How does the PWM signal between a motherboard and display work?

[TrantaLocked]

There are a few characteristics of a PWM signal from high to low like voltage, frequency and duty ratio. However, which of these characteristics are controlled by the motherboard? Is there a handshake that let's the display choose what it wants, or does the motherboard firmware force one set of values regardless of which display is installed? So for example, does the motherboard only control voltage level and the display handles the rest, or does the motherboard also control the frequency of the signal?

[Ishayin]

From the way Notebookcheck reviews are written, I've always been under the impression that the PWM controller is a part of the screen itself:
https://www.notebookcheck.net/Why-Pulse-Width-Modulation-PWM-is-such-a-headache.270240.0.html

 

I had a quick look and found this thread which also seems to support this being the case:
https://forums.tomsguide.com/threads/pwm-is-controlled-by-screen-or-motherboard.431490/