Phase II.X.W: extend the acpid main loop to handle the
kstop reason 3 (S3 wake) with the standard AML sequence
\\_SST(2) -> \\_WAK(3) -> \\_SST(1).
Also adds \`kstop_enter_s3()\` to AcpiScheme: writes the
kernel's S3 resume trampoline address to FACS via the new
SetS3WakingVector AcPiVerb (verb 5). A zero payload is a
sentinel for 'use the kernel's default trampoline address'.
The acpid's enter_sleep_state for S3 will:
1. Do the AML prep (\\_TTS(3), \\_PTS(3), \\_SST(3)) - the
existing set_global_s_state path.
2. Call kstop_enter_s3(0) to write the trampoline
address to FACS.
3. Write 's3' to /scheme/sys/kstop to trigger the
kernel's S3 entry path.
Hardware-agnostic: works on any x86_64 system with
standard ACPI S3 support (Dell, HP, Lenovo, LG Gram 14).
On Modern Standby-only systems (LG Gram 16 (2025)), the
kernel never enters S3 so the S3 wake path is never
executed.
Red Bear OS
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