Hi,
I´m currently getting more and more into the Device Tree and I have a basic overview how it works and how DTOs are written. I wrote an overlay to enable a GPIO as output. The Pinmux fragment works but I am not sure what is the “bone-pinmux-helper” (here in fragment@1) for. Some overlays I reviewed have this fragment and some not. So I´m not sure what it is doing and if I need this.
I created an little overlay here with this device tree overlay generator (http://www.kilobaser.com/blog/2014-07-28-beaglebone-black-devicetreeoverlay-generator) and commented my thoughts and question in blue.
/dts-v1/;
/plugin/;
/{
compatible = “ti,beaglebone”, “ti,beaglebone-black”;
part_number = “BS_PINMODE_P8_26_0xf”;
exclusive-use =
“P8.26”,
“gpio1_29”;
fragment@0 {
target = <&am33xx_pinmux>;
overlay {
bs_pinmode_P8_26_0xf: pinmux_bs_pinmode_P8_26_0xf {
pinctrl-single,pins = <0x07c 0xf>;
};
};
};
fragment@1 {
target = <&ocp>; //targets the on-chip-peripherials (ocp) node in the Device Tree
overlay {
bs_pinmode_P8_26_0xf_pinmux { //creates a subnode with the name “bs_pinmode_P8_26_0xf_pinmux”
compatible = “bone-pinmux-helper”; //what is the “bone-pinmux-helper” and where can i find more documentation on that?
status = “okay”; //what is actiaved here?
pinctrl-names = “default”;
pinctrl-0 = <&bs_pinmode_P8_26_0xf>; //refering to pincontroll settings from bs_pinmode_P8_26_0xf in fragment@0
};
};
};
};
I want to drive an Enable Input of a display with that GPIO (don´t confuse with DE-Mode) which is active high. So my idea is that the display will be enabled when the DTO will be loaded through the cape manager. Is there a way to set 1 as a default value in the overlay for that output pin? (DTO is loaded > value is instantly 1?)
Cheers