Android7.0 降低屏幕亮度（MTK）

在源码 kernel-3.18/drivers/misc/mediatek/video/common/aal20/ddp_pwm.c

        if(g_is_tv101wum_wuxga_dsi_vdo){
                PWM_NOTICE("set g_is_tv101wum_wuxga_dsi_vdo lcd backlight level_1024=%d\n",level_1024); 
-               tmp = level_1024 * 65/100;                                  //这个值是屏幕最终的亮度值，给这个值*xx% ，可以使屏幕亮度值按比例降低
+#ifdef CONFIG_TV101WUM_LOW_BRIGHTNESS
+               printk("CONFIG_TV101WUM_LOW_BRIGHTNESS def\n");
+               tmp = level_1024 * 40/100 * 65/100;
+#else
+               printk("CONFIG_TV101WUM_LOW_BRIGHTNESS not def\n");
+               tmp = level_1024 * 65/100 * 55/100;
+#endif