Android架构解析之亮度设置-2.1版本
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
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
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。
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。
msm7k的
