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1、前言

充电LED灯控制是Android设备的基本功能，主要用于提示设备的电池状态，充电状态，满电状态，低电状态，很多手机厂商还使用呼吸效果来显示，普通的低端设备会使用两个LED灯表示，红灯表示充电和低电，绿灯表示满电。

2、kernel 层控制充电LED

代码位置主要在kernel/driver/power/power_supply_leds.c

/* Battery specific LEDs triggers. */

static void power_supply_update_bat_leds(struct power_supply *psy)

{

    union power_supply_propval status;

    unsigned long delay_on = 0;

    unsigned long delay_off = 0;

    if (power_supply_get_property(psy, POWER_SUPPLY_PROP_STATUS, &status))

        return;

    dev_dbg(&psy->dev, "%s %d\n", __func__, status.intval);

    switch (status.intval) {

    case POWER_SUPPLY_STATUS_FULL:

        led_trigger_event(psy->charging_full_trig, LED_FULL);

        led_trigger_event(psy->charging_trig, LED_OFF);

        led_trigger_event(psy->full_trig, LED_FULL);

        led_trigger_event(psy->charging_blink_full_solid_trig,

            LED_FULL);

        break;

    case POWER_SUPPLY_STATUS_CHARGING:

        led_trigger_event(psy->charging_full_trig, LED_FULL);

        led_trigger_event(psy->charging_trig, LED_FULL);

        led_trigger_event(psy->full_trig, LED_OFF);

        led_trigger_blink(psy->charging_blink_full_solid_trig,

            &delay_on, &delay_off);

        break;

    default:

        led_trigger_event(psy->charging_full_trig, LED_OFF);

        led_trigger_event(psy->charging_trig, LED_OFF);

        led_trigger_event(psy->full_trig, LED_OFF);

        led_trigger_event(psy->charging_blink_full_solid_trig,

            LED_OFF);

        break;

    }

}

如果想在kernel 层控制led灯，就需要在这里修改代码，会需要使用到trigger相关的东西，要理解什么是trigger，可以看下面的链接

https://blog.csdn.net/sgmenghuo/article/details/38322141

trigger主要是做led灯的一些效果的东西，默认有default-on 对应打开led的trigger，还有none对应关闭LED的trigger。

被[ ]括起来的，就是当前trigger的值，然后回触发对应trigger的.activate函数。

Trigger的代码位置在 kernel/drivers/leds/trigger

3、framework控制led灯

为了统一控制led接口，Android有一个自己的框架控制led灯

Framework->Hal->kernel->hardware

设置对应的LED灯颜色主要在

Framework/base/core/res/res/values/config.xml

    <color name="config_defaultNotificationColor">#ffffffff</color>

    <!-- Default LED on time for notification LED in milliseconds. -->

    <integer name="config_defaultNotificationLedOn">500</integer>

    <!-- Default LED off time for notification LED in milliseconds. -->

    <integer name="config_defaultNotificationLedOff">2000</integer>

    <!-- Default value for led color when battery is low on charge -->

    <integer name="config_notificationsBatteryLowARGB">0xFFFF0000</integer>                                            

    <!-- Default value for led color when battery is medium charged -->

    <integer name="config_notificationsBatteryMediumARGB">0xFFFF0000</integer>

    <!-- Default value for led color when battery is fully charged -->

    <integer name="config_notificationsBatteryFullARGB">0xFF00FF00</integer>

    <!-- Default value for LED on time when the battery is low on charge in miliseconds -->

    <integer name="config_notificationsBatteryLedOn">125</integer>

充电状态灯指示状态函数调用

frameworks\base\services\core\java\com\android\server\BatteryService.java

/**

* Synchronize on BatteryService.

*/

public void updateLightsLocked() {

final int level = mBatteryProps.batteryLevel;

final int status = mBatteryProps.batteryStatus;

if (level < mLowBatteryWarningLevel) {

    if (status == BatteryManager.BATTERY_STATUS_CHARGING) {

        // Solid red when battery is charging

        mBatteryLight.setColor(mBatteryLowARGB);

    } else {

        // Flash red when battery is low and not charging

        mBatteryLight.setFlashing(mBatteryLowARGB, Light.LIGHT_FLASH_TIMED,

        mBatteryLedOn, mBatteryLedOff);

    }

} else if (status == BatteryManager.BATTERY_STATUS_CHARGING

|| status == BatteryManager.BATTERY_STATUS_FULL) {

    if (status == BatteryManager.BATTERY_STATUS_FULL || level >= 90) {

    // Solid green when full or charging and nearly full

        mBatteryLight.setColor(mBatteryFullARGB);

    } else {

        if (isHvdcpPresent()) {

            // Blinking orange if HVDCP charger

            mBatteryLight.setFlashing(mBatteryMediumARGB, Light.LIGHT_FLASH_TIMED,

            mBatteryLedOn, mBatteryLedOn);

        } else {

            // Solid orange when charging and halfway full

            mBatteryLight.setColor(mBatteryMediumARGB);

        }

    }

} else {

    // No lights if not charging and not low

    mBatteryLight.turnOff();

}

}

}

LightsService 管理LED

frameworks\base\services\core\java\com\android\server\lights\LightsService.java

private void setLightLocked(int color, int mode, int onMS, int offMS, int brightnessMode)；

{

//调用JNI函数设置状态

setLight_native(mNativePointer, mId, color, mode, onMS, offMS, brightnessMode);

}

static void setLight_native(JNIEnv* /* env */, jobject /* clazz */, jlong ptr,jint light, jint colorARGB, jint flashMode, jint onMS, jint offMS, jint brightnessMode)

{

//调用HAL层接口设置指示灯状态

devices->lights[light]->set_light(devices->lights[light], &state);

}

获取HAL层接口函数

static jlong init_native(JNIEnv* /* env */, jobject /* clazz */)

{

int err;

hw_module_t* module;

Devices* devices;

devices = (Devices*)malloc(sizeof(Devices));

err = hw_get_module(LIGHTS_HARDWARE_MODULE_ID, (hw_module_t const**)&module);

if (err == 0) {

    devices->lights[LIGHT_INDEX_BACKLIGHT] = get_device(module, LIGHT_ID_BACKLIGHT);

    devices->lights[LIGHT_INDEX_KEYBOARD] = get_device(module, LIGHT_ID_KEYBOARD);

    devices->lights[LIGHT_INDEX_BUTTONS] = get_device(module, LIGHT_ID_BUTTONS);

    devices->lights[LIGHT_INDEX_BATTERY] = get_device(module, LIGHT_ID_BATTERY);

    devices->lights[LIGHT_INDEX_NOTIFICATIONS] = get_device(module, LIGHT_ID_NOTIFICATIONS);

    devices->lights[LIGHT_INDEX_ATTENTION] = get_device(module, LIGHT_ID_ATTENTION);

    devices->lights[LIGHT_INDEX_BLUETOOTH] = get_device(module, LIGHT_ID_BLUETOOTH);

    devices->lights[LIGHT_INDEX_WIFI] = get_device(module, LIGHT_ID_WIFI);

} else {

    memset(devices, 0, sizeof(Devices));

}

return (jlong)devices;

}

中间层的代码位置主要在

Hardware/rockchip/liblight/

一个字节对应一种颜色，一共有三个颜色，想最终控制颜色就需要修改上面说的xml文件，比如0x00ffffff,表示红蓝绿三个灯同时亮。具体代码如下

int set_battery_light(struct light_device_t* dev, struct light_state_t const* state)

{                                     

    int err = 0;                      

    char red,blue,green;              

    unsigned int colorRGB = state->color & 0x00ffffff;

    red = (colorRGB >> 16) & 0xFF; 

    green = (colorRGB >> 8) & 0xFF;                                                                                    

    blue = colorRGB & 0xFF;           

    pthread_mutex_lock(&g_lock);   

    LOGI(">>>weiqifa set_battery_light 0x%x",state->color);

    err = write_int(RED_LED_PATH, red?1:0);

    err = write_int(BLUE_LED_PATH, blue?1:0);

    err = write_int(GREEN_LED_PATH, green?1:0);

    pthread_mutex_unlock(&g_lock); 

    return 0;                         

}    

然后控制的主要是led的设备节点，led的设备节点主要是驱动层生成，代码的位置如下：kernel/driver/leds/

#define RED_LED_PATH "sys/class/leds/red/brightness"

#define GREEN_LED_PATH "sys/class/leds/green/brightness"

#define BLUE_LED_PATH "sys/class/leds/blue/brightness"

Led驱动对应的dts代码如下：

   leds: gpio-leds {

        compatible = "gpio-leds";

        led-green {

        ┊   label = "green";

            gpios = <&gpio7 8 GPIO_ACTIVE_HIGH>;

            inux,default-trigger = "timer";

            default-state = "off";

        }; 

        led-blue {

        ┊   label = "blue";

            gpios = <&gpio7 14 GPIO_ACTIVE_HIGH>;

            inux,default-trigger = "timer";

            default-state = "off";

        }; 

        led-red {

        ┊   label = "red";

            gpios = <&gpio7 15 GPIO_ACTIVE_HIGH>;

            inux,default-trigger = "timer";                                                                            

            default-state = "off";

        };

    };  

里面的linux,default-trigger 表示默认的trigger模式，如果设置为none就是表示关闭，现在我们的代码设置为timer表示用定时器的模式，实际上我们没有编译定时器模式，所以设置并没有生效。