Android(安卓)振动器(Vibrator)系统

Android 振动器系统是Android其他系统中相对简单的系统。振动器系统用来移动电话的震动功能。比如闹钟、振动模式都需要用到振动器系统。

平台 MTK6573

Android 振动器系统架构

1 驱动层

2 硬件抽象层

2 JNI框架层

3 Java应用层

一、驱动层

Android修改、新增Linux内核文件

/kernel/drivers/staging/android/timed_output.h

/kernel/drivers/staging/android/timed_output.c

timed_output.h 定义了timed_output_dev 结构体

struct timed_output_dev {const char*name;/* enable the output and set the timer */void(*enable)(struct timed_output_dev *sdev, int timeout);/* returns the current number of milliseconds remaining on the timer */int(*get_time)(struct timed_output_dev *sdev);/* private data */struct device*dev;intindex;intstate;};

timed_output.c 实现了该结构体，使用函数timed_output_dev_register实现注册，使用timed_output_dev_unregister实现注销。

int timed_output_dev_register(struct timed_output_dev *tdev){int ret;if (!tdev || !tdev->name || !tdev->enable || !tdev->get_time)return -EINVAL;ret = create_timed_output_class();if (ret < 0)return ret;tdev->index = atomic_inc_return(&device_count);tdev->dev = device_create(timed_output_class, NULL,MKDEV(0, tdev->index), NULL, tdev->name);if (IS_ERR(tdev->dev))return PTR_ERR(tdev->dev);ret = device_create_file(tdev->dev, &dev_attr_enable);if (ret < 0)goto err_create_file;dev_set_drvdata(tdev->dev, tdev);tdev->state = 0;return 0;err_create_file:device_destroy(timed_output_class, MKDEV(0, tdev->index));printk(KERN_ERR "timed_output: Failed to register driver %s\n",tdev->name);return ret;}EXPORT_SYMBOL_GPL(timed_output_dev_register);void timed_output_dev_unregister(struct timed_output_dev *tdev){device_remove_file(tdev->dev, &dev_attr_enable);device_destroy(timed_output_class, MKDEV(0, tdev->index));dev_set_drvdata(tdev->dev, NULL);}EXPORT_SYMBOL_GPL(timed_output_dev_unregister);

驱动实现移植

以MTK 6573平台为例

./mediatek/platform/mt6573/kernel/drivers/vibrator/vibrator.c

操作设备

首先打开手机调试，连接USB，执行adb shell，进入/sys/devices/timed_output/vibrator/

执行echo "10000" enable发现手机在震动

# echo "10000" enableecho "10000" enable10000 enable

执行 cat enable 可以查看当前震动时间剩余数

# cat enablecat enable0

二、硬件抽象层

Android 封装了对底层驱动的调用，成为硬件抽象层。

/hardware/libhardware_legacy/vibrator/vibrator.c

int vibrator_on(int timeout_ms){    /* constant on, up to maximum allowed time */    return sendit(timeout_ms);}int vibrator_off(){    return sendit(0);}

提供了vibrato_on 和vibrator_off 两个函数用来操作振动器

static int sendit(int timeout_ms){    int nwr, ret, fd;    char value[20];    fd = open(THE_DEVICE, O_RDWR);    if(fd < 0)        return errno;     nwr = sprintf(value, "%d\n", timeout_ms);    ret = write(fd, value, nwr);     close(fd);     return (ret == nwr) ? 0 : -1;}

三、 JNI框架层

Android JNI框架层是方便Java调用C/C++方法。

./frameworks/base/services/jni/com_android_server_VibratorService.cpp

namespace android {  static void vibratorOn(JNIEnv *env, jobject clazz, jlong timeout_ms) {     // LOGI("vibratorOn\n");     vibrator_on(timeout_ms); } static void vibratorOff(JNIEnv *env, jobject clazz) {     // LOGI("vibratorOff\n");     vibrator_off(); } static JNINativeMethod method_table[] = {     { "vibratorOn", "(J)V", (void*)vibratorOn },     { "vibratorOff", "()V", (void*)vibratorOff } }; int register_android_server_VibratorService(JNIEnv *env) {     return jniRegisterNativeMethods(env, "com/android/server/VibratorService",             method_table, NELEM(method_table)); }};

四、Java应用层

这层包括Java 应用的调用，Android系统服务Java层

./frameworks/base/services/java/com/android/server/VibratorService.java

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