Understanding Device Trees
How a device tree describes UARTs, I2C, SPI, GPIO, regulators and interrupts to the kernel, and what Yocto deploys with it.
Device Tree
The Linux kernel cannot simply assume that every ARM board contains the same hardware.
The device tree describes hardware to the kernel.
For example, it can describe:
- UART
- Ethernet
- I²C
- SPI
- GPIO
- MMC
- USB
- Display
- Regulators
- Interrupts
A simplified device-tree fragment might look like:
uart1 {
compatible = "vendor,uart";
status = "okay";
};
The exact syntax and hardware definitions depend on the processor and board.
Yocto can build and deploy the appropriate device-tree files together with the kernel.