U-Boot, vendors and device trees

[orangecms]

U-Boot

Use U-Boot env var to store the DT to choose?

non-EFI

• use DTB directory as per EXTLINUX config
• use DTB per compile time variable CONFIG_DEFAULT_DEVICE_TREE or U-Boot env
• e.g. qcom/sm7150-google-sunfish will expand to
  /foo/qcom/sm7150-google-sunfish.dtb

EFI

• delegate DTB choice down to other bootloader (sd-boot, GRUB)
• pass compat string (?) as EFI variable for DT choice?
• https://lore.kernel.org/u-boot/20231024062032.8543-1-heinrich.schuchardt@canonical.com/
• Support FdtFile EFI variable systemd/systemd#36835

Raspberry PI

One overlay per product, e.g. custom case with screen, carrier board, etc

• https://github.com/raspberrypi/firmware/tree/master/boot/overlays
• https://github.com/raspberrypi/linux/tree/rpi-6.12.y/arch/arm64/boot/dts/broadcom
• https://github.com/torvalds/linux/tree/master/arch/arm64/boot/dts/broadcom
• https://www.raspberrypi.com/documentation/computers/config_txt.html#os_prefix

generic DT

https://lwn.net/Articles/357487/