Jes Klinke has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/46437 )
Change subject: mb/volteer: New variant for Volteer reworked with Dauntless ......................................................................
Patch Set 6:
Patch Set 6: Code-Review+1
I think if you could figure out how to do this using the new REWORK_ID mechanism (b/170385859) being planned instead of creating a new variant, that would be a plus (a device reworked with a dauntless TPM would set a bit indicating it has the "dauntless TPM" rework in the CBI, code can read at runtime and act accordingly). New variants carry extra weight (need Fit images, adds time to builds, etc) that is good to avoid if possible.
I understand. It would be a rather deep branch though. In that the rework affects whether I2C or SPI bus needs to be initialized early in the verstage. And also, currently, coreboot relies on compile time defines to set whether SPI or I2C is used for TPM communication. Implementing a new dispatch layer to be able to switch at runtime sounds far too risky to me.