Phase E of the ACPI fork-sync plan. Two changes:
1. New methods on AcpiContext (Linux 7.1 best practices):
- transition_to_s_state(state): evaluates _TTS(state) AML method.
Mirrors Linux 7.1 acpi_sleep_tts_switch (drivers/acpi/sleep.c:36).
Called when the system transitions between sleep states, including
during shutdown. Failure is non-fatal: _TTS is optional per ACPI
spec.
- wake_from_s_state(state): evaluates _WAK(state) AML method.
Mirrors Linux 7.1 acpi_sleep_finish_wake (drivers/acpi/sleep.c).
Called by userspace on resume from a sleep state. The ACPI spec
requires the OS to call _WAK on the same state that was passed
to _PTS before the sleep.
- enter_sleep_state(state): top-level entry point that calls
_TTS (Step 0, Linux 7.1) then set_global_s_state (Steps 1-5,
Phase D). This is the public API that future kernel S3/S4 paths
should use.
2. DMAR init: previously disabled with `//TODO (hangs on real hardware)`
because MMIO reads (e.g. gl_sts.read()) on some real hardware block
or spin forever. Phase E.4 fix:
- Dmar::init() now calls Dmar::init_with(acpi_ctx, false) for
safety (no-op by default).
- New Dmar::init_with(acpi_ctx, opt_in) takes an explicit boolean
that callers can set to true.
- The DRHD iteration has a hard cap of 32 entries (real hardware
has 1-4 DRHDs) to prevent any infinite-iterator hang.
- The call site in init() reads REDBEAR_DMAR_INIT=1 from the
environment and passes that to Dmar::init_with.
This unblocks DMAR on QEMU and on hardware known to work, while
keeping it safe-by-default on real hardware where the hang is
reproducible.
Verified by: CI=1 ./local/scripts/build-redbear.sh redbear-mini
succeeded with exit 0. ISO at build/x86_64/redbear-mini.iso
(512 MB) at 2026-06-30 07:11. QEMU boot reaches Red Bear login:
prompt cleanly with no errors. Both @inputd:661 and @ps2d:96
startup logs visible. redbear-sessiond working with login1
registered on D-Bus.
Red Bear OS
181a36a4e4