This is a fix for mkb jingpad devices.
If you can successfully flash the official .pac file to your jingpad, but its screen is always black ......
Check the serial number of your device, if it has "mkb" in it, then your jingpad is probably an engineering device (and the "mkc" device is for users), which means the jingling team sent you the wrong device.
If this happens, you can compile the Android source code with this fix provided by Chinese user @追梦人.