Battery, AC, lid, and the power button ride the acpi service as reported
children with small class drivers — the xHCI split repeated. QEMU can
only prove the power-button path (system_powerdown injects the real fixed
event), so battery/EC are interface-complete and hardware-validated on
the laptop. Per-device power states (D-states, suspend/resume) stay out
of scope: suspend has the shape of a lifecycle signal every driver must
answer, and it has no consumer until laptop sleep.
Daniel Samson