Workstations support with variable dGPU : SeaBIOS chainloading of Heads needed?

Nobody has claimed this yet.

- coreboot oprom pci extraction + loading exists, but is not providing VBIOS: SeaBIOS does.
- coreboot/SeaBIOS seperation of duties prohibit coreboot by ideology from providing VBIOS implementation: SeaBIOS does and is said to do it well.
- SeaBIOS does more then extract oprom from PCI+loads it, it implements VBIOS dGPU implementation for which oprom IRQ polling results in functional graphic handling.
- Without VBIOS implementation in firmware provided by SeaBIOS (free or proprietary), oprom alone gives variable dGPU support.
- So Hypothesis here is that SeaBIOS should be used to chainload Heads payload instead of trying to implement VBIOS+oprom loading inside of coreboot. But to do so well, SeaBIOS should hebable TPM measured boot and read oprom in ram, measure it, extend TPM PCR and then load oprom+offer VBIOS free implementation so IRQ polling is functions.

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Traces of discussions (only accessible by current members of D16 club):
- Discussion happened under https://matrix.to/#/!OkpUfvLEYpLyALVvaW:dodoid.com/$Oeai4eu3okikozVksCyW-4ML2DghNBr2fYI9oBcuV5c?via=dodoid.com&via=matrix.org&via=envs.net
- Failed previous PoC resulted by a Kconfig setting missing, this one: https://matrix.to/#/!OkpUfvLEYpLyALVvaW:dodoid.com/$jg0G2adlj6WKaGvjiE-egCqCjmL7AyDqRLBTl6tdxds?via=dodoid.com&via=matrix.org&via=envs.net
- Some failed resulting experiments branches to be revisited in next PoC iteration
- https://github.com/tlaurion/heads/tree/coreboot-411_d16_dgpu_oprom_test
- https://github.com/tlaurion/heads/tree/d16_kernel_618_coreboot_fam15h-oprom

_Originally posted by @tlaurion in https://github.com/linuxboot/heads/issues/1792#issuecomment-2435808059_

Review the referenced coreboot-411_d16_dgpu_oprom_test and d16_kernel_618_coreboot_fam15h-oprom branches, along with the reported missing Kconfig setting and linked discussion traces. Determine whether a new PoC can chainload the Heads payload through SeaBIOS while measuring the dGPU option ROM; done would require a reproducible workstation test with functional variable-dGPU handling.

Written by the indexing model from the issue text.