How do Kext work??

[lzamir]

Hi,

I'm new to the concept of Kext and I try to understand some basic things about it and I don't seem to find the answers. Can you please help?
I understand that Kext are like drivers in windows. However, who decides which Kext the device (let's say audio) will use while loading? I can have multiple audio kext, what mechanism/file/config, determines which one to load?? I looked everywhere for some pointer like file that says for audio load kext <kext name>. isn't this the way it works??

Your explanation is appreciated!

Regards,

Lior.

 

[Flym4n]

You should only have 1 audio kext or DSDT enabler, ...

Best solution vary from chip to chip.
Apple uses 889a, and DSDT patching is enough to get it working
for 88x, you should use DSDT & patched applehda OR HDAEnabler & LegacyHDA.

VoodooHDA is another solution, an on-the-fly patching-injecting of/in applehda. It's the easier solution, but do not work for everything like mic, 7.1 output, ...

 

[lzamir]

Thanks for the answer but Audio was just an example.
My question is, how does the system knows which kext to use for a certain device?
I presume that there are many kext for screen or graphics for example. How does the system determines which one to use? Or is it the other way around, the device looks for a proper kext in the 'Extension' directory.

Lior.

 

[mozo]

Kernel extension's info.plist describes how it should be loaded. There is many matching categories kexts using, from device-id to specific "name" or description entry in the registry what's injecting by EFI drivers (or any other injectors) or with DSDT's _DSM method.