setup_parent()中是對dev->kobject->parent賦值了，但不明白在setup_parent()函數中是怎麼找到device_kset的。說實在話，對setup_parent()函數不明白，也沒分析清楚。（在此補充一下，分析了一下setup_parent()函數，實現了紅線的部分）
這篇文章將那個3個註冊函數說說，把整個設備模型框架搭建起來，當然，是重點部分了。在這之前希望你已經懂得總線、設備、驅動的數據結構及其裏面的有關數據結構。關於調用的函數，如果顯示爲粗體，那麼在下面我有分析。
轉載於：http://student.csdn.net/space.php?uid=111596&do=blog&id=56043
來自：drivers/base/core.c
int device_register(struct device *dev)
{
device_initialize(dev); //初始化設備
return device_add(dev); //添加設備
}
void device_initialize(struct device *dev)
{
//圖中的黑線實現部分的代碼
dev->kobj.kset = devices_kset; //設置設備的kobject所屬集合，devices_kset其實在第一層，sys/devices/
kobject_init(&dev->kobj, &device_ktype); //初始化設備的kobject
INIT_LIST_HEAD(&dev->dma_pools); //初始化設備的DMA池，用於傳遞大數據
mutex_init(&dev->mutex); //初始化互斥鎖
lockdep_set_novalidate_class(&dev->mutex);
spin_lock_init(&dev->devres_lock); //初始化自旋鎖，用於同步子設備鏈表
INIT_LIST_HEAD(&dev->devres_head); //初始化子設備鏈表頭
device_pm_init(dev);
set_dev_node(dev, -1);
}
int device_add(struct device *dev)
{
struct device *parent = NULL;
struct class_interface *class_intf;
int error = -EINVAL;
dev = get_device(dev); //增加設備的kobject的引用計數
if (!dev)
goto done;
if (!dev->p) {
error = device_private_init(dev); //初始化設備的私有成員
if (error)
goto done;
}
/*
* for statically allocated devices, which should all be converted
* some day, we need to initialize the name. We prevent reading back
* the name, and force the use of dev_name()
*/
if (dev->init_name) {
dev_set_name(dev, "%s", dev->init_name); //設置設備kobject的名稱
dev->init_name = NULL;
}
if (!dev_name(dev)) {
error = -EINVAL;
goto name_error;
}
pr_debug("device: '%s': %s/n", dev_name(dev), __func__);
parent = get_device(dev->parent); //增加父設備kobject的引用
setup_parent(dev, parent); //設置該設備kobject父對象（父對象是誰呢）
/* use parent numa_node */
if (parent)
set_dev_node(dev, dev_to_node(parent));
/* first, register with generic layer. */
/* we require the name to be set before, and pass NULL */
error = kobject_add(&dev->kobj, dev->kobj.parent, NULL); //將設備kobject添加進父對象設備模型
if (error)
goto Error;
/* notify platform of device entry */
if (platform_notify)
platform_notify(dev);
error = device_create_file(dev, &uevent_attr);
if (error)
goto attrError;
if (MAJOR(dev->devt)) {
error = device_create_file(dev, &devt_attr);
if (error)
goto ueventattrError;
error = device_create_sys_dev_entry(dev);
if (error)
goto devtattrError;
devtmpfs_create_node(dev);
}
error = device_add_class_symlinks(dev);
if (error)
goto SymlinkError;
error = device_add_attrs(dev);
if (error)
goto AttrsError;
調用bus_add_device在sysfs中添加兩個鏈接：一個在總線目錄下指向設備，另一個在設備的目錄下指向總線子系統。
error = bus_add_device(dev); //將設備添加進總線中
if (error)
goto BusError;
error = dpm_sysfs_add(dev);
if (error)
goto DPMError;
device_pm_add(dev);
/* Notify clients of device addition. This call must come
* after dpm_sysf_add() and before kobject_uevent().
*/
if (dev->bus)
blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
BUS_NOTIFY_ADD_DEVICE, dev);
kobject_uevent(&dev->kobj, KOBJ_ADD);
bus_probe_device試圖自動探測設備。如果能夠找到合適的驅動程序，則將設備添加到bus->klist_devices.設備還需要添加到父結點的子結點鏈表中，圖中藍色線的實現部分（此前，設備知道其父結點，但父結點不知道子結點的存在）
bus_probe_device(dev); //現在該爲設備在總線上尋找合適的驅動了
if (parent)
klist_add_tail(&dev->p->knode_parent,
&parent->p->klist_children); //將設備添加到父設備的子設備鏈表中
if (dev->class) {
mutex_lock(&dev->class->p->class_mutex);
/* tie the class to the device */
klist_add_tail(&dev->knode_class,
&dev->class->p->class_devices);
/* notify any interfaces that the device is here */
list_for_each_entry(class_intf,
&dev->class->p->class_interfaces, node)
if (class_intf->add_dev)
class_intf->add_dev(dev, class_intf);
mutex_unlock(&dev->class->p->class_mutex);
}
done:
put_device(dev);
return error;
DPMError:
bus_remove_device(dev);
BusError:
device_remove_attrs(dev);
AttrsError:
device_remove_class_symlinks(dev);
SymlinkError:
if (MAJOR(dev->devt))
devtmpfs_delete_node(dev);
if (MAJOR(dev->devt))
device_remove_sys_dev_entry(dev);
devtattrError:
if (MAJOR(dev->devt))
device_remove_file(dev, &devt_attr);
ueventattrError:
device_remove_file(dev, &uevent_attr);
attrError:
kobject_uevent(&dev->kobj, KOBJ_REMOVE);
kobject_del(&dev->kobj);
Error:
cleanup_device_parent(dev);
if (parent)
put_device(parent);
name_error:
kfree(dev->p);
dev->p = NULL;
goto done;
}
int device_private_init(struct device *dev)
{
dev->p = kzalloc(sizeof(*dev->p), GFP_KERNEL);
if (!dev->p)
return -ENOMEM;
dev->p->device = dev; //指向設備自己
klist_init(&dev->p->klist_children, klist_children_get,
klist_children_put); //初始化設備私有成員的子設備鏈表，還有兩個函數，關於增加和減少子設備引用計數的
return 0;
}
static void setup_parent(struct device *dev, struct device *parent)
{
struct kobject *kobj;
kobj = get_device_parent(dev, parent); //得到設備kobject的父對象
if (kobj)
dev->kobj.parent = kobj;
}
int bus_add_device(struct device *dev)
{
struct bus_type *bus = bus_get(dev->bus);
int error = 0;
if (bus) {
pr_debug("bus: '%s': add device %s/n", bus->name, dev_name(dev));
error = device_add_attrs(bus, dev);
if (error)
goto out_put;
error = sysfs_create_link(&bus->p->devices_kset->kobj,
&dev->kobj, dev_name(dev));
if (error)
goto out_id;
error = sysfs_create_link(&dev->kobj,
&dev->bus->p->subsys.kobj, "subsystem");
if (error)
goto out_subsys;
error = make_deprecated_bus_links(dev);
if (error)
goto out_deprecated;
klist_add_tail(&dev->p->knode_bus, &bus->p->klist_devices); //關鍵點了，將設備添加進總線的設備鏈表
}
return 0;
out_deprecated:
sysfs_remove_link(&dev->kobj, "subsystem");
out_subsys:
sysfs_remove_link(&bus->p->devices_kset->kobj, dev_name(dev));
out_id:
device_remove_attrs(bus, dev);
out_put:
bus_put(dev->bus);
return error;
}
void bus_probe_device(struct device *dev)
{
struct bus_type *bus = dev->bus;
int ret;
if (bus && bus->p->drivers_autoprobe) { //如果需要自動匹配驅動
ret = device_attach(dev); //爲設備尋找驅動
WARN_ON(ret < 0);
}
}
int device_attach(struct device *dev)
{
int ret = 0;
device_lock(dev); //鎖住設備
if (dev->driver) { //如果設備有驅動
ret = device_bind_driver(dev); //那麼將設備和驅動綁定
if (ret == 0)
ret = 1;
else {
dev->driver = NULL;
ret = 0;
}
} else {
pm_runtime_get_noresume(dev);
ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach); //否則，在總線上尋找驅動與該設備進行匹配
pm_runtime_put_sync(dev);
}
device_unlock(dev);
return ret;
}
int device_bind_driver(struct device *dev)
{
int ret;
ret = driver_sysfs_add(dev);
if (!ret)
driver_bound(dev); //驅動綁定設備
return ret;
}
int bus_for_each_drv(struct bus_type *bus, struct device_driver *start,
void *data, int (*fn)(struct device_driver *, void *))
{
struct klist_iter i;
struct device_driver *drv;
int error = 0;
if (!bus)
return -EINVAL;
klist_iter_init_node(&bus->p->klist_drivers, &i,
start ? &start->p->knode_bus : NULL); //初始化i結構體
while ((drv = next_driver(&i)) && !error) //遍歷總線上的驅動
error = fn(drv, data); //將驅動和設備進行匹配，這裏的fn=__device_attach
klist_iter_exit(&i);
return error;
}
static int __device_attach(struct device_driver *drv, void *data)
{
struct device *dev = data;
if (!driver_match_device(drv, dev)) //現用總線上的match匹配函數進行低級匹配
return 0;
return driver_probe_device(drv, dev); //在來高級匹配
}
static inline int driver_match_device(struct device_driver *drv, struct device *dev)
{
return drv->bus->match ? drv->bus->match(dev, drv) : 1; //看到沒，這裏要調用總線上定義的match函數
}
int driver_probe_device(struct device_driver *drv, struct device *dev)
{
int ret = 0;
if (!device_is_registered(dev)) //設備是否註冊
return -ENODEV;
pr_debug("bus: '%s': %s: matched device %s with driver %s/n",
drv->bus->name, __func__, dev_name(dev), drv->name);
pm_runtime_get_noresume(dev);
pm_runtime_barrier(dev);
ret = really_probe(dev, drv); //調用真正的匹配
pm_runtime_put_sync(dev);
return ret;
}
static int really_probe(struct device *dev, struct device_driver *drv)
{
int ret = 0;
atomic_inc(&probe_count);
pr_debug("bus: '%s': %s: probing driver %s with device %s/n",
drv->bus->name, __func__, drv->name, dev_name(dev));
WARN_ON(!list_empty(&dev->devres_head));
dev->driver = drv;
if (driver_sysfs_add(dev)) {
printk(KERN_ERR "%s: driver_sysfs_add(%s) failed/n",
__func__, dev_name(dev));
goto probe_failed;
}
if (dev->bus->probe) { //現用總線上定義的probe函數嘗試一下
ret = dev->bus->probe(dev);
if (ret)
goto probe_failed;
} else if (drv->probe) { //如果不行，在用驅動上的probe嘗試
ret = drv->probe(dev);
if (ret)
goto probe_failed;
}
driver_bound(dev); //驅動綁定設備
ret = 1;
pr_debug("bus: '%s': %s: bound device %s to driver %s/n",
drv->bus->name, __func__, dev_name(dev), drv->name);
goto done;
probe_failed:
devres_release_all(dev);
driver_sysfs_remove(dev);
dev->driver = NULL;
if (ret != -ENODEV && ret != -ENXIO) {
/* driver matched but the probe failed */
printk(KERN_WARNING
"%s: probe of %s failed with error %d/n",
drv->name, dev_name(dev), ret);
}
/*
* Ignore errors returned by ->probe so that the next driver can try
* its luck.
*/
ret = 0;
done:
atomic_dec(&probe_count);
wake_up(&probe_waitqueue);
return ret;
}