注册：函数调用
以音频设备注册为例，音频声卡初始化
代码目录：kernel/sound/soc/xxxx.c
static int __init audio_card_init(void)
{
int ret =0;
xxxx_snd_device = platform_device_alloc("soc-audio", -1);
if (!xxxx_snd_device) {
ret = -ENOMEM;
return ret;
}
platform_set_drvdata(xxxx_snd_device, &xxxx_snd_devdata);
xxxx_snd_devdata.dev = &xxxx_snd_device->dev;
ret = platform_device_add(xxxx_snd_device);
if (ret) {
platform_device_put(rk2818_snd_device);
}
return ret;
}
平台注册
代码目录:kernel/drivers/base/platform.c
/**
* platform_device_add - add a platform device to device hierarchy
* @pdev: platform device we're adding
*
* This is part 2 of platform_device_register(), though may be called
* separately _iff_ pdev was allocated by platform_device_alloc().
*/
int platform_device_add(struct platform_device *pdev)
{
int i, ret = 0;
if (!pdev)
return -EINVAL;
if (!pdev->dev.parent)
pdev->dev.parent = &platform_bus;
pdev->dev.bus = &platform_bus_type;
if (pdev->id != -1)
dev_set_name(&pdev->dev, "%s.%d", pdev->name,pdev->id);
else
dev_set_name(&pdev->dev, "%s", pdev->name);
for (i = 0; i < pdev->num_resources; i++) {
struct resource *p, *r = &pdev->resource[i];
if (r->name == NULL)
r->name = dev_name(&pdev->dev);
p = r->parent;
if (!p) {
if (resource_type(r) == IORESOURCE_MEM)
p = &iomem_resource;
else if (resource_type(r) == IORESOURCE_IO)
p = &ioport_resource;
}
if (p && insert_resource(p, r)) {
printk(KERN_ERR
"%s: failed to claim resource %d\n",
dev_name(&pdev->dev), i);
ret = -EBUSY;
goto failed;
}
}
pr_debug("Registering platform device '%s'. Parent at %s\n",
dev_name(&pdev->dev), dev_name(pdev->dev.parent));
ret = device_add(&pdev->dev);
if (ret == 0)
return ret;
failed:
while (--i >= 0) {
struct resource *r = &pdev->resource[i];
unsigned long type = resource_type(r);
if (type == IORESOURCE_MEM || type == IORESOURCE_IO)
release_resource(r);
}
return ret;
}
EXPORT_SYMBOL_GPL(platform_device_add);
设备添加
代码目录:kernel/drivers/base/core.c
/**
* device_add - add device to device hierarchy.
* @dev: device.
*
* This is part 2 of device_register(), though may be called
* separately _iff_ device_initialize() has been called separately.
*
* This adds @dev to the kobject hierarchy via kobject_add(), adds it
* to the global and sibling lists for the device, then
* adds it to the other relevant subsystems of the driver model.
*
* NOTE: _Never_ directly free @dev after calling this function, even
* if it returned an error! Always use put_device() to give up your
* reference instead.
*/
int device_add(struct device *dev)
{
struct device *parent = NULL;
struct class_interface *class_intf;
int error = -EINVAL;
dev = get_device(dev);
if (!dev)
goto done;
if (!dev->p) {
error = device_private_init(dev);
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);
dev->init_name = NULL;
}
if (!dev_name(dev))
goto name_error;
pr_debug("device: '%s': %s\n", dev_name(dev), __func__);
parent = get_device(dev->parent);
setup_parent(dev, 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);
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;
error = bus_add_device(dev);
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(dev);
if (parent)
klist_add_tail(&dev->p->knode_parent,
&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))
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;
}
设备添加到电源管理链表中
代码目录:kernel/drivers/base/main.c
/**
* device_pm_add - Add a device to the PM core's list of active devices.
* @dev: Device to add to the list.
*/
void device_pm_add(struct device *dev)
{
pr_debug("PM: Adding info for %s:%s\n",
dev->bus ? dev->bus->name : "No Bus",
kobject_name(&dev->kobj));
mutex_lock(&dpm_list_mtx);
if (dev->parent) {
if (dev->parent->power.status >= DPM_SUSPENDING)
dev_warn(dev, "parent %s should not be sleeping\n",
dev_name(dev->parent));
} else if (transition_started) {
/*
* We refuse to register parentless devices while a PM
* transition is in progress in order to avoid leaving them
* unhandled down the road
*/
dev_WARN(dev, "Parentless device registered during a PM transaction\n");
}
list_add_tail(&dev->power.entry, &dpm_list);
mutex_unlock(&dpm_list_mtx);
}
综上，设备挂到电源管理的函数调用关系是（依次往下调用）
audio_card_init （函数类型包含__init 初始化调用）
platform_device_add
device_add
device_pm_add
list_add_tail（最直接的链表添加操作）
应用：android休眠
1、state_store 调用 request_suspend_state，
2、然后request_suspend_state 调用early_suspend_work，完成一级休眠工作，
实际操作就是调用使用register_early_suspend注册的设备的suspend handle
比如触摸屏、按键、背光、重力感应等
3、early_suspend完成以后，
在函数末尾调用 wake_unlock(&main_wake_lock)，释放掉非超时锁main_wake_lock，
如果应用程序没有不释放的锁了，就会调用到二级睡眠入口函数suspend
4、suspend调用pm_suspend，再调用enter_state，
这里才是真正二级待机的入口了
5、在函数suspend_prepare完成冻结进程成功后，就到了关于非系统设备的suspend函数，
就是suspend_devices_and_enter
6、suspend_devices_and_enter进来以后先关掉控制器，
如果开发人员，此时就不能打出log了，为调试方便可以不关闭控制器；
dpm_suspend_start(PMSG_SUSPEND)就是和本文有关的函数入口了，
它要完成的工作是关闭所有（源代码是全部）非系统设备（non-sysdev），
里面的管理就是用到前面注册添加好的链表了
7、dpm_prepare和dpm_suspend类似，
只是前者是遍历链表置状态位标志status为prepare，调用设备的prepare函数；
后者是遍历链表置状态位标志status为suspend，调用设备的suspend函数
