亮度设置
应用设计
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
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
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 * * [email protected]} */ 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 +2934
public void setBacklightBrightness(int brightness) { mContext.enforceCallingOrSelfPermission(android.Manifest.permission.DEVICE_POWER, null); // Don't let applications turn the screen all the way off synchronized (mLocks) { brightness = Math.max(brightness, mScreenBrightnessDim); mLcdLight.setBrightness(brightness); mKeyboardLight.setBrightness(mKeyboardVisible ? brightness : 0); mButtonLight.setBrightness(brightness); long identity = Binder.clearCallingIdentity(); try { mBatteryStats.noteScreenBrightness(brightness); } catch (RemoteException e) { Slog.w(TAG, "RemoteException calling noteScreenBrightness on BatteryStatsService", e); } finally { Binder.restoreCallingIdentity(identity); } // update our animation state synchronized (mLocks) { mScreenBrightness.targetValue = brightness; mScreenBrightness.jumpToTargetLocked(); } } }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/LightsService.java
public void setBrightness(int brightness, int brightnessMode) { synchronized (this) { Resources resources = mContext.getResources(); int mScreenBrightnessDim = resources.getInteger( com.android.internal.R.integer.config_screenBrightnessDim); brightness = Math.max(brightness, mScreenBrightnessDim); int color = brightness & 0x000000ff; color = 0xff000000 | (color << 16) | (color << 8) | color; setLightLocked(color, 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 <<
| 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 硬件调用
3.1获取硬件
文件：frameworks/base/services/jni/com_android_server_LightsService.cpp +129
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); devices->lights[LIGHT_INDEX_BLUETOOTH] = get_device(module, LIGHT_ID_BLUETOOTH); devices->lights[LIGHT_INDEX_WIFI] = get_device(module, LIGHT_ID_WIFI); } 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_by_class(const char *class_id, const char *inst, 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]; char name[PATH_MAX]; if (inst) snprintf(name, PATH_MAX, "%s.%s", class_id, inst); else strlcpy(name, class_id, 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_PATH2, name, prop); if (access(path, R_OK) == 0) break; snprintf(path, sizeof(path), "%s/%s.%s.so", HAL_LIBRARY_PATH1, name, prop); if (access(path, R_OK) == 0) break; } else { snprintf(path, sizeof(path), "%s/%s.default.so", HAL_LIBRARY_PATH1, name); if (access(path, R_OK) == 0) 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(class_id, path, module); } return status;}int hw_get_module(const char *id, const struct hw_module_t **module){ return hw_get_module_by_class(id, NULL, module);}}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。
3.2调用硬件
setLight_native对应的jni C/C++代码是：
文件：frameworks/base/frameworks/base/services/jni/com_android_server_LightsService.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 硬件原型
msm7k的lights对应的硬件原型是在：hardware/msm7k/liblights
文件：hardware/msm7k/liblights/Android.mk
LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hw
LOCAL_MODULE := lights.$(TARGET_BOARD_PLATFORM)
也就是生成模块：/system/lib/hw/lights. msm7k.so
文件：device/softwinner/crane-common/hardware/libhardware/lights/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); LOGD("open_lights!name = %s\n",name); 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_context_t *dev = (struct light_context_t *)malloc(sizeof(struct light_context_t)); memset(dev, 0, sizeof(struct light_context_t)); LOGD("light set back linghts!name = %s\n",name); if(0 == strcmp(LIGHT_ID_BACKLIGHT, name)) { dev->fd = open("/dev/disp", O_RDONLY); if (dev->fd < 0) { LOGE("Failed to open display device dev->fd = %x\n",dev->fd); } } dev->device.common.tag = HARDWARE_DEVICE_TAG; dev->device.common.version = 0; dev->device.common.module = (struct hw_module_t*)module; dev->device.common.close = (int (*)(struct hw_device_t*))close_lights; dev->device.set_light = set_light; *device = (struct hw_device_t*)dev; return 0;error: free(dev); return -EINVAL;}static struct hw_module_methods_t lights_module_methods = { .open = open_lights,};以上代码对应的是：
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);
也就是说，对不同的亮度设置给予了不同的设置函数。
举例，背光设置，背光对应的代码如下：
static intrgb_to_brightness(struct light_state_t const* state){ int color = state->color & 0x00ffffff; int bright; bright = ((77*((color>>16)&0x00ff)) + (150*((color>>8)&0x00ff)) + (29*(color&0x00ff))) >> 8; //support backlight 0-255// bright = bright >> 4; /* fix bright value >=5 , for HW reason*/ if(bright < 5) bright = 5; return bright;}static intset_light_backlight(struct light_device_t* dev, struct light_state_t const* state){ struct light_context_t *ctx; int err = 0; int brightness = rgb_to_brightness(state); pthread_mutex_lock(&g_lock); g_backlight = brightness; ctx = (struct light_context_t *)dev; unsigned long args[3]; args[0] = 0; args[1] = brightness; args[2] = 0; err = ioctl(ctx->fd,DISP_CMD_LCD_SET_BRIGHTNESS,args); if(err == 0) { g_backlight = brightness; } pthread_mutex_unlock(&g_lock); return err;}然后驱动层
vendor/softwinner/linux-3.0/drivers/video/sun4i/disp/dev_disp.c
vendor/softwinner/linux-3.0/drivers/video/sun4i/disp/de_bsp/de/disp_lcd.c +1739
写寄存器
__s32 pwm_set_duty_ns(__u32 channel, __u32 duty_ns){ __u32 active_cycle = 0; __u32 tmp; active_cycle = (duty_ns * gdisp.pwm[channel].entire_cycle + (gdisp.pwm[channel].period_ns/2)) / gdisp.pwm[channel].period_ns; if(channel == 0) { tmp = pwm_read_reg(0x204); pwm_write_reg(0x204,(tmp & 0xffff0000) | active_cycle); } else { tmp = pwm_read_reg(0x208); pwm_write_reg(0x208,(tmp & 0xffff0000) | active_cycle); } gdisp.pwm[channel].duty_ns = duty_ns; DE_INF("%d,%d,%d,%d\n", duty_ns, gdisp.pwm[channel].period_ns, active_cycle, gdisp.pwm[channel].entire_cycle); return 0;}//.....static __s32 pwm_write_reg(__u32 offset, __u32 value){ sys_put_wvalue(gdisp.init_para.base_pwm+offset, value); LCD_delay_ms(20); return 0;}