I am using all available GPIO on the X16 connector on the Iris Carrier Board. I don’t plan to use any audio signals in my application. Is it possible to convert the Iris X8 and X9 connector pins to GPIO via device tree modification or other means? If yes, please advise.
No, it is not possible to use the audio pins as GPIO.
The touch and analogue input pins however (X19 and X16) could be used as GPIO.
Touch and analogue is implemented with an STMPE811.
You would need to configure the the gpio driver for the chip and change the device tree accordingly.