We defined three real world scenarios which should at least support a high chance that we have covered a lot hardware systems. We categorized the scenarios based on the firmware with levels. With the lowest firmware level it is possible make the whole system stack transparent.
Your hardware runs closed source firmware in legacy CSM mode or the firmware itself is a BIOS. Most systems nowadays already runs UEFI firmware. Please check if the CSM mode in your BIOS settings is enabled if you want to use this scenario.
Execution flow: MBR is executed
Bootloaders: Syslinux, ST provides harddrive image
Requirements: CSM mode or BIOS
Your hardware runs closed source UEFI firmware with the CSM mode disabled in the firmware settings. This mode is currently not support by System Transparency. Feel free to do a pull request and help us out!
Execution flow: GPT, efi partition, UEFI application
Bootloaders: None, stboot can be packed with Linux kernel as EFI application
Requirements: Secure Boot user mode or OEM keys support stboot
Your hardware runs open source firmware. This can be coreboot, TianoCore, slimmbootloader or u-boot. System Transparency has specific firmware requirements. As far we know only coreboot is able to satisfy these requirements. That is why we only support coreboot firmware at the moment.
Execution flow: Payload is executed in firmware
Bootloaders: None, stboot and Linux kernel are part of coreboot payload
Requirements: coreboot capable hardware with 16MB BIOS flash