android: lcd backlight

1. packages/apps/Settings/src/com/Android/settings/BrightnessPreference.java

2.frameworks/base/core/java/Android/os/IPowerManager.aidl.java
   --> // sets the brightness of the backlights (screen, keyboard, button) 0-255
    void setBacklightBrightness(int brightness)

3.frameworks/base/core/java/Android/os/PowerManager.java

    public void setBacklightBrightness(int brightness)
    { 
        try {
            mService.setBacklightBrightness(brightness);
        } catch (RemoteException e) { 
        }
    } 


4.frameworks/base/services/java/com/Android/server/PowerManagerService.java

 -- >public void setBacklightBrightness(int brightness) {   

5.frameworks/base/services/java/com/android/server/LightsService.java

 public void setBrightness(int brightness) {
            setBrightness(brightness, BRIGHTNESS_MODE_USER);
        }

        public void setBrightness(int brightness, int brightnessMode) {
            synchronized (this) {         
                int color = brightness & 0x000000ff;
                color = 0xff000000 | (color << 16) | (color << 8) | color;
                setLightLocked(color, LIGHT_FLASH_NONE, 0, 0, brightnessMode);
            }
        }







6./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);

}

7. devices/vendor/board/liblights.c


set_light_backlight(struct light_device_t* dev,
        struct light_state_t const* state)                                                                                                                             
{
    int err = 0;
    int brightness = rgb_to_brightness(state);                                                                                                                         
    int fd;
    char buf[1]={0};

    pthread_mutex_lock(&g_lock);  
    fd = open(LCD_FILE, O_RDONLY);
    err=read(fd, &buf, 1);
    close(fd);
    if(buf[0] == '0' && brightness)   
        usleep(200000);
    err = write_int(LCD_FILE, brightness);
    pthread_mutex_unlock(&g_lock);                                                                                                                                     

    return err;
}

char const*const LCD_FILE
        = "/sys/class/leds/lcd-backlight/brightness";




8. kernel/driver/leds
ex: kernel/driver/leds/xxxx-pwm.c