Android: Android Light Sensor HOWTO

基于android 2.2 添加Light Sensor支持：

1) UI部分

2) framework部分

3) HAL 部分

4) Driver 部分

下面分别讨论:

1) UI部分

a) 打开亮度设置菜单的自动调整亮度checkbox

frameworks/base/core/res/res/values/config.xml :

- <boolname="config_automatic_brightness_available">false</bool>

+<boolname="config_automatic_brightness_available">true</bool>

b) 同时设置Lux级，亮度级，以5级亮度为例

<integer-arrayname="config_autoBrightnessLevels">

+<item>1000</item>

+<item>2000</item>

+<item>3000</item>

+<item>4000</item>

</integer-array>

<integer-arrayname="config_autoBrightnessLcdBacklightValues">

+<item>20</item>

+<item>80</item>

+<item>120</item>

+<item>160</item>

+<item>250</item>

</integer-array>

autoBrightnessLevels 随便设，HAL层传上来的数据落在这几个值之间以区分级别

LcdBacklightValues 是5级亮度的实际值

2)framework部分

a) framework层的相关文件

./core/java/android/hardware/SensorEvent.java

./core/java/android/hardware/SensorListener.java

./core/java/android/hardware/ISensorService.aidl

./core/java/android/hardware/Sensor.java

./core/java/android/hardware/SensorEventListener.java

./core/jni/android_hardware_SensorManager.cpp //SensorManager JNI

./core/java/android/hardware/SensorManager.java //SensorManager

./services/jni/com_android_server_SensorService.cpp //SensorSersvice JNI

./services/java/com/android/server/SensorService.java //SensorService

./services/java/com/android/server/PowerManagerService.java

Sensor系统相对比较简单，我们需要修改的更少：

添加Light Sensor只需要修改SensorManager.java,PowerManagerService.java两个文件

b)SensorManager.java:

@@ -582,6 +582,8 @@ public class SensorManager return SENSOR_ORIENTATION_RAW; case Sensor.TYPE_TEMPERATURE: return SENSOR_TEMPERATURE; + case Sensor.TYPE_LIGHT: + return SENSOR_LIGHT; } return 0; } @@ -606,6 +608,9 @@ public class SensorManager result |= SensorManager.SENSOR_ORIENTATION | SensorManager.SENSOR_ORIENTATION_RAW; break; + case Sensor.TYPE_LIGHT: + result |= SensorManager.SENSOR_LIGHT; + break; } } return result; @@ -707,6 +712,8 @@ public class SensorManager listener, sensors, rate) || result; result = registerLegacyListener(SENSOR_TEMPERATURE, Sensor.TYPE_TEMPERATURE, listener, sensors, rate) || result; + result = registerLegacyListener(SENSOR_LIGHT, Sensor.TYPE_LIGHT, + listener, sensors, rate) || result; return result; } @@ -766,6 +773,8 @@ public class SensorManager listener, sensors); unregisterLegacyListener(SENSOR_TEMPERATURE, Sensor.TYPE_TEMPERATURE, listener, sensors); + unregisterLegacyListener(SENSOR_LIGHT, Sensor.TYPE_LIGHT, + listener, sensors); }

c)PowerManagerService.java:

这里似乎一个系统bug

int lcdValue = getAutoBrightnessValue( - (mIsDocked ? value : mHighestLightSensorValue), - mLcdBacklightValues); + (true ? value : mHighestLightSensorValue), + mLcdBacklightValues);

3) HAL 部分

实现hardware/libhardware/include/hardware/sensor.h接口，写一个HAL层，

这部分请参考我上一篇文章: android sensor HAL范例，那个例子写的好级啦

需要说明的一点是，android系统的所有sensor公用一个HAL层文件，所以如果你的系统已有其他sensor那么需要在其他

sensor的HAL实现中添加light sensor

HAL层最终生成 /system/lib/hw/sensors.xxx.so

4) Driver 部分

不管啥接口的light sensor，请把它写成一个input设备，

通过/dev/input/eventX来提供数据

这样在HAL层polling的时候就可以

nread = read(ls_fd, &event, sizeof(event));

if (event->type == EV_ABS) { LOGV("light-level type: %d code: %d value: %-5d time: %ds", event->type, event->code, event->value, (int)event->time.tv_sec); if (event->code == EVENT_TYPE_LIGHT) { struct input_absinfo absinfo; int index; if (!ioctl(fd, EVIOCGABS(ABS_DISTANCE), &absinfo)) { index = event->value; if (index >= 0) { new_sensors |= SENSORS_LIGHT; if (index >= ARRAY_SIZE(sLuxValues)) { index = ARRAY_SIZE(sLuxValues) - 1; } dev->sensors[ID_L].light = sLuxValues[index]; } } } }

.light 最终传给 PowerManager,PowerManager根据config_autoBrightnessLevels数组

得到config_autoBrightnessLcdBacklightValues数据具体亮度值，然后调整亮度

比如 .light = 2500.0

3000.0< 2500.0 < 4000.0 对应的LcdBacklightValues 就是160

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