[TF-A] Getting BUILD_STRING from FIP file

Hi,

Is there a way to get BUILD_STRING (or a similar string / number that uniquely identifies the TF-A build, e.g., BUILD_MESSAGE_TIMESTAMP) from the FIP file?

Basically, I'm trying to find a way to know the build number of a FIP without flashing it.

I've seen that the FIP TOC header has a 32-bit field named 'serial_number'. Can it be used to this end? I'm considering converting BUILD_MESSAGE_TIMESTAMP into an epoch and adding it as 'serial number', but I'm worried that might be an unintended usage of the 'serial_number' field.

Regards, Daniele