linux设备驱动模型一上层容器之device
系统中任一设备都有一个device对象描述,我们先来看一下它在内核中的表示：
struct device {
struct device *parent;//父设备
struct device_private *p;//设备的私有数据
struct kobject kobj;//表示该设备并把它链接到设备模型中的kobject
const char *init_name;//初始化名字
struct device_type *type;//设备的类型
struct mutex mutex; //用于互斥访问
struct bus_type *bus; // 标识了该设备链接在哪一个总线上
struct device_driver *driver; // 管理该设备的驱动程序，一个设备只能有一个驱动程序
void *platform_data; //平台的特定数据
struct dev_pm_info power;
#ifdef CONFIG_NUMA
int numa_node; /* NUMA node this device is close to */
#endif
u64 *dma_mask; //指向设备DMA屏蔽字
u64 coherent_dma_mask;//设备一致性DMA的屏蔽字
struct device_dma_parameters *dma_parms;
struct list_head dma_pools; //聚集的DMA缓冲池
struct dma_coherent_mem *dma_mem; //指向设备所使用的一致性DMA存储器描述符的指针
struct dev_archdata archdata;
#ifdef CONFIG_OF
struct device_node *of_node;
#endif
dev_t devt; /* dev_t, creates the sysfs "dev" */
spinlock_t devres_lock;//用于互斥访问设备
struct list_head devres_head;
struct klist_node knode_class;
struct class *class;//指向属于的类
const struct attribute_group **groups; /* optional groups */
void (*release)(struct device *dev);//释放设备描述符的回调函数
};
struct device_private {
struct klist klist_children;//该设备的子设备链表
struct klist_node knode_parent;//此结点将device链入device的parent的children链表
struct klist_node knode_driver;//此结点将device链入device对应的driver的devices链表
struct klist_node knode_bus;//此结点将device链入到对应的bus的devices链表
void *driver_data;//设备驱动程序使用的私有数据
struct device *device;//指向与之相关的device
};
可以看到 device_private 的作用主要是把device链接入n个链表，以方便查找设备。
有关device，最重要的一个函数就是device_register,它的作用主要是注册设备驱动程序，搜寻驱动drv对应的设备，并与之关联。
int device_register(struct device *dev)
{
device_initialize(dev);//初始化dev
return device_add(dev); //添加dev
}这个函数比较简单，主要是调用另外两个函数进行设备的初始化和添加操作，首先看下device_initialize
void device_initialize(struct device *dev)
{
dev->kobj.kset = devices_kset;//设置设备的kobject所属集合，devices_kset其实在第一层，sys/devices/
kobject_init(&dev->kobj, &device_ktype); //初始化设备的kobject
INIT_LIST_HEAD(&dev->dma_pools); //初始化设备的DMA池，用于传递大数据
mutex_init(&dev->mutex); //初始化互斥锁
lockdep_set_novalidate_class(&dev->mutex);
spin_lock_init(&dev->devres_lock);//初始化自旋锁，用于同步子设备链表
INIT_LIST_HEAD(&dev->devres_head); //初始化子设备链表头
device_pm_init(dev);// 此函数初始化device的power域
set_dev_node(dev, -1);
}devices_kset是所有dev的kset，也就是所有dev都被链接在该kset下，这个kset是在设备初始化的时候创建的
int __init devices_init(void)
{
devices_kset = kset_create_and_add("devices", &device_uevent_ops, NULL);
......
char_kobj_err:
kobject_put(sysfs_dev_block_kobj);
block_kobj_err:
kobject_put(dev_kobj);
dev_kobj_err:
kset_unregister(devices_kset);
return -ENOMEM;
}
parent=NULL,所以生成/sys/devices目录
void device_initialize(struct device *dev)
{
dev->kobj.kset = devices_kset;//设置设备的kobject所属集合，devices_kset其实在第一层，sys/devices/
kobject_init(&dev->kobj, &device_ktype); //初始化设备的kobject
INIT_LIST_HEAD(&dev->dma_pools); //初始化设备的DMA池，用于传递大数据
mutex_init(&dev->mutex); //初始化互斥锁
lockdep_set_novalidate_class(&dev->mutex);
spin_lock_init(&dev->devres_lock);//初始化自旋锁，用于同步子设备链表
INIT_LIST_HEAD(&dev->devres_head); //初始化子设备链表头
device_pm_init(dev);// 此函数初始化device的power域
set_dev_node(dev, -1);
}device_initialize对设备结构进行初始化，这里的ktype是device_ktype,kset是devices_kset
接着调用device_add添加到驱动模型中去。
int device_add(struct device *dev)
{
struct device *parent = NULL;
struct class_interface *class_intf;
int error = -EINVAL;
dev = get_device(dev);//增加设备的kobject的引用计数
if (!dev)
goto done;
if (!dev->p) {
error = device_private_init(dev);//初始化dev的私有成员，及其链表操作函数
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) { //保存设备名，以后需要获取时使用dev_name函数获取
dev_set_name(dev, "%s", dev->init_name);
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);//返回父节点，增加父节点引用计数，如果有返回，没有返回NULL
setup_parent(dev, parent);//以上层devices为准重设dev->kobj.parent
/* 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); //设置dev->kobj的名字和父对象,并建立相应目录
if (error)
goto Error;
/* notify platform of device entry */
if (platform_notify)
platform_notify(dev);
error = device_create_file(dev, &uevent_attr); //建立uevent属性文件
if (error)
goto attrError;
if (MAJOR(dev->devt)) {
error = device_create_file(dev, &devt_attr);//在sys下产生dev属性文件
if (error)
goto ueventattrError;
error = device_create_sys_dev_entry(dev);
if (error)
goto devtattrError;
devtmpfs_create_node(dev);
}
//建立subsystem链接文件连接到所属class
error = device_add_class_symlinks(dev);
if (error)
goto SymlinkError;
//添加dev的属性描述文件
error = device_add_attrs(dev);
if (error)
goto AttrsError;
error = bus_add_device(dev); //添加链接文件至所属bus
if (error)
goto BusError;
error = dpm_sysfs_add(dev); //添加power文件
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);//向用户空间发出KOBJ_ADD 事件
bus_probe_device(dev);//检测驱动中有无适合的设备进行匹配,现在只添加了设备,还没有加载驱动,所以不会进行匹配
if (parent)
klist_add_tail(&dev->p->knode_parent, //把该设备的节点挂到其父节点的链表
&parent->p->klist_children);
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;
}这里看一下设备匹配：
void bus_probe_device(struct device *dev)//匹配driver以及初始化过程
{
struct bus_type *bus = dev->bus;
int ret;
if (bus && bus->p->drivers_autoprobe) {//设置了自动匹配初始化那么就开始匹配
ret = device_attach(dev);
WARN_ON(ret < 0);
}
}device_attach进行匹配操作。
int device_attach(struct device *dev)
{
int ret = 0;
device_lock(dev);
if (dev->driver) {//默认指定了driver就直接绑定
ret = device_bind_driver(dev);
if (ret == 0)
ret = 1;
else {
dev->driver = NULL;
ret = 0;
}
} else {//没有指定就进行遍历匹配
pm_runtime_get_noresume(dev);
ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach);
pm_runtime_put_sync(dev);
}
device_unlock(dev);
return ret;
}device_bind_driver进行驱动的绑定。
int device_bind_driver(struct device *dev)
{
int ret;
//将driver和dev使用link,链接到一起,使他们真正相关
ret = driver_sysfs_add(dev);
if (!ret)
driver_bound(dev);//将私有成员的driver节点挂到了driver的设备链表
return ret;
}
driver_sysfs_add建立软链，它会在驱动目录下建立一个到设备的同名链接，并且在设备目录下建立一个名为 driver.到驱动的链接
static int driver_sysfs_add(struct device *dev)
{
int ret;
ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,//驱动目录下dev->kobj目录链接到dev->kobj
kobject_name(&dev->kobj));
if (ret == 0) {
ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,//在dev->kobj目录下的driver目录链接到其驱动目录
"driver");
if (ret)
sysfs_remove_link(&dev->driver->p->kobj,
kobject_name(&dev->kobj));
}
return ret;
}
driver_bound将私有成员的driver节点挂到了driver的设备链表
static void driver_bound(struct device *dev)
{
if (klist_node_attached(&dev->p->knode_driver)) {//判断是否已经绑定
printk(KERN_WARNING "%s: device %s already bound\n",
__func__, kobject_name(&dev->kobj));
return;
}
pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev),
__func__, dev->driver->name);
klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices); //将设备添加到driver的链表
if (dev->bus)
blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
BUS_NOTIFY_BOUND_DRIVER, dev);//通知bus上所有设备bound消息
}回到device_attach，如果没有指定就进行遍历匹配
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,//和driver遍历device类似，从头开始遍历bus的driver链表
start ? &start->p->knode_bus : NULL); //发现一个driver就调用fn即__device_attach进行匹配
while ((drv = next_driver(&i)) && !error)
error = fn(drv, data);
klist_iter_exit(&i);
return error;
}再来看下__device_attach
static int __device_attach(struct device_driver *drv, void *data)
{
struct device *dev = data;
if (!driver_match_device(drv, dev))//匹配条件检查
return 0;
return driver_probe_device(drv, dev);//进行真正的匹配操作
}看下driver_match_device
static inline int driver_match_device(struct device_driver *drv,
struct device *dev)//bus的match存在就用bus的否则就直接匹配成功.match通常实现为首先扫描driver支持的id设备表，如果为NULL就用名字进行匹配
{
return drv->bus->match ? drv->bus->match(dev, drv) : 1;
}再来看下driver_probe_device，进行匹配操作
int driver_probe_device(struct device_driver *drv, struct device *dev)
{
int ret = 0;
if (!device_is_registered(dev))//判断该设备是否已经注册
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);//调用really_probe
pm_runtime_put_sync(dev);
return ret;
}
首先调用查看是否已经注册：
static inline int device_is_registered(struct device *dev)
{
return dev->kobj.state_in_sysfs; //在sysfs中表示已经注册
}
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; //device的driver初始化成该driver
if (driver_sysfs_add(dev)) {//驱动目录下建立一个到设备的同名链接，并且在设备目录下建立一个名为 driver.到驱动的链接
printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
__func__, dev_name(dev));
goto probe_failed;
}
if (dev->bus->probe) { //利用probe初始化设备
ret = dev->bus->probe(dev); //如果bus的probe存在就用bus的，
if (ret)
goto probe_failed;
} else if (drv->probe) {//如果bus的不存在driver的存在
ret = drv->probe(dev);//再用driver的
if (ret)
goto probe_failed;
}
driver_bound(dev);//调用driver_bound进行绑定
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;
}
再看下driver_bound
static void driver_bound(struct device *dev)
{
if (klist_node_attached(&dev->p->knode_driver)) {//判断是否已经绑定
printk(KERN_WARNING "%s: device %s already bound\n",
__func__, kobject_name(&dev->kobj));
return;
}
pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev),
__func__, dev->driver->name);
klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices); //将设备添加到driver的链表
if (dev->bus)
blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
BUS_NOTIFY_BOUND_DRIVER, dev);//通知bus上所有设备bound消息
}
到这里，设备就已经匹配成功了，这样就把设备和相应的驱动挂钩上了。
最后看一下他们的关系图：