android（linux）背光流程

1. 上层处理

PowerManagerService.java (frameworks\base\services\java\com\android\server)

private LightsService.Light mLcdLight;    private void setLightBrightness(int mask, int value) {        int brightnessMode = (mAutoBrightessEnabled                            ? LightsService.BRIGHTNESS_MODE_SENSOR                            : LightsService.BRIGHTNESS_MODE_USER);        if ((mask & SCREEN_BRIGHT_BIT) != 0) {            if (DEBUG_SCREEN_ON) {                RuntimeException e = new RuntimeException("here");                e.fillInStackTrace();                Slog.i(TAG, "Set LCD brightness: " + value, e);            }            mLcdLight.setBrightness(value, brightnessMode);        }        if ((mask & BUTTON_BRIGHT_BIT) != 0) {            mButtonLight.setBrightness(value);        }        if ((mask & KEYBOARD_BRIGHT_BIT) != 0) {            mKeyboardLight.setBrightness(value);        }    }

LightsService.java (frameworks\base\services\java\com\android\server)

        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);            }        }        private void setLightLocked(int color, int mode, int onMS, int offMS, int brightnessMode) {            if (color != mColor || mode != mMode || onMS != mOnMS || offMS != mOffMS) {                if (DEBUG) Slog.v(TAG, "setLight #" + mId + ": color=#"                        + Integer.toHexString(color));                mColor = color;                mMode = mode;                mOnMS = onMS;                mOffMS = offMS;                setLight_native(mNativePointer, mId, color, mode, onMS, offMS, brightnessMode);            }        }

2. JNI 处理

com_android_server_LightsService.cpp（/framework/base/services/jni/）

static JNINativeMethod method_table[] = {      { "init_native", "()I", (void*)init_native },      { "finalize_native", "(I)V", (void*)finalize_native },      { "setLight_native", "(IIIIIII)V", (void*)setLight_native },

static light_device_t* get_device(hw_module_t* module, char const* name)  {      int err;      hw_device_t* device;      err = module->methods->open(module, name, &device);      if (err == 0) {          return (light_device_t*)device;      } else {          return NULL;      }  }    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;  }         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);  }

3. 底层处理

Lights.c (device\marvell\***\lights)

const char * const LCD_BACKLIGHT = "/sys/class/backlight/pwm-backlight.2/brightness";  static int lights_device_open(const struct hw_module_t *module,                  const char *name, struct hw_device_t **device);    static struct hw_module_methods_t lights_module_methods = {      .open      = lights_device_open  };    struct light_module_t  {      struct hw_module_t common;  };    const struct light_module_t HAL_MODULE_INFO_SYM = {      common: {          tag : HARDWARE_MODULE_TAG,          version_major : 1,          version_minor : 0,          id : LIGHTS_HARDWARE_MODULE_ID,          name : "lights module",          author : "",          methods : &lights_module_methods,      }  };    int lights_set(struct light_device_t* dev, struct light_state_t const* state, const char* brightness_node) {      struct light_state_t const *light_state = (struct light_state_t const*)state;      unsigned char brightness = 0;      int fd = -1;      struct my_light_device_t *mydev = (struct my_light_device_t*)dev;      if( light_state ) {          unsigned int color = light_state->color;          brightness = (color & 0xff) * mydev->max_brightness / 0xff;      } else {          LOGE("lights_set_brightness failed: light state is null\n");          return -EINVAL;      }      fd = open(brightness_node, O_RDWR);      if( fd >= 0 ) {          char buffer[20];          int bytes = sprintf(buffer, "%d", brightness);          int rlt = write(fd, buffer, bytes);          if( rlt < 0 ){              LOGE("lights_set_brightness %s, fail to set brightness to:%s, errno:%d\n", brightness_node, buffer, errno);               close(fd);              return -1;          }          close(fd);      } else {          static int already_warned = 0;          if (already_warned < 5) {              LOGE("lights_set_brightness failed to open %s, errno:%d\n", brightness_node, errno);              already_warned++;          }          return -1;      }      return 0;  }  int lights_set_lcd(struct light_device_t* dev, struct light_state_t const* state)  {      return lights_set( dev, state, LCD_BACKLIGHT);  }    static int lights_device_open(const struct hw_module_t *module,                  const char *name, struct hw_device_t **device)  {      int status = -EINVAL;      int ret;  #ifdef LIGHTS_DEBUG      LOGD("lights_device_open: device name: %s\n", name);  #endif        struct light_device_t *dev = NULL;      struct my_light_device_t *mydev = NULL;            mydev = (struct my_light_device_t *)calloc(sizeof(struct my_light_device_t), 1);      dev = &(mydev->dev);      dev->common.tag = HARDWARE_DEVICE_TAG;      dev->common.version = 0;      dev->common.module = (struct hw_module_t *)(module);      dev->common.close = lights_device_close;        mydev->max_brightness = 0xff;//default max brightness is 255                *device = &dev->common;            if (!strcmp(name, LIGHT_ID_BACKLIGHT)) {          dev->set_light = lights_set_lcd;          readIntFromFile( LCD_MAX_BACKLIGHT, &mydev->max_brightness);          ret = access(LCD_BACKLIGHT, F_OK);          if (ret != 0)              return status;      } else if (!strcmp(name, LIGHT_ID_KEYBOARD)) {          dev->set_light = lights_set_keyboard;          readIntFromFile( KEYBOARD_MAX_BACKLIGHT, &mydev->max_brightness);          ret = access(KEYBOARD_BACKLIGHT, F_OK);          if (ret != 0)              return status;      } else if (!strcmp(name, LIGHT_ID_BUTTONS)) {          dev->set_light = lights_set_button;          ret = access(BUTTON_BACKLIGHT, F_OK);          if (ret != 0)              return status;      } else if (!strcmp(name, LIGHT_ID_BATTERY)) {          dev->set_light = lights_set_battery;          ret = access(BATTERY_BACKLIGHT, F_OK);          if (ret != 0)              return status;      } else if (!strcmp(name, LIGHT_ID_NOTIFICATIONS)) {          dev->set_light = lights_set_notifications;          ret = access(NOTIFICATIONS_BACKLIGHT, F_OK);          if (ret != 0)              return status;      } else if (!strcmp(name, LIGHT_ID_ATTENTION)) {          dev->set_light = lights_set_attention;          ret = access(ATTENTION_BACKLIGHT, F_OK);          if (ret != 0)              return status;      } else          return status;            return 0;  }

ps:

节点创建位置：

configs/XXX/init/copyfiles/root/init.pxa988.rc

chown system system /sys/class/backlight/pwm-backlight.4/brightness

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