feat: power down dGPUs on hybrid graphics laptops

kernel/src/ACPI/AcpiPower.hpp

@@ -0,0 +1,92 @@
+/*
+    * AcpiPower.hpp
+    * ACPI device power management: _PSx methods, _PRx power resources,
+    * _DSM calls, and finding the namespace node behind a PCI function
+    * Copyright (c) 2026 Daniel Hammer
+*/
+
+#pragma once
+#include <cstdint>
+#include <ACPI/AML/AmlNamespace.hpp>
+
+namespace Hal {
+    namespace AcpiPower {
+
+        // ============================================================================
+
+        // PCI <-> ACPI
+
+        // ============================================================================
+        // The Device node describing PCI function bus:dev.fn, or -1. When
+        // firmware declares more than one node at the same address (a generic
+        // placeholder plus a vendor SSDT's real one is common for GPUs), the
+        // one carrying power-management objects wins.
+        int32_t FindPciDevice(uint8_t bus, uint8_t dev, uint8_t fn);
+
+        // Forget the PCI address map built by FindPciDevice (bus numbers may
+        // change across a resume).
+        void InvalidatePciMap();
+
+        // True when `device` has a child object named `name` ("_PS3").
+        bool HasObject(int32_t device, const char* name);
+
+        // ============================================================================
+
+        // Power resources
+
+        // ============================================================================
+        static constexpr int MaxResources = 8;
+
+        // The power resources the device lists in _PR0.._PR3 (deduplicated).
+        int CollectResources(int32_t device, int32_t* out, int max);
+
+        // _STA of a power resource: 1 on, 0 off, -1 unknown.
+        int ResourceState(int32_t resource);
+
+        // ============================================================================
+
+        // Device power transitions
+
+        // ============================================================================
+        struct D3ColdReport {
+            bool RanPs3;
+            int  ResourcesOff;      // resources whose _OFF was run
+            int  ResourcesShared;   // left on: some other present device needs them
+            int  ResourcesStillOn;  // _OFF ran but _STA still says on
+        };
+
+        // Put an ACPI device into D3cold the way the spec orders it: _PS3,
+        // then every power resource it depends on off, last-listed first. A
+        // resource that a device outside `owners` also depends on is left
+        // on -- `owners` lists the nodes being powered down together (the
+        // functions of one card and the port above them), which may freely
+        // share, as may anything below them in the namespace. The PCI side
+        // (PMCSR to D3hot) is the caller's to do first.
+        void EnterD3Cold(int32_t device, const int32_t* owners, int ownerCount,
+                         D3ColdReport& report);
+
+        // ============================================================================
+
+        // _DSM
+
+        // ============================================================================
+        // Evaluate _DSM(uuid, revision, function, arg3) on a device. False
+        // when the device has no _DSM or it failed.
+        bool EvaluateDsm(int32_t device, const uint8_t uuid[16], uint64_t revision,
+                         uint64_t function, const AML::Object& arg3, AML::Object& result);
+
+        // The function bitmap _DSM function 0 reports for (uuid, revision),
+        // 0 when unsupported. Bit 0 set means "some functions exist".
+        uint64_t DsmFunctions(int32_t device, const uint8_t uuid[16], uint64_t revision,
+                              const AML::Object& arg3);
+
+        // Helpers for building _DSM / method arguments.
+        AML::Object IntegerArg(uint64_t value);
+        AML::Object BufferArg(const uint8_t* bytes, uint32_t length);
+        AML::Object EmptyPackageArg();
+
+        // Integer value of a method result: an integer as is, a buffer read
+        // little-endian (up to 8 bytes).
+        uint64_t ResultInteger(const AML::Object& result);
+    };
+};