GenericBrightness

General information

Goal

On some laptops, the screen brightness is not controlled by Intel registers. In that case, if your OEM ACPI methods are correct (this is rare but it does happen), you can use GenericBrightness. This is a simple kext that periodicaly checks if the brightness has changed and if so, uses the ACPI methods to enact that change.

To use it, you need a PNLF patch (to enable brightness handling in macOS) as well as a patch for you screen to be hooked to GenericBrightness. This is explained below.

Credit: com.ivik.driver.GenericBrightness

The original kext was retrieved from https://github.com/chris1111/GenericBrightness/ but seems to have an older history.

Differences between the older version and this one are minimal. The xcode project has been updated for the latest version of xcode. A bug (linked to an uninitialized variable) causing a KP on Mojave 10.14.4 has been corrected.

Licensing information

The original code does not have a licence... But the code is still freely available online and not distributed by the original author (as far as I can tell). The only change I made is a variable initialization, so I'm giving it away. As the code is fairly simple, I don't think anyone is keeping it a secret and I am redistributing it also.

Installation

Binaries

You can either compile using Xcode 10.2 or download directly binary releases at: https://github.com/christophcharles/GenericBrightness/releases .

Configuration

The full explanation is still available at: https://www.insanelymac.com/forum/topic/236835-updated-2012-genericbrightnesskext/

Here is a quick reminder though:

• First, you need to add a PNLF device to your DSDT. This is quite straightfoward and can be done in the following way:

Device (PNLF)
{
    Name (_HID, EisaId ("APP0002"))
    Name (_CID, "backlight")
    Name (_UID, 0x0A)
    Name (_STA, 0x0B)
}

• Then, you need to mark your screen. Find you GPU node. It is usually something like _SB.PCI0.GFX0 or if you renamed it to IGPU _SB.PCI0.IGPU. Under this node, you will find something like LCD, CRT or TV. In my case, it was for instance _SB.PCI0.IGPU.LCD0. The device must have the following methods :
  • _BCM
  • _BCQ
  • _BCL If you have found it, at the line: Name (_HID, EisaId ("LCD1234")). This leads to something like:

Device (LCD)
{
    Name (_ADR, 0x0400)
    Name (_HID, EisaId ("LCD1234")) //this must be added
    Method (_DCS, 0, NotSerialized)
    {
    }
    Method (_DGS, 0, NotSerialized)
    {
    }
    Method (_BCL, 0, NotSerialized)
    {
    }
    Method (_BCM, 1, NotSerialized)
    {
    }
    Method (_BQC, 0, NotSerialized)
    {
    }
}

Once all this is done, put GenericBrightness.kext in /Library/Extensions/, put the correct permissions :

$ chown -R root:wheel GenericBrightness.kext
$ chmod -R 755 GenericBrightness.kext

And rebuild the kernel cache:

$ kextcache -i /

On reboot, brightness should work.

Troubleshooting

This was only testing on one computer and only with Mojave 10.14.4. Your mileage may vary.

If your brightness keys on your keyboard do not work, this is not related to this kext. Try to use the slider in system preferences to check if the kext work. For the keyboard keys, check: https://www.tonymacx86.com/threads/guide-patching-dsdt-ssdt-for-laptop-backlight-control.152659/ . The part for keyboard control is still applicable on Mojave.

If the slider does not work in system preferences, there is a huge chance that the OEM ACPI methods do not work. You should try using a patched AppleBacklight kext.