[Android/Linux]-1.power_supply框架初识

前言：

 本着好奇的心态，power_supply是如何将battery，ac，usb等的相关信息参数送到framework层以及应用层的，
所以了解了一下power_supply的大概。

引用：

在别的博客说得比较好的一问一答，借用一下：问：安卓是怎么知道当前充电状态的，以及电池电量变化的？
答：是由底层（驱动层）主动通过uevent机制（实质是net_link方式的socket）（广泛应用于hotplug），充电插入与断开时，内核通过发送uevent信息，告诉android。
问：android如何知道各种参数并更新的？
答：通过kobject_uevent发送通知给上层，上层读取sys相关文件属性

安卓power_supply的大体框架图：
(后面补充)

power_supply驱动层代码分析：
1.power_supply的驱动层核心代码有以下几个个：

dir://kernel/drivers/power/Makefilepower_supply-y                := power_supply_core.o
//power_supply的核心代码，提供power_supply的注册接口power_supply-$(CONFIG_SYSFS)      += power_supply_sysfs.o
//power_supply的文件系统，也就是需要用户层，会通过这些文件节点来获取信息power_supply-$(CONFIG_LEDS_TRIGGERS)   += power_supply_leds.o
//power_supply的led trigger ，在不同的状态触发不同的trgger evnetobj-$(CONFIG_POWER_SUPPLY)    += power_supply.o

2.注册一个power_supply实例，大概需要做几件事情呢？

参考：展讯平台的sprd_battery.c
对power_supply_decs 和power_supply_cfg两个结构体进行填充,然后注册就完事了
......struct power_supply *ret_ptr = NULL;struct power_supply_desc *battery_desc = NULL,*ac_desc = NULL, *usb_desc = NULL;struct power_supply_config battery_cfg = {}, ac_cfg = {}, usb_cfg = {};
.....//填充 power_supply_desc结构体
......
//batterybattery_desc = devm_kzalloc(&pdev->dev,sizeof(struct power_supply_desc), GFP_KERNEL);if (battery_desc == NULL) {ret = -ENOMEM;goto err_desc_alloc_failed;}battery_desc->properties = sprdbat_battery_props;battery_desc->num_properties = ARRAY_SIZE(sprdbat_battery_props);battery_desc->get_property = sprdbat_battery_get_property;battery_desc->set_property = sprdbat_battery_set_property;battery_desc->property_is_writeable =sprdbat_battery_property_is_writeable;battery_desc->name = "battery";battery_desc->type = POWER_SUPPLY_TYPE_BATTERY;battery_desc->no_thermal = true;battery_cfg.drv_data = sprdbat_data;
//ac
ac_desc = devm_kzalloc(&pdev->dev,sizeof(struct power_supply_desc), GFP_KERNEL);if (ac_desc == NULL) {ret = -ENOMEM;goto err_desc_alloc_failed;}ac_desc->properties = sprdbat_ac_props;ac_desc->num_properties = ARRAY_SIZE(sprdbat_ac_props);ac_desc->get_property = sprdbat_ac_get_property;ac_desc->set_property = sprdbat_ac_set_property;ac_desc->property_is_writeable =sprdbat_ac_property_is_writeable;ac_desc->name = "ac";ac_desc->type = POWER_SUPPLY_TYPE_MAINS;ac_desc->no_thermal = true;ac_cfg.drv_data = sprdbat_data;//usbusb_desc = devm_kzalloc(&pdev->dev,sizeof(struct power_supply_desc), GFP_KERNEL);if (usb_desc == NULL) {ret = -ENOMEM;goto err_desc_alloc_failed;}usb_desc->properties = sprdbat_usb_props;usb_desc->num_properties = ARRAY_SIZE(sprdbat_usb_props);usb_desc->get_property = sprdbat_usb_get_property;usb_desc->name = "usb";usb_desc->type = POWER_SUPPLY_TYPE_USB;usb_desc->no_thermal = true;usb_cfg.drv_data = sprdbat_data;ret_ptr = power_supply_register(&pdev->dev, battery_desc, &battery_cfg);if (IS_ERR(ret_ptr)) {goto err_battery_failed;} else {data->battery = ret_ptr;data->battery->supplied_to = battery_supply_list;data->battery->num_supplicants =ARRAY_SIZE(battery_supply_list);}ret_ptr = power_supply_register(&pdev->dev, ac_desc, &ac_cfg);if (IS_ERR(ret_ptr)) {goto err_ac_failed;} else {data->ac = ret_ptr;data->ac->supplied_to = supply_list;data->ac->num_supplicants = ARRAY_SIZE(supply_list);}ret_ptr = power_supply_register(&pdev->dev, usb_desc, &usb_cfg);if (IS_ERR(ret_ptr)) {goto err_usb_failed;} else {data->usb = ret_ptr;data->usb->supplied_to = supply_list;data->usb->num_supplicants = ARRAY_SIZE(supply_list);}//注册ret_ptr = power_supply_register(&pdev->dev, battery_desc, &battery_cfg);if (IS_ERR(ret_ptr)) {goto err_battery_failed;} else {data->battery = ret_ptr;data->battery->supplied_to = battery_supply_list;data->battery->num_supplicants =ARRAY_SIZE(battery_supply_list);}ret_ptr = power_supply_register(&pdev->dev, ac_desc, &ac_cfg);if (IS_ERR(ret_ptr)) {goto err_ac_failed;} else {data->ac = ret_ptr;data->ac->supplied_to = supply_list;data->ac->num_supplicants = ARRAY_SIZE(supply_list);}ret_ptr = power_supply_register(&pdev->dev, usb_desc, &usb_cfg);if (IS_ERR(ret_ptr)) {goto err_usb_failed;} else {data->usb = ret_ptr;data->usb->supplied_to = supply_list;data->usb->num_supplicants = ARRAY_SIZE(supply_list);}

3.接下来我们看看power_supply_decs和power_supply_config这两个结构体：
power_supply_decs结构体：

dir：//kernel/include/linux/power_supply.h/* Description of power supply */
struct power_supply_desc {const char *name;                                                         //名字enum power_supply_type type;                                            //类型，usb,battery这种       enum power_supply_property *properties;                                 //属性，就是这个power_supply设备具备的属性，类似battery 的POWER_SUPPLY_PROP_CAPACITY（电量）属性size_t num_properties;                                                  //属性的总数/** Functions for drivers implementing power supply class.* These shouldn't be called directly by other drivers for accessing* this power supply. Instead use power_supply_*() functions (for* example power_supply_get_property()).*/int (*get_property)(struct power_supply *psy,enum power_supply_property psp,union power_supply_propval *val);                          //在c编程中，我们叫函数指针，我们也可以抽象的认为是类编程中的抽象方法，就是要实现一个获取属性的函数int (*set_property)(struct power_supply *psy,enum power_supply_property psp,const union power_supply_propval *val);                        //同上，获取属性/** property_is_writeable() will be called during registration* of power supply. If this happens during device probe then it must* not access internal data of device (because probe did not end).*/int (*property_is_writeable)(struct power_supply *psy,enum power_supply_property psp);                      //同上void (*external_power_changed)(struct power_supply *psy);void (*set_charged)(struct power_supply *psy);/** Set if thermal zone should not be created for this power supply.* For example for virtual supplies forwarding calls to actual* sensors or other supplies.*/bool no_thermal;                                                      //这个power_supply设备是否支持thermal（温度相关，防止高温烧坏器件等等）/* For APM emulation, think legacy userspace. */int use_for_apm;
};

// power_supply_config结构体，好像没有什么好介绍的

/* Run-time specific power supply configuration */
struct power_supply_config {struct device_node *of_node; /* Driver private data */void *drv_data;char **supplied_to;size_t num_supplicants;
};

power_supply 结构体

struct power_supply {const struct power_supply_desc *desc;char **supplied_to;size_t num_supplicants;char **supplied_from;size_t num_supplies;struct device_node *of_node;/* Driver private data */void *drv_data;/* private */struct device dev;struct work_struct changed_work; //为每个power_supply设备创建一个工作队列，在调用power_supply_changed的时候调用struct delayed_work deferred_register_work; //为每个power_supply设备创建一个延时工作队列，在第一次调用power_supply_register的时候会调用，用来通知应用层，以便实现数据更新spinlock_t changed_lock;bool changed;atomic_t use_cnt;
#ifdef CONFIG_THERMALstruct thermal_zone_device *tzd;struct thermal_cooling_device *tcd;
#endif#ifdef CONFIG_LEDS_TRIGGERSstruct led_trigger *charging_full_trig;char *charging_full_trig_name;struct led_trigger *charging_trig;char *charging_trig_name;struct led_trigger *full_trig;char *full_trig_name;struct led_trigger *online_trig;char *online_trig_name;struct led_trigger *charging_blink_full_solid_trig;char *charging_blink_full_solid_trig_name;
#endif
};

3.power_supply_regitser源码分析：

static struct power_supply *__must_check
__power_supply_register(struct device *parent,const struct power_supply_desc *desc,const struct power_supply_config *cfg,bool ws)
{struct device *dev;struct power_supply *psy;int rc;if (!parent)pr_warn("%s: Expected proper parent device for '%s'\n",__func__, desc->name);psy = kzalloc(sizeof(*psy), GFP_KERNEL);if (!psy)return ERR_PTR(-ENOMEM);dev = &psy->dev;device_initialize(dev);                               //初始化设备结构体dev->class = power_supply_class;                      //设备类dev->type = &power_supply_dev_type;                        //设备类型dev->parent = parent;                                 //设备父节点dev->release = power_supply_dev_release;dev_set_drvdata(dev, psy);                               //设置设备的私有指针psy->desc = desc;                                        //power supply desc if (cfg) {                                              //power supply config 结构体psy->drv_data = cfg->drv_data;psy->of_node = cfg->of_node;psy->supplied_to = cfg->supplied_to;psy->num_supplicants = cfg->num_supplicants;}rc = dev_set_name(dev, "%s", desc->name);             //命名设备名if (rc)goto dev_set_name_failed;INIT_WORK(&psy->changed_work, power_supply_changed_work);//初始化power_supply_changed工作队列INIT_DELAYED_WORK(&psy->deferred_register_work,          //初始化power_supply_regiser延时工作队列power_supply_deferred_register_work);rc = power_supply_check_supplies(psy);                     //在链表中查询实例power_supply是否存在if (rc) {dev_info(dev, "Not all required supplies found, defer probe\n");goto check_supplies_failed;}spin_lock_init(&psy->changed_lock);rc = device_init_wakeup(dev, ws);if (rc)goto wakeup_init_failed;rc = device_add(dev);                                      //将设备添加到设备层if (rc)goto device_add_failed;rc = psy_register_thermal(psy);                               //注册thermal ,如果no_thermal，则相当于无操作if (rc)goto register_thermal_failed;rc = psy_register_cooler(psy);if (rc)goto register_cooler_failed;rc = power_supply_create_triggers(psy);                      //注册led的触发器if (rc)goto create_triggers_failed;/** Update use_cnt after any uevents (most notably from device_add()).* We are here still during driver's probe but* the power_supply_uevent() calls back driver's get_property* method so:* 1. Driver did not assigned the returned struct power_supply,* 2. Driver could not finish initialization (anything in its probe*    after calling power_supply_register()).*/atomic_inc(&psy->use_cnt);                                  //记数加1queue_delayed_work(system_power_efficient_wq,             //每个电源应用注册后，延时调用power_supply_changed来更新下数据&psy->deferred_register_work,POWER_SUPPLY_DEFERRED_REGISTER_TIME);return psy;create_triggers_failed:psy_unregister_cooler(psy);
register_cooler_failed:psy_unregister_thermal(psy);
register_thermal_failed:device_del(dev);
device_add_failed:
wakeup_init_failed:
check_supplies_failed:
dev_set_name_failed:put_device(dev);return ERR_PTR(rc);
}/*** power_supply_register() - Register new power supply* @parent:    Device to be a parent of power supply's device, usually*       the device which probe function calls this* @desc: Description of power supply, must be valid through whole*       lifetime of this power supply* @cfg:   Run-time specific configuration accessed during registering,*       may be NULL** Return: A pointer to newly allocated power_supply on success* or ERR_PTR otherwise.* Use power_supply_unregister() on returned power_supply pointer to release* resources.*/
struct power_supply *__must_check power_supply_register(struct device *parent,const struct power_supply_desc *desc,const struct power_supply_config *cfg)
{return __power_supply_register(parent, desc, cfg, true);
}
EXPORT_SYMBOL_GPL(power_supply_register);

4.power_supply_changed源码分析：

static int __power_supply_changed_work(struct device *dev, void *data)
{struct power_supply *psy = data;struct power_supply *pst = dev_get_drvdata(dev);if (__power_supply_is_supplied_by(psy, pst)) {if (pst->desc->external_power_changed)pst->desc->external_power_changed(pst);}return 0;
}static void power_supply_changed_work(struct work_struct *work)
{unsigned long flags;struct power_supply *psy = container_of(work, struct power_supply,changed_work);dev_dbg(&psy->dev, "%s\n", __func__);spin_lock_irqsave(&psy->changed_lock, flags);/** Check 'changed' here to avoid issues due to race between* power_supply_changed() and this routine. In worst case* power_supply_changed() can be called again just before we take above* lock. During the first call of this routine we will mark 'changed' as* false and it will stay false for the next call as well.*/if (likely(psy->changed)) {psy->changed = false;spin_unlock_irqrestore(&psy->changed_lock, flags);class_for_each_device(power_supply_class, NULL, psy,__power_supply_changed_work);power_supply_update_leds(psy);                             //atomic_notifier_call_chain(&power_supply_notifier,            //事件通知链，主要用于内核通知PSY_EVENT_PROP_CHANGED, psy);kobject_uevent(&psy->dev.kobj, KOBJ_CHANGE);             // 通过uevnet来通知应用层，有数据需要更新。spin_lock_irqsave(&psy->changed_lock, flags);}/** Hold the wakeup_source until all events are processed.* power_supply_changed() might have called again and have set 'changed'* to true.*/if (likely(!psy->changed))pm_relax(&psy->dev);spin_unlock_irqrestore(&psy->changed_lock, flags);
}void power_supply_changed(struct power_supply *psy)
{unsigned long flags;dev_dbg(&psy->dev, "%s\n", __func__);spin_lock_irqsave(&psy->changed_lock, flags); //加自旋锁psy->changed = true;pm_stay_awake(&psy->dev);      //保持唤醒锁spin_unlock_irqrestore(&psy->changed_lock, flags);schedule_work(&psy->changed_work); //调度工作队列
}
EXPORT_SYMBOL_GPL(power_supply_changed);

总结：

总的来说：在驱动层浅显的理解power_supply框架就是：所有power_supply设备通过实现power_supply_decs结构体的填充实现，来实现对power_supply设备具备的属性描述，诸如：battery具备capacity, ac具备online这种，然后再实现对其拥有属性的设置和读取的函数，最后调用power_supply_register()将该power_supply设备注册上去。最后通过power_supply_changed（）来将power_supply设备有数据变化通过uevent告诉应用层。

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