Hello, I'm currently taking a look at modifying the bayou payload in order to make it work on a modern coreboot system.
The conversion seems pretty straightforward except for a few points that I'm unsure about since I don't know what the situation was during the coreboot-v3/LAR era or what was the payload's design process like.

1) Bayou is currently designed this way:

• Take user-written xml configuration
• Use pbuilder utility to parse the config
• pbuilder then generates a single blob containing every payload specified (it also performs elf->self conversions, adds the payloads to the blob, etc.)
  
• Bayou (when executed) takes a compressed blob
• Reads the configuration from it
  
• Parses through the blob looking for each payload specified
  
• Follows the rest of the configuration
  

This design choice seems a bit inappropriate given that we are nowadays used to store multiple secondary payloads directly inside the cbfs (with the re-introduction of bayou "secondary payloads" could also be expanded to contain all the payloads).

I'm instead thinking of doing the following changes:

• Doing away with the blob
• Storing the configuration inside the cbfs as a cbfs_file
• Parse the configuration directly from the cbfs
• Use cbfstool to handle all addition/removal of payloads to the cbfs
• Eliminate pbuilder
  

This seems to be a much cleaner solution than the current one.
I currently don't see any downsides to it but I would like to hear other opinions on the matter.