I've created a new program, with a silly name, that solves a silly problem with devicetree overlays. Seem that, alhough there's patches to fully support overlays, including loading them on the fly into a running system, it's not in the mainline kernel, and nobody seems to know if/when it will get mainlined.

So easy-peasy-devicetree-squeezy is a hack to make it easy to do device tree overlay type things already. This program makes it easy peasy to squeeze together the devicetree for your board with whatever additions you need. It's pre-deprecated on release; as soon as device tree overlay support lands, there will be no further need for it, probably.

It doesn't actually use overlays, instead it arranges to include the kernel's devicetree file for your board together with whatever additions you need. The only real downside of this approach is that the kernel source tarball is needed. Benefits include being able to refer to any labels you need from the kernel's devicetree files, and being able to #include and use symbols like GPIO_ACTIVE_HIGH from the kernel headers.

It supports integrating into a Debian system so that the devicetree will be updated, with your additions, whenever the kernel is upgraded.

Source is in a git repository at https://git.joeyh.name/index.cgi/easy-peasy-devicetree-squeezy.git/
See the README for details.

If someone wants to package this up and include it in Debian, it's a simple shell script, so it should take about 10 minutes.

example use

Earlier I wrote about cubietruck temperature sensor setup, and the difficulty I had with modifying the device tree for that. With easy-peasy-devicetree-squeezy, I only have to create a file /etc/easy-peasy-devicetree-squeezy/my.dts that contains this:

    /* Device tree addition enabling onewire sensors
     * on CubieTruck GPIO pin PG8 */
    #include <dt-bindings/gpio/gpio.h>

    / {
            onewire_device {
                    compatible = "w1-gpio";
                    gpios = <&pio 6 8 GPIO_ACTIVE_HIGH>; /* PG8 */
                    pinctrl-names = "default";
                    pinctrl-0 = <&my_w1_pin>;

    &pio {
            my_w1_pin: my_w1_pin@0 {
                    allwinner,pins = "PG8";
                    allwinner,function = "gpio_in";

Then run "sudo easy-peasy-devicetree-squeezy --debian sun7i-a20-cubietruck"

Today's work was sponsored by Trenton Cronholm on Patreon.