Phase I.5: extend acpid to consume the kstop reason codes
the kernel sets on each kstop event (kcall 2 / CheckShutdown
now returns u8: 0=idle, 1=shutdown (S5), 2=s2idle wake,
3=s3 wake).
The acpid main loop now branches on the reason instead of
treating every kstop event as a shutdown:
* 0 (idle) — spurious wake, ignore
* 1 (shutdown) — set_global_s_state(5) and exit
* 2 (s2idle wake) — exit_s2idle() (\_SST(2) -> \_WAK(0) ->
\_SST(1))
* 3 (s3 wake) — Phase II TODO
The kstop_reason() helper calls the kernel AcpiScheme's
CheckShutdown verb (kcall 2) and returns the u8 reason.
Implemented as a method on AcPiScheme that wraps the
handle's call_ro().
The s2idle flow now end-to-end works:
1. acpid: enter_s2idle() (\_TTS(0), \_PTS(0), \_SST(3))
2. acpid: write 's2idle' to /scheme/sys/kstop
3. kernel kstop handler: sets S2IDLE_REQUESTED, returns
4. kernel idle path: mwait_loop() at deepest C-state
5. SCI breaks MWAIT
6. kernel mwait_loop post-handler:
s2idle_request_clear() + s2idle_signal_wake()
(KSTOP_FLAG=2, event signaled)
7. acpid: kstop_reason() returns 2
8. acpid: exit_s2idle() (\_SST(2) -> \_WAK(0) -> \_SST(1))
9. loop back to step 4
Hardware-agnostic: the s2idle state machine is identical
for any platform with Modern Standby (Dell, HP, Lenovo,
LG Gram, etc.). Only the wake source (SCI, GPIO, RTC, ...)
varies per OEM.
The libredox + kcall path uses the upstream redox_syscall
0.8.1's CheckShutdown verb (kcall 2 returns a usize). The
s2idle-specific EnterS2Idle/ExitS2Idle AcPiVerb variants
(Phase J work) are kept in local/sources/syscall/ but
NOT used in this commit because the [patch.crates-io]
chain is not yet wired up (Phase J deferred to avoid the
libredox cross-version type identity issue).
Red Bear OS
76b53f4ec8