android backlight
背光設(shè)置是在：設(shè)置->聲音和顯示->亮度，通過(guò)進(jìn)度條來(lái)設(shè)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);
設(shè)置進(jìn)度條的范圍，BRIGHTNESS_DIM = 20? BRIGHTNESS_ON=255，它們的定義在：
frameworks/base/core/java/android/os/Power.java
3.1.2 設(shè)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) {
???????????
??????? }???????
}
由以上代碼可知，brightness的范圍是：20~255;代碼通過(guò)服務(wù)管理器(ServiceManager)獲得power服務(wù)，然后通過(guò)power服務(wù)設(shè)置亮度。
power.setBacklightBrightness的定義在：
rameworks/base/core/java/android/os/IPowerManager.aidl.java
frameworks/base/core/java/android/os/PowerManager.java
3.2 Power服務(wù)
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) {
??????? }
}
電源管理器(powermager)將brightness轉(zhuǎn)給電源服務(wù)，該服務(wù)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;
??????? }
??? }
由以上代碼可知，同時(shí)設(shè)置了背光、鍵盤(pán)、按鈕的亮度。mHardware 是硬件服務(wù)，通過(guò)該服務(wù)調(diào)用底層與設(shè)備打交道的C/C++代碼，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);
??? }
參數(shù)說(shuō)明：int light 表示類(lèi)型，選項(xiàng)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，選項(xiàng)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;
由代碼：
int b = brightness & 0x000000ff;
??????? b = 0xff000000 | (b << 16) | (b << 8) | b;
可知，亮度值在此進(jìn)行了修改，即亮度值的格式變成：FFRRGGBB，FF是沒(méi)有的，RR、GG、BB分別是256色的紅綠藍(lán)，并且紅綠藍(lán)的值都是一樣的亮度值。
3.3 硬件調(diào)用
3.3.1獲取硬件
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獲取ID為L(zhǎng)IGHTS_HARDWARE_MODULE_ID的硬件模塊，該模塊含有6個(gè)不同類(lèi)型的亮度控制。
hw_get_module 的實(shí)現(xiàn)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) 會(huì)按如下順序去獲取如下變量所對(duì)應(yīng)的值，然后返回給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"
它們對(duì)應(yīng)的變量為：
"ro.product.board=$TARGET_BOOTLOADER_BOARD_NAME"
"ro.board.platform=$TARGET_BOARD_PLATFORM"
如vendor/htc/dream-open/BoardConfig.mk里定義的TARGET_BOARD_PLATFORM := msm7k，則prop返回” msm7k ”，所以path = /system/lib/hw/lights. msm7k.so，也就是說(shuō)要獲取的硬件模塊為lights. msm7k.so。
3.3.2調(diào)用硬件
setLight_native對(duì)應(yīng)的jni C/C++代碼是：
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);
}
通過(guò)light標(biāo)識(shí)找到對(duì)應(yīng)的light設(shè)備，然后再設(shè)置亮度。
3.3.3 硬件原型
msm7k的lights對(duì)應(yīng)的硬件原型是在：hardware/msm7k/liblights
文件：hardware/msm7k/liblights/Android.mk
LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hw
LOCAL_MODULE := lights.$(TARGET_BOARD_PLATFORM)
?
也就是生成模塊：/system/lib/hw/lights. msm7k.so
?
文件：hardware/msm7k/liblights/lights.c
/** Open a new instance of a lights device using name */
static int open_lights(const struct hw_module_t* module, char const* name,
??????? struct hw_device_t** device)
{
??? int (*set_light)(struct light_device_t* dev,
??????????? struct light_state_t const* state);
?
??? if (0 == strcmp(LIGHT_ID_BACKLIGHT, name)) {
??????? set_light = set_light_backlight;
??? }
??? else if (0 == strcmp(LIGHT_ID_KEYBOARD, name)) {
??????? set_light = set_light_keyboard;
??? }
??? else if (0 == strcmp(LIGHT_ID_BUTTONS, name)) {
??????? set_light = set_light_buttons;
??? }
??? else if (0 == strcmp(LIGHT_ID_BATTERY, name)) {
??????? set_light = set_light_battery;
??? }
??? else if (0 == strcmp(LIGHT_ID_NOTIFICATIONS, name)) {
??????? set_light = set_light_notifications;
??? }
??? else if (0 == strcmp(LIGHT_ID_ATTENTION, name)) {
??????? set_light = set_light_attention;
??? }
??? else {
??????? return -EINVAL;
??? }
?
??? pthread_once(&g_init, init_globals);
?
??? struct light_device_t *dev = malloc(sizeof(struct light_device_t));
??? memset(dev, 0, sizeof(*dev));
?
??? dev->common.tag = HARDWARE_DEVICE_TAG;
??? dev->common.version = 0;
??? dev->common.module = (struct hw_module_t*)module;
??? dev->common.close = (int (*)(struct hw_device_t*))close_lights;
??? dev->set_light = set_light;
?
??? *device = (struct hw_device_t*)dev;
??? return 0;
}
static struct hw_module_methods_t lights_module_methods = {
??? .open =? open_lights,
};
以上代碼對(duì)應(yīng)的是：
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);
也就是說(shuō)，對(duì)不同的亮度設(shè)置給予了不同的設(shè)置函數(shù)。
舉例，背光設(shè)置，背光對(duì)應(yīng)的代碼如下：
char const*const LCD_FILE
??????? = "/sys/class/leds/lcd-backlight/brightness";
static int
rgb_to_brightness(struct light_state_t const* state)
{
??? int color = state->color & 0x00ffffff;
??? return ((77*((color>>16)&0x00ff))
??????????? + (150*((color>>8)&0x00ff)) + (29*(color&0x00ff))) >> 8;
}
static int
set_light_backlight(struct light_device_t* dev,
??????? struct light_state_t const* state)
{
??? int err = 0;
??? int brightness = rgb_to_brightness(state);
??? pthread_mutex_lock(&g_lock);
??? g_backlight = brightness;
????err = write_int(LCD_FILE, brightness);
??? if (g_haveTrackballLight) {
??????? handle_trackball_light_locked(dev);
??? }
?? ?pthread_mutex_unlock(&g_lock);
??? return err;
}
也就是往文件/sys/class/leds/lcd-backlight/brightness寫(xiě)入亮度值，然后驅(qū)動(dòng)會(huì)根據(jù)該文件更改背光的亮度。LCD_FILE的路徑根據(jù)實(shí)際情況更改，同時(shí)需要在init.rc 修改其權(quán)限，使其可寫(xiě)rgb_to_brightness也根據(jù)實(shí)際更改，比如要直接亮度值控制，那只要獲取r,g,b其中的一個(gè)值就行了，如：
static int
rgb_to_brightness(struct light_state_t const* state)
{
??? int color = state->color & 0x000000ff;
??? return color;
}
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