README.md

overlays

Additional device tree overlays to support different hardware on Radxa products

Build overlay dkms package

Due to the much more frequent development happening on the overlay compared to the kernel in general, we are once again splitting the overlay into a dedicated package.

However, to guarantee the overlay is compatible with the installed kernel, this package will be delivered as a source code package using dkms, instead of a prebuilt binary package.

You can build the dkms package using the below commands:

sudo apt-get update
sudo apt-get build-dep --no-install-recommends -y .
make all deb

Build overlays in-tree

You will need this patch so this repo can be built with the kernel.

This is how overlays were distributed previously as part of the kernel package. We are still supporting this for older kernels. Newer kernels like Rockchip 6.1 kernel will use the above dkms package instead.

Build overlays locally

First, make sure you have the running kernel header, gcc, and device-tree-compiler installed.

You can then run the following command to build overlays:

make build-dtbo -j$(nproc)

Please be aware this only builds a subset of overlays, and any overlays that depend on vendor headers will fail, as this command will use the current system's kernel header.

Please take a look at the CI workflow to see how to select installed vendor kernel header.

To delete built overlays, run the following command:

make clean

Download prebuilt artifacts

As part of our CI pipeline, the built overlays are uploaded at the end. You can find all CI runs here, and the artifact is located inside each run.

Please be aware that artifacts expire over time, and they are not officially tested versions.

Code style

We mandate reference style for our overlays. Please visit the DTO Syntax page to learn more.

If your existing overlay uses target-path, then the Android documentation does not show a clear migration path. Below is an example of how to convert them:

/{
	fragment@0 {
		target-path = "/";
		__overlay__ {
			some_node: some-node {
				some_prop = "okay";
				...
			};
		};
	};
}

&{/} {
	some_node: some-node {
		some_prop = "okay";
		...
	};
}

Metadata specs

Currently, we mandate a custom metadata node in overlays. This data is parsed by rsetup to provide a human-readable description and conflict detection. Below is a sample metadata node with detailed guidelines:

/ {
	metadata {
		title = "Enable ENC28J60 on SPI2";
		category = "misc";
		compatible = "unknown";
		description = "Enable Microchip ENC28J60 SPI Ethernet controller on SPI2.\nINT=40";
		exclusive = "GPIO2_B3", "GPIO2_B2", "GPIO2_B1", "GPIO2_B4", "GPIO4_A7";
		package = "dkms-enc28j60";
	};
};

A. Title (string)

1. title should not contain the product name.
   rsetup will only show compatible overlays with compatible field defined. As such, do not confuse users to second guess if an overlay is truly compatible when the product name is not explicitly mentioned.
2. title should not end with a period.

B. Category (string)

1. category currently can be one of the following:
   camera, display, misc

C. Compatible (array)

1. compatible should not be an SoC unless it is truly compatible with every product using that SoC.
   rsetup will match the base device tree's compatible with the overlay's compatible. As long as one value from each match, the overlay is considered compatible. Since most products' device tree contains their SoC in compatible, setting SoC in overlay's compatible will make it compatible with every such product.
   Explicit products list should be preferred to generic SoC matching.
2. If an overlay is broken, compatible should be unknown.

D. Description (string)

1. description is a multi-line text to describe the function of the overlay. It can be the same as title with an ending period.
2. Newline in description should use \n.
3. Hardware parameters should be listed at the end to help the user connecting their devices.

E. Exclusive (array)

1. exclusive should refer to the device tree node and property.
2. For features that are muxed to a GPIO line, exclusive should be the GPIO ID.
3. For features that use multiple GPIO lines, they should all be listed under exclusive.
4. For complex overlay, list all GPIO lines used. For exaple, some devices may use GPIO for interrupt, which is also used by another overlay.

F. Package (array)

1. package specify the additional packages to be used with this overlay.
2. When the overlay is disabled, the specified package will NOT be removed.