overlays

Additional device tree overlays to support different hardware on Radxa products

Build overlays in-tree

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

The official overlays are built in-tree, and is delivered as part of the kernel package.

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 -j$(nproc)

Please be aware this only build a subset of overlays, and any overlays that depend on vendor headers will fail. This is because the Makefile is intended to find overlays that are incompatible with upstream kernel.

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 indvidual run.

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

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 after:

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

A. Title (string)

1. title should not contain the product name.
   rsetup will only show compatible overlays with compatible field. 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. Compatible (array)

1. compatible should not be an SoC unless it is truly compatible with every products 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 a overlay is broken, compatible should be unknown.

C. Category (string)

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

D. 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.

E. 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 user to connect their devices.