add device platform module with ACPI support

src/device/platform.zig

@@ -0,0 +1,67 @@
+//! The firmware-agnostic discovery facade.
+//!
+//! The kernel calls `platform.discover()` and gets back a generic `DeviceTree`
+//! without ever naming ACPI or device-tree — the same way it imports `arch`
+//! without naming x86_64. Which backend runs is decided *at runtime* from what
+//! the bootloader handed us (an ACPI RSDP today, a device-tree blob later),
+//! because a single image — a future ARM kernel especially — may boot under
+//! either firmware. That's a deliberate divergence from `arch`, which is a
+//! compile-time choice.
+
+const std = @import("std");
+const danos = @import("danos");
+const device = @import("device.zig");
+const acpi = @import("acpi.zig");
+const power = @import("power.zig");
+const devicetree = @import("devicetree.zig");
+
+pub const DeviceTree = device.DeviceTree;
+pub const Device = device.Device;
+pub const DeviceClass = device.DeviceClass;
+pub const Hal = device.Hal;
+pub const PowerInfo = acpi.PowerInfo;
+pub const AmlStats = acpi.AmlStats;
+
+/// The register map + sleep types discovery extracted, for logging/diagnostics.
+pub fn powerInfo() PowerInfo {
+    return acpi.power_info;
+}
+
+/// AML parse integrity/diagnostics (namespace node count, bytes consumed).
+pub fn amlStats() AmlStats {
+    return acpi.aml_stats;
+}
+
+/// Enumerate hardware into a fresh device tree. `hal` supplies the hardware
+/// primitives the backend needs (MMIO mapping for PCIe config space, port I/O for
+/// ACPI registers); pass the arch implementation. Errors leave nothing to clean up
+/// beyond the tree's own allocations.
+pub fn discover(
+    boot_info: *const danos.BootInfo,
+    allocator: std.mem.Allocator,
+    hal: Hal,
+) !DeviceTree {
+    var dt = try DeviceTree.init(allocator);
+
+    if (boot_info.acpi_rsdp != 0) {
+        try acpi.discover(boot_info.acpi_rsdp, &dt, hal);
+    } else {
+        // No ACPI RSDP. A device-tree boot would parse its blob here; today that
+        // path is a stub, so this reports the machine described itself no way we
+        // understand yet.
+        try devicetree.discover(&dt);
+    }
+
+    return dt;
+}
+
+/// Restart the machine. Never returns on success; returns only if no reset method
+/// worked (extremely unlikely). Backend-agnostic entry the kernel calls.
+pub fn reboot(hal: Hal) void {
+    power.reboot(hal);
+}
+
+/// Power the machine off (ACPI S5). Never returns on success.
+pub fn shutdown(hal: Hal) void {
+    power.shutdown(hal);
+}