出处：http://blog.csdn.net/coolraining/article/details/6678759
新版linux系统设备架构中关于电源管理方式的变更based on linux-2.6.32
一、设备模型各数据结构中电源管理的部分
linux的设备模型通过诸多结构体来联合描述，如struct device，struct device_type，struct class，struct device_driver，struct bus_type等。@kernel/include/linux/devices.h中有这几中结构体的定义，这里只列出和PM有关的项，其余查看源码：struct device{…struct dev_pm_infopower; …}struct device_type {…int (*uevent)(struct device *dev, struct kobj_uevent_env *env);char *(*devnode)(struct device *dev, mode_t *mode);void (*release)(struct device *dev);const struct dev_pm_ops *pm;};struct class {…void (*class_release)(struct class *class);void (*dev_release)(struct device *dev);int (*suspend)(struct device *dev, pm_message_t state);int (*resume)(struct device *dev);const struct dev_pm_ops *pm;…};struct device_driver {…int (*probe) (struct device *dev);int (*remove) (struct device *dev);void (*shutdown) (struct device *dev);int (*suspend) (struct device *dev, pm_message_t state);int (*resume) (struct device *dev);const struct dev_pm_ops *pm;…};struct bus_type {…int (*match)(struct device *dev, struct device_driver *drv);int (*uevent)(struct device *dev, struct kobj_uevent_env *env);int (*probe)(struct device *dev);int (*remove)(struct device *dev);void (*shutdown)(struct device *dev);int (*suspend)(struct device *dev, pm_message_t state);int (*resume)(struct device *dev);
const struct dev_pm_ops *pm;…};以上可以看出和电源管理相关的两个结构体是struct dev_pm_info和struct dev_pm_ops，他们定义于文件@kernel/include/linux/pm.hstruct dev_pm_info {pm_message_tpower_state;unsigned intcan_wakeup:1;unsigned intshould_wakeup:1;enum dpm_statestatus;/* Owned by the PM core – 表示该设备当前的PM状态*/#ifdef CONFIG_PM_SLEEPstruct list_headentry;/* 链接到dpm_list全局链表中的连接体 */#endif#ifdef CONFIG_PM_RUNTIME// undefstruct timer_listsuspend_timer;unsigned longtimer_expires;struct work_structwork;wait_queue_head_twait_queue;spinlock_tlock;atomic_tusage_count;atomic_tchild_count;unsigned intdisable_depth:3;unsigned intignore_children:1;unsigned intidle_notification:1;unsigned intrequest_pending:1;unsigned intdeferred_resume:1;enum rpm_requestrequest;enum rpm_statusruntime_status;intruntime_error;#endif};struct dev_pm_ops {int (*prepare)(struct device *dev);void (*complete)(struct device *dev);int (*suspend)(struct device *dev);int (*resume)(struct device *dev);int (*freeze)(struct device *dev);int (*thaw)(struct device *dev);int (*poweroff)(struct device *dev);int (*restore)(struct device *dev);int (*suspend_noirq)(struct device *dev);int (*resume_noirq)(struct device *dev);int (*freeze_noirq)(struct device *dev);int (*thaw_noirq)(struct device *dev);int (*poweroff_noirq)(struct device *dev);int (*restore_noirq)(struct device *dev);int (*runtime_suspend)(struct device *dev);int (*runtime_resume)(struct device *dev);int (*runtime_idle)(struct device *dev);};
二、device中的dev_pm_info结构体
device结构体中的power项用来将该设备纳入电源管理的范围，记录电源管理的一些信息。在注册设备的时候调用函数device_add()来向sysfs系统添加power接口和注册进电源管理系统，代码片段如下：…error = dpm_sysfs_add(dev);@kernel/drivers/base/power/sysfs.cif (error)goto DPMError;device_pm_add(dev);@kernel/drivers/base/power/main.c…其中dpm_sysfs_add()函数用来向sysfs文件系统中添加相应设备的power接口文件，如注册mt6516_tpd paltform device的时候，会在sysfs中出现如下目录和文件：#pwd/sys/devices/platform/mt6516-tpd#cd mt6516-tpd#ls -l-rw-r–r– root root 4096 2010-01-02 06:35 uevent-r–r–r– root root 4096 2010-01-02 06:39 modaliaslrwxrwxrwx root root 2010-01-02 06:39 subsystem -> ../../../bus/platformdrwxr-xr-x root root 2010-01-02 06:35 powerlrwxrwxrwx root root 2010-01-02 06:39 driver -> ../../../bus/platform/drivers/mt6516-tpd#cd power#ls -l-rw-r–r– root root 4096 2010-01-02 06:39 wakeup源码片段：static DEVICE_ATTR(wakeup, 0644, wake_show, wake_store);
static struct attribute * power_attrs[] = {&dev_attr_wakeup.attr,NULL,};static struct attribute_group pm_attr_group = {.name= "power",// attribute_group结构体的name域不为NULL的话，都会已name建立一个属性目录的.attrs= power_attrs,};int dpm_sysfs_add(struct device * dev){return sysfs_create_group(&dev->kobj, &pm_attr_group);//在当前device的kobject结构体对应的目录下建立}其中的device_pm_add()函数会将该设备插入到电源管理的核心链表dpm_list中统一管理。值得一提的是，在函数device_initialize()会调用函数device_pm_init()来初始化该device结构体的power域：dev->power.status = DPM_ON;void device_pm_add(struct device *dev){…mutex_lock(&dpm_list_mtx);if (dev->parent) {if (dev->parent->power.status >= DPM_SUSPENDING) // 如果某设备处于DPM_SUSPENDING极其之后的状态，此时不允许以该设备为父设备注册子设备dev_warn(dev, "parent %s should not be sleeping/n", dev_name(dev->parent));} else if (transition_started) { // transition_started全局变量包含在PM transition期间不允许注册设备/* * 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);// 将device结构体通过power.entry项链接进dpm_listmutex_unlock(&dpm_list_mtx);}void device_pm_remove(struct device *dev){…mutex_lock(&dpm_list_mtx);list_del_init(&dev->power.entry);mutex_unlock(&dpm_list_mtx);pm_runtime_remove(dev);}
举例说明：我们熟知的platform bus在系统中也是作为一种设备注册进了系统，在sysfs文件系统中的位置是：/sys/devices/platform。使用函数device_register(&platform_bus)进行注册，调用device_add()函数，注册ok之后，也会出现目录/sys/devices/platform/power。最后也会将其添加进dpm_list中。i2c控制器外设代表的设备是注册在platform总线上的，也就是说它的父设备是platform。最终在platform_device_add()中会调用函数device_add()函数来添加设备，最终也会在mt6516-i2c.0/mt6516-i2c.1/mt6516-i2c.2中出现一个power目录，同时这3个platform设备会依靠platform_device.dev.power.entry连接件链接到电源管理核心链表dpm_list中。/sys/devices/platform/mt6516-i2c.2/power每一个i2c控制器都会在系统中至少注册成一个适配器(adapter),该结构体将会间接提供给i2c设备的驱动来使用，以避免直接使用i2c控制器结构体。这个适配器没有对应的driver，在错综复杂的i2c架构中，相对于只起到了一个承上启下的作用，上接i2c控制器的结构体及driver，下接i2c设备的结构体i2c_client和特点的driver。adapter.dev.parent为i2c控制器对应的device，所以就会出现名为i2c-0/1/2的设备kobject，只是该设备的bus总线和device_type是：adap->dev.bus = &i2c_bus_type;adap->dev.type = &i2c_adapter_type;然后调用函数device_register(&adap->dev);来注册这个device，所以在对应的i2c-0/1/2目录下也会出现power目录。/sys/devices/platform/mt6516-i2c.2/i2c-2/poweri2c设备会通过自动检测或者事先静态描述的方式来注册进系统，不管什么方式，都会调用到函数：i2c_new_device()struct i2c_client*client;client->dev.parent = &client->adapter->dev;client->dev.bus = &i2c_bus_type;client->dev.type = &i2c_client_type;dev_set_name(&client->dev, "%d-%04x", i2c_adapter_id(adap), client->addr);status = device_register(&client->dev);可以看得出来名字是什么了，例如：2-00aa#ls -l /sys/devices/platform/mt6516-i2c.2/i2c-2/2-00aa-rw-r–r– root root 4096 2010-01-02 06:35 uevent-r–r–r– root root 4096 2010-01-02 06:38 name-r–r–r– root root 4096 2010-01-02 06:38 modaliaslrwxrwxrwx root root 2010-01-02 06:38 subsystem -> ../../../../../bus/i2cdrwxr-xr-x root root 2010-01-02 06:35 powerlrwxrwxrwx root root 2010-01-02 06:38 driver -> ../../../../../bus/i2c/drivers/mt6516-tpd
三、bus_type、device_driver、device_type、class中的dev_pm_ops方法结构体在新的linux内核中，已不再有subsystem数据结构了，他的功能被kset代替。全局变量bus_kset初始化：kernel_init()–>do_basic_setup()–>driver_init()–>buses_init()bus_kset = kset_create_and_add("bus", &bus_uevent_ops, NULL);1. 总线类型结构体：bus_type，以platform和i2c总线为例：@kernel/drivers/base/platform.cstatic const struct dev_pm_ops platform_dev_pm_ops = {.prepare = platform_pm_prepare,// .complete = platform_pm_complete,//.suspend = platform_pm_suspend,//.resume = platform_pm_resume,//.freeze = platform_pm_freeze,.thaw = platform_pm_thaw,.poweroff = platform_pm_poweroff,//.restore = platform_pm_restore,.suspend_noirq = platform_pm_suspend_noirq,.resume_noirq = platform_pm_resume_noirq,.freeze_noirq = platform_pm_freeze_noirq,.thaw_noirq = platform_pm_thaw_noirq,.poweroff_noirq = platform_pm_poweroff_noirq,.restore_noirq = platform_pm_restore_noirq,.runtime_suspend = platform_pm_runtime_suspend,.runtime_resume = platform_pm_runtime_resume,.runtime_idle = platform_pm_runtime_idle,};struct bus_type platform_bus_type = {.name= "platform",.dev_attrs= platform_dev_attrs,.match= platform_match,.uevent= platform_uevent,.pm= &platform_dev_pm_ops,};从上面的dev_pm_ops结构体中拿出最普遍使用的函数指针来说明一下，对于bus_type它的电源管理是如何实现的。static int platform_pm_prepare(struct device *dev){struct device_driver *drv = dev->driver;int ret = 0;if (drv && drv->pm && drv->pm->prepare)ret = drv->pm->prepare(dev);return ret;}static void platform_pm_complete(struct device *dev){struct device_driver *drv = dev->driver;if (drv && drv->pm && drv->pm->complete)drv->pm->complete(dev);}可以看出这两个函数都最终是利用了device_driver结构体中的dev_pm_ops函数方法结构体中的对应函数指针。////////////////////////////////////////////static int platform_legacy_suspend(struct device *dev, pm_message_t mesg){struct platform_driver *pdrv = to_platform_driver(dev->driver);struct platform_device *pdev = to_platform_device(dev);int ret = 0;if (dev->driver && pdrv->suspend)ret = pdrv->suspend(pdev, mesg);return ret;}static int platform_legacy_resume(struct device *dev){struct platform_driver *pdrv = to_platform_driver(dev->driver);struct platform_device *pdev = to_platform_device(dev);int ret = 0;if (dev->driver && pdrv->resume)ret = pdrv->resume(pdev);return ret;}////////////////////////////////////////////static int platform_pm_suspend(struct device *dev){struct device_driver *drv = dev->driver;int ret = 0;if (!drv)return 0;if (drv->pm) {if (drv->pm->suspend)ret = drv->pm->suspend(dev);} else {ret = platform_legacy_suspend(dev, PMSG_SUSPEND);}return ret;}static int platform_pm_resume(struct device *dev){struct device_driver *drv = dev->driver;int ret = 0;if (!drv)return 0;if (drv->pm) {if (drv->pm->resume)ret = drv->pm->resume(dev);} else {ret = platform_legacy_resume(dev);}return ret;}
这里suspend和resume函数也是最终都是调用了device_driver结构体的dev_pm_ops方法结构体中的对应函数指针(device_driver.pm项被初始化)，否则使用老式的方法：platform_legacy_suspend(dev, PMSG_SUSPEND)和platform_legacy_resume(dev)。根据这两个函数的源码可以看出。一般地，在我们的platform device的platform driver定义中，都是实现了pdrv.suspend和pdrv.resume函数，而并没有实现pdrv.driver.suspend和pdrv.driver.resume函数，其余三个函数可以在platform_driver_register()函数中看出：int platform_driver_register(struct platform_driver *drv){drv->driver.bus = &platform_bus_type;if (drv->probe)drv->driver.probe = platform_drv_probe;if (drv->remove)drv->driver.remove = platform_drv_remove;if (drv->shutdown)drv->driver.shutdown = platform_drv_shutdown;return driver_register(&drv->driver);}i2c总线注册没有使用新式的电源管理方法：dev_pm_ops，仍然使用老式的方式：@kernel/drivers/i2c/i2c-core.cstruct bus_type i2c_bus_type = {.name= "i2c",.match= i2c_device_match,.probe= i2c_device_probe,.remove= i2c_device_remove,.shutdown= i2c_device_shutdown,.suspend= i2c_device_suspend,.resume= i2c_device_resume,};static int i2c_device_suspend(struct device *dev, pm_message_t mesg){struct i2c_client *client = i2c_verify_client(dev);struct i2c_driver *driver;if (!client || !dev->driver)return 0;driver = to_i2c_driver(dev->driver);if (!driver->suspend)return 0;return driver->suspend(client, mesg);}static int i2c_device_resume(struct device *dev){struct i2c_client *client = i2c_verify_client(dev);struct i2c_driver *driver;if (!client || !dev->driver)return 0;driver = to_i2c_driver(dev->driver);if (!driver->resume)return 0;return driver->resume(client);}// 实际上都是调用的i2c_driver结构体的suspend和resume函数。2. device_type结构体暂时还没有找到有哪一个模块使用了新式了dev_pm_ops电源管理方法，一般都是没有实现这部分。3. class结构体也没有找到使用dev_pm_ops方法结构体的地方，先暂时放一放。4. device_driver struct device_driver {const char*name;struct bus_type*bus;…int (*probe) (struct device *dev);int (*remove) (struct device *dev);void (*shutdown) (struct device *dev);int (*suspend) (struct device *dev, pm_message_t state);int (*resume) (struct device *dev);const struct attribute_group **groups;const struct dev_pm_ops *pm;struct driver_private *p;};struct i2c_driver {…/* driver model interfaces that don’t relate to enumeration */void (*shutdown)(struct i2c_client *);int (*suspend)(struct i2c_client *, pm_message_t mesg);int (*resume)(struct i2c_client *);…struct device_driver driver;const struct i2c_device_id *id_table;/* Device detection callback for automatic device creation */int (*detect)(struct i2c_client *, int kind, struct i2c_board_info *);const struct i2c_client_address_data *address_data;struct list_head clients;};一般都是实现了platform driver和i2c_driver结构体的suspend和resume函数,并没有使用新式的电源管理方式。
享受每一刻的感觉，欣赏每一处的风景，这就是人生。
