Based on imx6ulevk EVK, I would like to write a helloworld GPIO module for char driver, and think the ON/OFF hardware button on board can be a reference design.
From schema and pin tool, I see that ON/OFF button is on R8 pin, peripheral is System Reset Controllor(SRC) , with src.RESET_B in IOMUX
However, where is the source code for this driver? I tried various of searching ways, including searching keywords in source, in build directory, and in running board /proc, but none of them had got me there. I had written drivers for linux 2.6 many years ago, but when trying to refresh self and picking things up in yocto + Linux 4.x recently, confusion are confronted more than expected.
Could anyone tell me what is the correct steps to search for its driver? Or... is it a pure hardware button and just power off CPU without any source code..?
Thanks & Regards