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I found this document.
It says:

Open Drain and Open Source

Sometimes shared signals need to use "open drain" (where only the low signal level is actually driven), or "open source" (where only the high signal level is driven) signaling. That term applies to CMOS transistors; "open collector" is used for TTL. A pullup or pulldown resistor causes the high or low signal level. This is sometimes called a "wire-AND"; or more practically, from the negative logic (low=true) perspective this is a "wire-OR".

I understand what the setting causes while using the pin as output but I don't understand what differences it causes while using the pin as input. (I can set any input pin to open drain or open source. gpioinfo gpiochip0 shows me that it's set.)

I am using #include <linux/gpio.h> to interact with the gpio pins. What exactly does the GPIOHANDLE_REQUEST_INPUT do? Is the pin in a tri state is it sinking and what does the open source open drain setting do on inputs?

Findings: I found out that input open drain is the same as output open drain low.

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