overlays

Additional device tree overlays to support different hardware on Radxa products

This repo is supposed to be applied directly over Linux source tree. You will also need this patch so they can be built with the kernel.

Metadata specs

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

B. Compatible (array)

1. compatible should not be a SoC unless it is truly compatible for every products using that SoC.
   rsetup will match base device tree's compatible with overlay's compatible. As long as one value from each matches, the overlay is considered compatible. Since most product's device tree contains their SoC in compatible, setting SoC in overlay's compatible will make it compatible with every such products.
   Explicit products list should be perferred 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 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 ending period.
2. New line in description should use \n.
3. Hardware parameters should be listed at the end to help user to connect their devices.