There are many ways of accomplishing this. (For example, a new microcontroller may have a different IO address map and sending commands to the address of a peripheral on the old microcontroller will (1) prevent the peripheral from seeing the command and (2) likely unintentionally corrupt an unrelated register.)īecause of this, drivers, in general, are necessarily partially or wholly hardware-specific, so before a driver attempts to talk to hardware it needs to make sure that it's only targeting the exact hardware that it supports. If an old driver is used with new hardware, there is a strong likelihood that the backlight will either malfunction or not work at all. When they do, the driver software needs to be updated in order to add support for a new hardware implementation. It is critical to remember that Apple is free to change the implementation of the backlighting hardware between any two models of computer. Your output confirms that the necessary KEXTs are, in fact, loaded correctly. To do this, I asked you to check the output of kextstat and systemextensionsctl for the presence of backlight controller kernel extensions. So we should first check that the driver is present and loaded. If the driver isn't present and running, the system has no way to issue commands to the backlight controller to change the amount of electrical current it sends to the LED panel (i.e., changing the brightness).

This controller therefore requires driver software that is specifically written for the exact controller hardware used in your particular machine. The circuitry includes the LED backlighting panel itself along with a hardware controller for it which interfaces with the CPU and allows system (and user) software to command it.

The display backlight consists of dedicated circuitry and software components. So we should investigate each of these areas separately. Without additional information, this can mean a hardware, firmware, or software root cause. The fact that they occur simultaneously and that nothing appears to resolve them strongly suggests that there is a failure somewhere in the path of the display backlight chain. Now, both symptoms (A) and (B) can occur on their own for a number of different reasons.

You've noticed that (A) your display lacks a brightness slider and (B) the display won't turn on after sleep.

You've used third-party software to allow Catalina to be installed on a system which is too old to be natively supported.

2012 macbook pro screen issues