功能:设备没有lightsensor，需要调整为线性控制背光功能

1.frameworks/base/core/res/res/values/config.xml 中修改

config_screenBrightnessSettingMinimum 为1

2.frameworks/base/packages/SystemUI/src/com/android/systemui/settings/BrightnessController.java 中修改

添加转换函数

  private  final int convertGammaToLinearExt(int val, int min, int max) {
        final float normalizedVal = MathUtils.norm(0, GAMMA_SPACE_MAX, val);
        int value = (int) (normalizedVal*max);
        return value>0? value : 1;
   }
   private final int convertLinearToGammaExt(int val, int min, int max) {
       // For some reason, HLG normalizes to the range [0, 12] rather than [0, 1]
       final float normalizedVal = MathUtils.norm(0, max, val);
       return (int) (normalizedVal*GAMMA_SPACE_MAX);
   }

将文件中的convertGammaToLinear函数替换为convertGammaToLinearExt

将文件中的convertLinearToGamma函数替换为convertLinearToGammaExt

3.packages/apps/Settings/src/com/android/settings/display/BrightnessLevelPreferenceController.java 

添加方法

private final int convertLinearToGammaExt(int val, int min, int max) {
      // For some reason, HLG normalizes to the range [0, 12] rather than [0, 1]
       final float normalizedVal = MathUtils.norm(0, max, val);
       return (int) (normalizedVal*GAMMA_SPACE_MAX);
   }
convertLinearToGamma 方法替换为onvertLinearToGammaExt