Device Tree entry/setting to control a GPIO on Beagleboard xM?

Is there an easy way to set some arbitrary value to a GPIO output? It seems that on Beagleboard xM the GPIOs are coming up HIGH by default, and we have a buzzer attached to GPIO_137, which is buzzing the heck out of us until the kernel is fully up, and we can switch it off by software. :slight_smile:

I prepended the U-Boot boot command with “gpio clear 137”, which does silence the buzzer for a couple of seconds, then the kernel begins to boot, and the buzzer comes back up (the kernel switches it to 1 on startup?). I assume there must be a way to set the value to a specific register via the DTS?

This is a standard setup of Robert C. Nelson’s Ubuntu demo image.


Were you able to find a solution?
Which Kernel were you using? Anything pre dtb is simply a change in the board config file using a function from mach/gpio.h
I am looking for the same solution for kernel 3.12 using the device tree blob.