Getting-Started-With-ACPI/Laptops/trackpad.md

Fixing Trackpads

This SSDT is used to force enable our GPI0 for VoodooI2C to connect onto.

With most modern laptop DSDTs, there's a variable called GPEN or GPHD which are used for setting the status of the GPI0 device. For us, we want to enable the device.

Finding our GPI0

So first things we need to do is find out what variable is used to enable our GPI0 device, lets open up our decompiled SSDT and search for Device (GPI0). Should give you a desult similar to this:

What we care about from this is the _STA method:

Method (_STA, 0, NotSerialized)
{
    If ((GPHD == One))
    {
        Return (0x03)
    }

    Return (0x0F)
}

What we want is for this to always return 0x0F when booting macOS, so we want to make an SSDT that will return GPHD == Zero in macOS.

NOTE that you may have the other way around where GPHD needs to be set as One to return 0x0F. And your device name may also be different, don't throw random SSDTs in thinking it'll work

Once you found the variable and what it should be set to, grab a copy of SSDT-GPI0.dsl and make the required edits. Then clean up with compiling it

More examples

With this example, we can see that we need both SBRG and GPEN to return One. If only one is present, it'll create some issues so in our SSDT we'll want to have both of them return One:

DefinitionBlock("", "SSDT", 2, "ACDT", "GPI0", 0)
{
    External(GPEN, FieldUnitObj)
    External(SBRG, FieldUnitObj)

    Scope (\)
    {
        If (_OSI ("Darwin"))
        {
            GPEN = One
            SBRG = One
        }
    }
}