OpenSBI provides firmware builds for specific platforms. Different types of firmwares are supported to deal with the differences between different platforms early boot stage. All firmwares will execute the same initialization procedure of the platform hardware according to the platform specific code as well as OpenSBI generic library code. The supported firmwares types will differ in how the arguments passed by the platform early boot stage are handled, as well as how the boot stage following the firmware will be handled and executed.
OpenSBI currently supports two different types of firmwares.
The FW_JUMP firmware only handles the address of the next booting stage entry, e.g. a bootloader or an OS kernel, without directly including the binary code for this next stage.
A FW_JUMP firmware is particularly useful when the booting stage executed prior to OpenSBI firmware is capable of loading both the OpenSBI firmware and the booting stage binary to follow OpenSBI firmware.
The FW_PAYLOAD firmware directly includes the binary code for the booting stage to follow OpenSBI firmware execution. Typically, this payload will be a bootloader or an OS kernel.
A FW_PAYLOAD firmware is particularly useful when the booting stage executed prior to OpenSBI firmware is not capable of loading both OpenSBI firmware and the booting stage to follow OpenSBI firmware.
A FW_PAYLOAD firmware is also useful for cases where the booting stage prior to OpenSBI firmware does not pass a flattened device tree (FDT file). In such case, a FW_PAYLOAD firmware allows embedding a flattened device tree in the .text section of the final firmware.
All firmware types mandate the definition of the following compile time configuration parameter.
Additionally, each firmware type as a set of type specific configuration parameters. Detailed information for each firmware type can be found in the following documents.