安卓9.0馬達框架分析

安卓9.0馬達框架分析

關鍵詞：mt8167s；Android 9.0

前言

​ 最近需要將之前的一些驅動接口轉爲安卓標準接口，方便上層應用或者第三方應用去適配。這篇文章先從簡單的馬達框架入手進行講解。

正文

​ 整個馬達框架比較簡單，安卓官方已經幫我們實現了framework到HAL層，我們需要實現的就只有驅動層。這篇文章我們梳理一下從上層到底層怎麼流程。

1、APP層

import android.os.Vibrator;
import android.widget.ToggleButton;

public class MainActivity extends Activity {
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		private Vibrator vibrator=null;
		vibrator=(Vibrator)this.getSystemService(VIBRATOR_SERVICE);
		toggleButton1=(ToggleButton)findViewById(R.id.toggleButton1);
		/*短震動*/
		toggleButton1.setOnCheckedChangeListener(new ToggleButton.OnCheckedChangeListener() {
			
			@Override
			public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
				if(isChecked){
                    Log.i(TAG,"toggleButton1 enter vibrator.vibrate");
					//設置震動週期，第二個參數爲 -1表示只震動一次
					vibrator.vibrate(new long[]{1000, 10, 100, 1000},-1);
				}else{
					//取消震動
                    Log.i(TAG,"toggleButton1 enter vibrator.cancel()");
					vibrator.cancel();
				}
			}
		});
	}
}

​ 上面展示了一個最簡單的馬達震動應用代碼，獲得服務後即可調用接口進行驅動。

2、framework層

代碼路徑：frameworks\base\services\core\java\com\android\server\VibratorService.java

    @Override // Binder call
    public void vibrate(int uid, String opPkg, VibrationEffect effect, int usageHint,
            IBinder token) {
        Trace.traceBegin(Trace.TRACE_TAG_VIBRATOR, "vibrate");
        try {
            if (mContext.checkCallingOrSelfPermission(android.Manifest.permission.VIBRATE)
                    != PackageManager.PERMISSION_GRANTED) {
                throw new SecurityException("Requires VIBRATE permission");
            }
            if (token == null) {
                Slog.e(TAG, "token must not be null");
                return;
            }
            verifyIncomingUid(uid);
            if (!verifyVibrationEffect(effect)) {
                return;
            }

            // If our current vibration is longer than the new vibration and is the same amplitude,
            // then just let the current one finish.
            synchronized (mLock) {
                if (effect instanceof VibrationEffect.OneShot
                        && mCurrentVibration != null
                        && mCurrentVibration.effect instanceof VibrationEffect.OneShot) {
                    VibrationEffect.OneShot newOneShot = (VibrationEffect.OneShot) effect;
                    VibrationEffect.OneShot currentOneShot =
                            (VibrationEffect.OneShot) mCurrentVibration.effect;
                    if (mCurrentVibration.hasTimeoutLongerThan(newOneShot.getDuration())
                            && newOneShot.getAmplitude() == currentOneShot.getAmplitude()) {
                        if (DEBUG) {
                            Slog.d(TAG,
                                    "Ignoring incoming vibration in favor of current vibration");
                        }
                        return;
                    }
                }

                // If the current vibration is repeating and the incoming one is non-repeating,
                // then ignore the non-repeating vibration. This is so that we don't cancel
                // vibrations that are meant to grab the attention of the user, like ringtones and
                // alarms, in favor of one-shot vibrations that are likely quite short.
                if (!isRepeatingVibration(effect)
                        && mCurrentVibration != null
                        && isRepeatingVibration(mCurrentVibration.effect)) {
                    if (DEBUG) {
                        Slog.d(TAG, "Ignoring incoming vibration in favor of alarm vibration");
                    }
                    return;
                }

                Vibration vib = new Vibration(token, effect, usageHint, uid, opPkg);
                linkVibration(vib);
                long ident = Binder.clearCallingIdentity();
                try {
                    doCancelVibrateLocked();
                    startVibrationLocked(vib);
                    addToPreviousVibrationsLocked(vib);
                } finally {
                    Binder.restoreCallingIdentity(ident);
                }
            }
        } finally {
            Trace.traceEnd(Trace.TRACE_TAG_VIBRATOR);
        }
    }

​ 接口裏面會判斷一下權限，根據應用層傳遞的不同effect值，有不同的震動效果。然後就調用到JNI層，調用順序大概如下：

startVibrationLocked
	startVibrationInnerLocked
		doVibratorOn
			vibratorOn

3、JNI層

代碼路徑：frameworks\base\services\core\jni\com_android_server_VibratorService.cpp

static void vibratorOn(JNIEnv* /* env */, jobject /* clazz */, jlong timeout_ms)
{
    Status retStatus = halCall(&V1_0::IVibrator::on, timeout_ms).withDefault(Status::UNKNOWN_ERROR);
    if (retStatus != Status::OK) {
        ALOGE("vibratorOn command failed (%" PRIu32 ").", static_cast<uint32_t>(retStatus));
    }
}

static void vibratorOff(JNIEnv* /* env */, jobject /* clazz */)
{
    Status retStatus = halCall(&V1_0::IVibrator::off).withDefault(Status::UNKNOWN_ERROR);
    if (retStatus != Status::OK) {
        ALOGE("vibratorOff command failed (%" PRIu32 ").", static_cast<uint32_t>(retStatus));
    }
}

static const JNINativeMethod method_table[] = {
    { "vibratorExists", "()Z", (void*)vibratorExists },
    { "vibratorInit", "()V", (void*)vibratorInit },
    { "vibratorOn", "(J)V", (void*)vibratorOn },
    { "vibratorOff", "()V", (void*)vibratorOff },
    { "vibratorSupportsAmplitudeControl", "()Z", (void*)vibratorSupportsAmplitudeControl},
    { "vibratorSetAmplitude", "(I)V", (void*)vibratorSetAmplitude},
    { "vibratorPerformEffect", "(JJ)J", (void*)vibratorPerformEffect}
};

int register_android_server_VibratorService(JNIEnv *env)
{
    return jniRegisterNativeMethods(env, "com/android/server/VibratorService",
            method_table, NELEM(method_table));
}

以馬達的On和off爲例，會調用到HAL層的on和off方法。

4、HIDL層

代碼路徑：hardware\interfaces\vibrator\1.0\default\Vibrator.cpp

Return<Status> Vibrator::on(uint32_t timeout_ms) {
    int32_t ret = mDevice->vibrator_on(mDevice, timeout_ms);
    if (ret != 0) {
        ALOGE("on command failed : %s", strerror(-ret));
        return Status::UNKNOWN_ERROR;
    }
    return Status::OK;
}

Return<Status> Vibrator::off()  {
    int32_t ret = mDevice->vibrator_off(mDevice);
    if (ret != 0) {
        ALOGE("off command failed : %s", strerror(-ret));
        return Status::UNKNOWN_ERROR;
    }
    return Status::OK;
}

HIDL層是較新的安卓版本才引入的，是連接HAL層和JNI層的橋樑。

5、HAL層

代碼路徑：hardware\libhardware\modules\vibrator\vibrator.c

static const char THE_DEVICE[] = "/sys/class/timed_output/vibrator/enable";

static int sendit(unsigned int timeout_ms)
{
    char value[TIMEOUT_STR_LEN]; /* large enough for millions of years */

    snprintf(value, sizeof(value), "%u", timeout_ms);
    return write_value(THE_DEVICE, value);
}

static int vibra_on(vibrator_device_t* vibradev __unused, unsigned int timeout_ms)
{
    /* constant on, up to maximum allowed time */
    return sendit(timeout_ms);
}

static int vibra_off(vibrator_device_t* vibradev __unused)
{
    return sendit(0);
}

static int vibra_open(const hw_module_t* module, const char* id __unused,
                      hw_device_t** device __unused) {
    bool use_led;

    if (vibra_exists()) {
        ALOGD("Vibrator using timed_output");
        use_led = false;
    } else if (vibra_led_exists()) {
        ALOGD("Vibrator using LED trigger");
        use_led = true;
    } else {
        ALOGE("Vibrator device does not exist. Cannot start vibrator");
        return -ENODEV;
    }

    vibrator_device_t *vibradev = calloc(1, sizeof(vibrator_device_t));

    if (!vibradev) {
        ALOGE("Can not allocate memory for the vibrator device");
        return -ENOMEM;
    }

    vibradev->common.tag = HARDWARE_DEVICE_TAG;
    vibradev->common.module = (hw_module_t *) module;
    vibradev->common.version = HARDWARE_DEVICE_API_VERSION(1,0);
    vibradev->common.close = vibra_close;

    if (use_led) {
        vibradev->vibrator_on = vibra_led_on;
        vibradev->vibrator_off = vibra_led_off;
    } else {
        vibradev->vibrator_on = vibra_on;
        vibradev->vibrator_off = vibra_off;
    }

    *device = (hw_device_t *) vibradev;

    return 0;
}

​ 其實開啓和關閉馬達的工作很簡單，就是往節點"/sys/class/timed_output/vibrator/enable"寫入震動時間，所以可以想得到驅動層只需要提供一個節點供上層操作就好。

6、驅動層

​ 馬達的驅動是基於kernel提供的timed_output框架完成的：

代碼路徑：kernel-4.4\drivers\staging\android\timed_output.c

​ 代碼比較簡單，提供接口給驅動在"/sys/class/timed_output/"路徑下面建立自己的節點，並提供節點的device attribute的操作接口，當我們寫節點的時候就會調用到enable_store函數，並調用註冊驅動的enable函數。

static struct class *timed_output_class;

static ssize_t enable_store(struct device *dev, struct device_attribute *attr,
			    const char *buf, size_t size)
{
	struct timed_output_dev *tdev = dev_get_drvdata(dev);
	int value;
	int rc;

	rc = kstrtoint(buf, 0, &value);
	if (rc != 0)
		return -EINVAL;

	tdev->enable(tdev, value);

	return size;
}
static DEVICE_ATTR_RW(enable);

static struct attribute *timed_output_attrs[] = {
	&dev_attr_enable.attr,
	NULL,
};
ATTRIBUTE_GROUPS(timed_output);

static int create_timed_output_class(void)
{
	if (!timed_output_class) {
		timed_output_class = class_create(THIS_MODULE, "timed_output");
		if (IS_ERR(timed_output_class))
			return PTR_ERR(timed_output_class);
		atomic_set(&device_count, 0);
		timed_output_class->dev_groups = timed_output_groups;
	}

	return 0;
}

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, "%s", tdev->name);
	if (IS_ERR(tdev->dev))
		return PTR_ERR(tdev->dev);

	dev_set_drvdata(tdev->dev, tdev);
	tdev->state = 0;
	return 0;
}

​ 現在我們看一下基於上面框架書寫的馬達驅動：

static void vibrator_off(void)
{
	gpio_direction_output(gpio, !en_value);       
	wake_unlock(&vibdata.wklock); //震動關閉就可以釋放 wake_lock鎖        
}

void motor_enable(struct timed_output_dev *sdev,int value)
{
	mutex_lock(&vibdata.lock); //關鍵代碼段,同一時間只允許一個線程執行

	/* cancelprevious timer and set GPIO according to value */
	hrtimer_cancel(&vibdata.timer); //當先前定時器完成後 關閉這個定時器
	cancel_work_sync(&vibdata.work); //當上次震動完成後 關閉這次動作
	if(value)
	{
		wake_lock(&vibdata.wklock); //開始震動打開wake lock鎖不允許休眠
		gpio_direction_output(gpio, en_value);

		if(value > 0)
		{
			if(value > MAX_TIMEOUT)
				value= MAX_TIMEOUT;
			hrtimer_start(&vibdata.timer,
			         ktime_set(value / 1000, (value % 1000) * 1000000),
			         HRTIMER_MODE_REL);
		}
	}
	else
		vibrator_off();

	mutex_unlock(&vibdata.lock);
}

struct timed_output_dev motot_driver = {
	.name ="vibrator", //注意這個名字,由於HAL層裏面的設備爲//"/sys/class/timed_output/vibrator/enable"
	                   //因此這個名字必須爲"vibrator"
	.enable= motor_enable,
	.get_time= get_time,
};

static enum hrtimer_restart vibrator_timer_func(struct hrtimer *timer) //定時器結束時候的回調函數
{
	schedule_work(&vibdata.work); //定時器完成了 執行work隊列回調函數來關閉電機
	return HRTIMER_NORESTART;
}
static void vibrator_work(struct work_struct *work)
{
	vibrator_off();
}

static int motor_probe(struct platform_device *pdev)
{
	struct device_node *node = pdev->dev.of_node;
	enum of_gpio_flags flags;
	int ret =0;
	
	hrtimer_init(&vibdata.timer,CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	vibdata.timer.function= vibrator_timer_func;
	INIT_WORK(&vibdata.work,vibrator_work);

	...
	
	ret=timed_output_dev_register(&motot_driver);
	if (ret< 0)
		goto err_to_dev_reg;
	return 0;

err_to_dev_reg:
	mutex_destroy(&vibdata.lock);
	wake_lock_destroy(&vibdata.wklock);

	printk("vibrator   err!:%d\n",ret);
	return ret;

}

1、

​ 驅動接收上層傳遞過來的是震動時長，單位爲毫秒。在驅動裏註冊一個定時器，定時器倒計時到期後會喚醒註冊的工作隊列，最終會執行vibrator_work()函數去關閉馬達震動。

2、

​ 調用timed_output框架提供的timed_output_dev_register()接口將我們的馬達驅動註冊進系統，這裏的關鍵就是我們需要自定義struct timed_output_dev結構體，填充enable和get_time函數。enable函數用來開啓馬達的震動：

void motor_enable(struct timed_output_dev *sdev,int value)
{
	mutex_lock(&vibdata.lock); //關鍵代碼段,同一時間只允許一個線程執行

	/* cancelprevious timer and set GPIO according to value */
	hrtimer_cancel(&vibdata.timer); //當先前定時器完成後 關閉這個定時器
	cancel_work_sync(&vibdata.work); //當上次震動完成後 關閉這次動作
	if(value)
	{
		wake_lock(&vibdata.wklock); //開始震動打開wake lock鎖不允許休眠
		gpio_direction_output(gpio, en_value);

		if(value > 0)
		{
			if(value > MAX_TIMEOUT)
				value= MAX_TIMEOUT;
			hrtimer_start(&vibdata.timer,
			         ktime_set(value / 1000, (value % 1000) * 1000000),
			         HRTIMER_MODE_REL);
		}
	}
	else
		vibrator_off();

	mutex_unlock(&vibdata.lock);
}

​ 開啓震動的操作也很簡單，只是寫一下GPIO，然後重新開啓定時器，倒計時的時間就是寫入節點的值，到時間再把馬達關閉就好。

參考鏈接

https://blog.csdn.net/qq_34211365/article/details/105556842