I want to use GPIO pins on i.MX6 UltraLite EVK (both inputs and outputs). I think, some GPIOs are physically accessible on J1706 header. But I don't know how to access them from Linux. I compiled the OS using Yocto (core-image-base). How can I configure GPIOs on J1706 header to be output or input and then write value to the pin or read the value from the pin? Do I have to modify device tree?