unable to export a gpio pin

Question

I am trying to export a pin (no. 110) using the following in linux:
echo 110 > /sys/class/gpio/export

When I try to do so, I getthe error message
ash: write error: Device or resource busy

As per my knowledge the pin is not being used by any module, but I may be wrong. I had the hardware line probed and the voltage is changing, the processor seems to be driving something to the line.
The pin according to the user manual is not multiplexed and is "commonly available".

Answer 1

The pin according to the user manual is not multiplexed and is "commonly available".

Apparently you are referring to a SoC manual.
Such a statement will only imply that the pin does not have a dedicated application by an integrated peripheral (as shipped by the SoC manufacturer).
That statement is invalidated when the SoC is designed into a circuit and/or installed on a board.

The document that you really need to consult is the board manual or the board schematics.
That should be the accurate documentation as to how the board designer used the available GPIO pins in that specific application.

When I try to do so, I getthe error message ...

Fortunately for you, the device driver that does use that pin (that you want to use) has properly performed the GPIO reserve/request call to prevent a hijack.
This prevented that other driver from breaking and/or a device/board malfunction.

As per my knowledge the pin is not being used by any module, but I may be wrong

How did you attain this "knowledge"?
Did you scan the .dts and .dtsi files used for your board?
Did you check the source code of every device driver used by your board?