Device Tree overlays for sunxi devices running Armbian images with mainline kernel
As of now overlays in this repository should work with the kernel version 4.14.x. They may need changes/adjustments to work on older versions and eventually they will be updated to newer kernel versions.
CONFIG_OF_LIBFDT_OVERLAY
enabledoverlay_prefix
valueNotes:
fdt get value
commandBoot script reads /boot/armbianEnv.txt
which may contain following environment variables:
overlay_prefix
overlays
user_overlays
Overlay files referenced by overlays
and user_overlays
variables are loaded and applied using fdt apply
command. After applying all overlays a SoC specific fixup script is executed to process overlay specific parameters.
fdt
command does not support "tuples" values which limits implementing things like GPIO SPI chip selects with variable GPIO pins that require this type of values:cs-gpios = <0>, <&pio 0 1 0>, <&pio 7 7 0>; /* Native, PA1, PH7 */
U-boot does not support overlay parameters, so changing values is implemented via executing a "fixup" script after all overlays were applied. This script uses environment variables loaded from /boot/armbianEnv.txt
to change the live tree using fdt
command.
Since SoCs have multiple controllers of the same type (I2C, SPI) that can be exposed in different combinations on different boards, slave devices (I2C, I2S, SPI, ...) are provided not as ready to use overlays but as examples that require minimal editing to match the used configuration.