If you have a working Brightness Slider and you might be using Brightness slider or manual hotkeys to control brightness then this guide may help you to use your Native hotkeys of laptop.
(All the Credits goes to @RehabMan For OS-X-ACPI-Debug Kext and DSDT Patches.)
This step assumes that you are using RehabMan's VoodooPS2Controller
Install the kext: https://github.com/RehabMan/OS-X-ACPI-Debug
Open MaciASL and click on patch.(Add rehab man repo) Apply "Add DSDT Debug Methods" and "Instrument EC Queries" that are under Brightness Fix. Save the DSDT and restart Look in Syslog as you press the key corresponding to brightness to determine which _QXX methods handle the keys Then patch DSDT:
into method label _Q1D replace_content
// Brightness Down\n
into method label _Q1C replace_content
// Brightness Up\n
Change the variable _Q1D/_Q1C as per the log.
7. Try compiling and check if it generates errors 8. If it does, then change the PS2M to PS2X according to the one found in your DSDT 9. Save and place the compiled DSDT. 10. Now you should see that you have your corresponding keys to change your brightness
FOR more detail and Queries,Check Out original Post of @RehabMan Here;
Get Latest Version of OS-X-ACPI-Debug kext here: