From Armbian documentation (https://docs.armbian.com/User-Guide_Allwinner_overlays/)
Most in-circuit and GPIO based interfaces (SPI, I2C, I2S, …) don’t have a mechanism for detecting and identifying devices connected to the bus, so Linux kernel has to be told explicitly about the device and its configuration details.
While Device Tree is a way of describing hardware configuration to the kernel, Device Tree overlays are a way for modifying the DT in order to provide the kernel and kernel drivers with details about external devices or to activate interfaces disabled by default.
What do we want?
We want to add Device Tree overlays for the onboard interfaces and tested external devices so that they appear in future mainline Armbian images. This means that activating this type of hardware will not require recompiling the Device Tree or will require compiling just the overlay file which will be compatible with future kernel updates.
What kind of help do we expect?
We want people to participate in making and testing overlays for the hardware that they have.
Participation requirements:
An A10, A20 or H3 board that can boot the current mainline kernel
Serial console adapter for getting the u-boot logs if they are needed
Extra SD card to use for booting the nightly/beta images
I2C, SPI or I2S (only A10 and A20 based boards since I2S driver is not present on H3 yet) device that you can connect to the board and that requires either generic driver (like SPIdev) or a special driver (available in the mainline kernel), with an exception of custom built boards that don't have commercially available compatible alternatives and devices that don't have in-tree kernel drivers.
Some generic Linux knowledge (i.e. how to obtain a dmesg log, how to check file contents)
At least a basic understanding of the hardware that you have and how does it integrate into Linux. For example I have no idea how to calibrate a resistive touch screen even if I can write a DT overlay for it.
Please note that some hardware limitations (i.e. number of SPI chip selects, missing SPI DMA support) may affect possibility of supporting some devices
What overlays are already available?
Please check the README in the subdirectory for your SoC in the overlays repository: https://github.com/zador-blood-stained/sunxi-DT-overlays-armbian
From Armbian documentation (https://docs.armbian.com/User-Guide_Allwinner_overlays/) Most in-circuit and GPIO based interfaces (SPI, I2C, I2S, …) don’t have a mechanism for detecting and identifying devices connected to the bus, so Linux kernel has to be told explicitly about the device and its configuration details. While Device Tree is a way of describing hardware configuration to the kernel, Device Tree overlays are a way for modifying the DT in order to provide the kernel and kernel drivers with details about external devices or to activate interfaces disabled by default. What do we want? We want to add Device Tree overlays for the onboard interfaces and tested external devices so that they appear in future mainline Armbian images. This means that activating this type of hardware will not require recompiling the Device Tree or will require compiling just the overlay file which will be compatible with future kernel updates. What kind of help do we expect? We want people to participate in making and testing overlays for the hardware that they have. Participation requirements: An A10, A20 or H3 board that can boot the current mainline kernel Serial console adapter for getting the u-boot logs if they are needed Extra SD card to use for booting the nightly/beta images I2C, SPI or I2S (only A10 and A20 based boards since I2S driver is not present on H3 yet) device that you can connect to the board and that requires either generic driver (like SPIdev) or a special driver (available in the mainline kernel), with an exception of custom built boards that don't have commercially available compatible alternatives and devices that don't have in-tree kernel drivers. Some generic Linux knowledge (i.e. how to obtain a dmesg log, how to check file contents) At least a basic understanding of the hardware that you have and how does it integrate into Linux. For example I have no idea how to calibrate a resistive touch screen even if I can write a DT overlay for it. Please note that some hardware limitations (i.e. number of SPI chip selects, missing SPI DMA support) may affect possibility of supporting some devices What overlays are already available? Please check the README in the subdirectory for your SoC in the overlays repository: https://github.com/zador-blood-stained/sunxi-DT-overlays-armbian