Android架构解析之亮度设置-2.1版本

http://blog.csdn.net/skdev/archive/2010/03/01/5335554.aspx

3 亮度设置

3.1 应用设计

3.1.1 设置进度条范围

背光设置是在：设置->声音和显示->亮度，通过进度条来设置的。

文件：packages/apps/Settings/src/com/android/settings/BrightnessPreference.java

private static final int MINIMUM_BACKLIGHT = android.os.Power.BRIGHTNESS_DIM + 10;

private static final int MAXIMUM_BACKLIGHT = android.os.Power.BRIGHTNESS_ON;

mSeekBar.setMax(MAXIMUM_BACKLIGHT - MINIMUM_BACKLIGHT);

设置进度条的范围，BRIGHTNESS_DIM = 20? BRIGHTNESS_ON=255，它们的定义在：

frameworks/base/core/java/android/os/Power.java

3.1.2 设置亮度

文件：packages/apps/Settings/src/com/android/settings/BrightnessPreference.java

public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

?????? setMode(isChecked ? Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC

??????????????? : Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL);

??????? if (!isChecked) {

??????????? setBrightness(mSeekBar.getProgress() + MINIMUM_BACKLIGHT);

??????? }

??? }

private void setBrightness(int brightness) {

??????? try {

??????????? IPowerManager power = IPowerManager.Stub.asInterface(

??????????????????? ServiceManager.getService("power"));

??????????? if (power != null) {

??????????????? power.setBacklightBrightness(brightness);

??? ????????}

??????? } catch (RemoteException doe) {

???????????

??????? }???????

}

由以上代码可知，brightness的范围是：20~255;代码通过服务管理器(ServiceManager)获得power服务，然后通过power服务设置亮度。

power.setBacklightBrightness的定义在：

rameworks/base/core/java/android/os/IPowerManager.aidl.java

frameworks/base/core/java/android/os/PowerManager.java

3.2 Power服务

文件：frameworks/base/core/java/android/os/Power.java

/**

???? * Brightness value for dim backlight

???? */

??? public static final int BRIGHTNESS_DIM = 20;

?

??? /**

???? * Brightness value for fully on

???? */

public static final int BRIGHTNESS_ON = 255;

文件：frameworks/base/core/java/android/os/PowerManager.java

/**

???? * sets the brightness of the backlights (screen, keyboard, button).

???? *

???? * @param brightness value from 0 to 255

? ???*

???? * {@hide}

???? */

??? public void setBacklightBrightness(int brightness)

??? {

??????? try {

??????????? mService.setBacklightBrightness(brightness);

??????? } catch (RemoteException e) {

??????? }

}

电源管理器(powermager)将brightness转给电源服务，该服务位置如下：

文件：frameworks/base/services/java/com/android/server/PowerManagerService.java

public void setBacklightBrightness(int brightness) {

??????? mContext.enforceCallingOrSelfPermission(android.Manifest.permission.DEVICE_POWER, null);

??????? // Don't let applications turn the screen all the way off

??????? brightness = Math.max(brightness, Power.BRIGHTNESS_DIM);

??????? mHardware.setLightBrightness_UNCHECKED(HardwareService.LIGHT_ID_BACKLIGHT, brightness,

??????????????? HardwareService.BRIGHTNESS_MODE_USER);

????? ??mHardware.setLightBrightness_UNCHECKED(HardwareService.LIGHT_ID_KEYBOARD,

??????????? (mKeyboardVisible ? brightness : 0), HardwareService.BRIGHTNESS_MODE_USER);

??????? mHardware.setLightBrightness_UNCHECKED(HardwareService.LIGHT_ID_BUTTONS, brightness,

??????????? HardwareService.BRIGHTNESS_MODE_USER);

??????? long identity = Binder.clearCallingIdentity();

??????? try {

??????????? mBatteryStats.noteScreenBrightness(brightness);

??????? } catch (RemoteException e) {

??????????? Log.w(TAG, "RemoteException calling noteScreenBrightness on BatteryStatsService", e);

??????? } finally {

??????????? Binder.restoreCallingIdentity(identity);

??????? }

?

??????? // update our animation state

??????? if (ANIMATE_SCREEN_LIGHTS) {

??????????? mScreenBrightness.curValue = brightness;

??????????? mScreenBrightness.animating = false;

??????????? mScreenBrightness.targetValue = -1;

??????? }

??????? if (ANIMATE_KEYBOARD_LIGHTS) {

??????????? mKeyboardBrightness.curValue = brightness;

??????????? mKeyboardBrightness.animating = false;

??????????? mKeyboardBrightness.targetValue = -1;

??????? }

??????? if (ANIMATE_BUTTON_LIGHTS) {

??????????? mButtonBrightness.curValue = brightness;

??????????? mButtonBrightness.animating = false;

??????????? mButtonBrightness.targetValue = -1;

??????? }

??? }

由以上代码可知，同时设置了背光、键盘、按钮的亮度。mHardware 是硬件服务，通过该服务调用底层与设备打交道的C\C++代码，setLightBrightness_UNCHECKED原型如下：

文件：frameworks/base/services\java\com\android\server\HardwareService.java

void setLightBrightness_UNCHECKED(int light, int brightness, int brightnessMode) {

??????? int b = brightness & 0x000000ff;

??????? b = 0xff000000 | (b << 16) | (b << 8) | b;

??????? setLight_native(mNativePointer, light, b, LIGHT_FLASH_NONE, 0, 0, brightnessMode);

??? }

参数说明：int light 表示类型，选项如下：

static final int LIGHT_ID_BACKLIGHT = 0;

??? static final int LIGHT_ID_KEYBOARD = 1;

??? static final int LIGHT_ID_BUTTONS = 2;

??? static final int LIGHT_ID_BATTERY = 3;

??? static final int LIGHT_ID_NOTIFICATIONS = 4;

static final int LIGHT_ID_ATTENTION = 5;

int brightness 表示亮度值

int brightnessMode 表示亮度的控制模式，选项如下：

/**

???? * Light brightness is managed by a user setting.

???? */

??? static final int BRIGHTNESS_MODE_USER = 0;

?

??? /**

???? * Light brightness is managed by a light sensor.

???? */

static final int BRIGHTNESS_MODE_SENSOR = 1;

由代码：

int b = brightness & 0x000000ff;

??????? b = 0xff000000 | (b << 16) | (b << 8) | b;

可知，亮度值在此进行了修改，即亮度值的格式变成：FFRRGGBB，FF是没有的，RR、GG、BB分别是256色的红绿蓝，并且红绿蓝的值都是一样的亮度值。

3.3 硬件调用

3.3.1获取硬件

文件：frameworks/base/services/jni/com_android_server_HardwareService.cpp

enum {

?? ?LIGHT_INDEX_BACKLIGHT = 0,

??? LIGHT_INDEX_KEYBOARD = 1,

??? LIGHT_INDEX_BUTTONS = 2,

??? LIGHT_INDEX_BATTERY = 3,

??? LIGHT_INDEX_NOTIFICATIONS = 4,

??? LIGHT_INDEX_ATTENTION = 5,

??? LIGHT_COUNT

};

?

#define LIGHTS_HARDWARE_MODULE_ID "lights"

?

static jint 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);

??? } else {

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

??? }

?

??? return (jint)devices;

}

用hw_get_module获取ID为LIGHTS_HARDWARE_MODULE_ID的硬件模块，该模块含有6个不同类型的亮度控制。

hw_get_module 的实现原理，如下：

文件：hardware/libhardware/Hardware.c

#define HAL_LIBRARY_PATH "/system/lib/hw"

static const char *variant_keys[] = {

??? "ro.hardware",? /* This goes first so that it can pick up a different

?????????????????????? file on the emulator. */

??? "ro.product.board",

??? "ro.board.platform",

??? "ro.arch"

};

?

static const int HAL_VARIANT_KEYS_COUNT =

??? (sizeof(variant_keys)/sizeof(variant_keys[0]));

int hw_get_module(const char *id, const struct hw_module_t **module)

{

??? int status;

??? int i;

??? const struct hw_module_t *hmi = NULL;

??? char prop[PATH_MAX];

??? char path[PATH_MAX];

?

??? /*

???? * Here we rely on the fact that calling dlopen multiple times on

???? * the same .so will simply increment a refcount (and not load

???? * a new copy of the library).

???? * We also assume that dlopen() is thread-safe.

???? */

?

??? /* Loop through the configuration variants looking for a module */

??? for (i=0 ; i<HAL_VARIANT_KEYS_COUNT+1 ; i++) {

??????? if (i < HAL_VARIANT_KEYS_COUNT) {

??????????? if (property_get(variant_keys[i], prop, NULL) == 0) {

??????????????? continue;

??????????? }

??????????? snprintf(path, sizeof(path), "%s/%s.%s.so",

??????????????????? HAL_LIBRARY_PATH, id, prop);

?? ?????} else {

??????????? snprintf(path, sizeof(path), "%s/%s.default.so",

??????????????????? HAL_LIBRARY_PATH, id);

??????? }

??????? if (access(path, R_OK)) {

??????????? continue;

??????? }

??????? /* we found a library matching this id/variant */

??? ????break;

??? }

?

??? status = -ENOENT;

??? if (i < HAL_VARIANT_KEYS_COUNT+1) {

??????? /* load the module, if this fails, we're doomed, and we should not try

???????? * to load a different variant. */

??????? status = load(id, path, module);

??? }

?

??? return status;

}

property_get(variant_keys[i], prop, NULL) 会按如下顺序去获取如下变量所对应的值，然后返回给prop：

"ro.hardware",? /* This goes first so that it can pick up a different

?????????????????????? file on the emulator. */

??? "ro.product.board",

??? "ro.board.platform",

"ro.arch"

它们对应的变量为：

"ro.product.board=$TARGET_BOOTLOADER_BOARD_NAME"

"ro.board.platform=$TARGET_BOARD_PLATFORM"

如vendor/htc/dream-open/BoardConfig.mk里定义的TARGET_BOARD_PLATFORM := msm7k，则prop返回” msm7k ”，所以path = /system/lib/hw/lights. msm7k.so，也就是说要获取的硬件模块为lights. msm7k.so。

setLight_native对应的jni C/C++代码是：

文件：frameworks/base/services/jni/com_android_server_HardwareService.cpp

static void setLight_native(JNIEnv *env, jobject clazz, int ptr,

??????? int light, int colorARGB, int flashMode, int onMS, int offMS, int brightnessMode)

{

??? Devices* devices = (Devices*)ptr;

??? light_state_t state;

?

??? if (light < 0 || light >= LIGHT_COUNT || devices->lights[light] == NULL) {

??????? return ;

??? }

?

??? memset(&state, 0, sizeof(light_state_t));

??? state.color = colorARGB;

??? state.flashMode = flashMode;

??? state.flashOnMS = onMS;

??? state.flashOffMS = offMS;

??? state.brightnessMode = brightnessMode;

?

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

}

通过light标识找到对应的light设备，然后再设置亮度。

3.3.3 硬件原型

msm7k的