imx8背光控制原理

本文主要是介绍imx8背光控制原理，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

backlight

参考文档

android lcd 背光控制流程

error

[ 1286.086494] vehicle_rpmsg virtio0.rpmsg-vehicle-channel.-1.1: rpmsg_send timeout!
[ 1286.086543] send message failed!
06-27 07:05:48.557  2595  2595 I CAR.POWER: send display brightness = 29
[ 1286.088031] this type is not correct!

Service rpmsg调用

• packages/services/Car/service/src/com/android/car/hal/PowerHalService.java

  /*** Sets the display brightness for the vehicle.* @param brightness value from 0 to 100.*/
  public void sendDisplayBrightness(int brightness) {if (brightness < 0) {brightness = 0;} else if (brightness > 100) {brightness = 100;}try {mHal.set(VehicleProperty.DISPLAY_BRIGHTNESS, 0).to(brightness);           <--------- 修改Log.i(CarLog.TAG_POWER, "send display brightness = " + brightness);       <--------- 修改} catch (PropertyTimeoutException e) {Log.e(CarLog.TAG_POWER, "cannot set DISPLAY_BRIGHTNESS", e);}
  }
  

• sendDisplayBrightness

  wugn@wugn:Car$ grep sendDisplayBrightness * -R
  service/src/com/android/car/hal/PowerHalService.java:    public void sendDisplayBrightness(int brightness) {
  service/src/com/android/car/systeminterface/DisplayInterface.java:                        mService.sendDisplayBrightness(percentBright);
  service/src/com/android/car/CarPowerManagementService.java:    public void sendDisplayBrightness(int brightness) {
  service/src/com/android/car/CarPowerManagementService.java:        mHal.sendDisplayBrightness(brightness);
  

HAL 调用

• frameworks/base/services/core/jni/com_android_server_lights_LightsService.cpp

  static void processReturn(const Return<Status> &ret,Type type,const LightState &state) {if (!ret.isOk()) {ALOGE("Failed to issue set light command.");LightHal::disassociate();return;}switch (static_cast<Status>(ret)) {case Status::SUCCESS:break;case Status::LIGHT_NOT_SUPPORTED:ALOGE("Light requested not available on this device. %d", type);break;case Status::BRIGHTNESS_NOT_SUPPORTED:ALOGE("Brightness parameter not supported on this device: %d",state.brightnessMode);break;case Status::UNKNOWN:default:ALOGE("Unknown error setting light.");}
  }static void setLight_native(JNIEnv* /* env */,jobject /* clazz */,jint light,jint colorARGB,jint flashMode,jint onMS,jint offMS,jint brightnessMode) {if (!validate(light, flashMode, brightnessMode)) {return;}sp<ILight> hal = LightHal::associate();if (hal == nullptr) {return;}Type type = static_cast<Type>(light);LightState state = constructState(colorARGB, flashMode, onMS, offMS, brightnessMode);{android::base::Timer t;Return<Status> ret = hal->setLight(type, state);processReturn(ret, type, state);if (t.duration() > 50ms) ALOGD("Excessive delay setting light");}
  }
  

• setLight_native()—>set_light ()，对应调用的是set_light_backlight来设置背光
• vendor/nxp-opensource/imx/lights/fsl_lights.c

  /*****************************************************************************/
  static int lights_device_open(const struct hw_module_t* module,const char* name, struct hw_device_t** device)
  {int status = -EINVAL;ALOGV("lights_device_open\n");if (!strcmp(name, LIGHT_ID_BACKLIGHT)) {struct light_device_t *dev;char value[PROPERTY_VALUE_MAX];FILE *file;dev = malloc(sizeof(*dev));/* initialize our state here */memset(dev, 0, sizeof(*dev));/* initialize the procs */dev->common.tag = HARDWARE_DEVICE_TAG;dev->common.version = 0;dev->common.module = (struct hw_module_t*) module;dev->common.close = light_close_backlight;dev->set_light = set_light_backlight;*device = &dev->common;property_get("hw.backlight.dev", value, DEF_BACKLIGHT_DEV);strcpy(path, DEF_BACKLIGHT_PATH);strcat(path, value);strcpy(max_path, path);strcat(max_path, "/max_brightness");strcat(path, "/brightness");file = fopen(max_path, "r");if (!file) {// free(dev);                                                                            <--------- 修改ALOGE("cannot open backlight file %s [%s]\n", max_path,strerror(errno));// return status;                                                                        <--------- 修改} else {fclose(file);}ALOGI("max backlight file is %s\n", max_path);ALOGI("backlight brightness file is %s\n", path);status = 0;}/* todo other lights device init */return status;
  }
  

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