sp1: acpi: Add ACPI init groundwork

Signed-off-by: Ian Moffett <ian@mirocom.org>

usr/src/sp1/common/io/acpi/acpi_init.c

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2026, Mirocom Laboratories
+ * All rights reserved.
+ *
+ * The following sources are CONFIDENTIAL and PROPRIETARY
+ * property of Mirocom Laboratories. Unauthorized copying,
+ * use, distrubution or modification of this file, in whole
+ * and in part, is strictly prohibited without the prior written
+ * consent from Mirocom Laboratories.
+ */
+
+#include <io/acpi/acpi.h>
+#include <io/acpi/tables.h>
+#include <lib/printf.h>
+#include <os/knot.h>
+#include <os/bpt.h>
+#include <mm/vm.h>
+
+#define pr_trace(fmt, ...) \
+    printf("acpi: " fmt, ##__VA_ARGS__)
+
+static struct acpi_rsdp *rsdp = NULL;
+static struct acpi_root_sdt *root_sdt = NULL;
+static size_t root_sdt_entries = 0;
+
+/*
+ * Verify the RSDP structure
+ */
+static void
+rsdp_verify(void)
+{
+    uint8_t major;
+    uint8_t csum = 0;
+
+    /*
+     * Some implementations like those found in emulators may
+     * have their revision set to zero alongside ACPI 1.0 behavior.
+     * If we encounter a zeroed revision, just bump it up by one.
+     */
+    if ((major = rsdp->revision) == 0) {
+        ++major;
+    }
+
+    /* Print the version and compute checksum */
+    pr_trace("detected acpi %d.0 by %.6s\n", major, rsdp->oemid);
+    for (size_t i = 0; i < rsdp->length; ++i) {
+        csum += ((uint8_t *)rsdp)[i];
+    }
+
+    /* Is the checksum valid? */
+    if ((csum & 0xFF) != 0) {
+        knot("bad checksum %x for acpi rsdp\n", csum);
+    }
+}
+
+void
+acpi_init(void)
+{
+    struct bpt_protovar pv;
+    status_t status;
+    struct acpi_header *hdr;
+    uintptr_t pma;
+
+    status = bpt_get_protovar(&pv);
+    if (status != STATUS_SUCCESS) {
+        knot("could not obtain protovar\n");
+    }
+
+    rsdp = pv.rsdp;
+    rsdp_verify();
+
+    /* Select the correct root sdt */
+    if (rsdp->revision < 2) {
+        pr_trace("using rsdt as root sdt\n");
+        root_sdt = pma_to_vma((uintptr_t)rsdp->rsdt_addr);
+        root_sdt_entries = (root_sdt->hdr.length - sizeof(root_sdt->hdr)) / 4;
+    } else {
+        pr_trace("using xsdt as root sdt\n");
+        root_sdt = pma_to_vma((uintptr_t)rsdp->xsdt_addr);
+        root_sdt_entries = (root_sdt->hdr.length - sizeof(root_sdt->hdr)) / 8;
+    }
+}

usr/src/sp1/common/os/main.c

@@ -10,6 +10,7 @@
  */
 
 #include <io/cons/cons.h>
+#include <io/acpi/acpi.h>
 #include <os/bpt.h>
 #include <os/knot.h>
 #include <lib/printf.h>
@@ -56,6 +57,9 @@ main(void)
     /* Initialize virtual memory management */
     mm_vm_init();
 
+    /* Initialize ACPI */
+    acpi_init();
+
     printf("[*] sp1 is pre-alpha\n");
     printf("[*] knotting kernel...\n");
     knot("end of kernel reached - halting\n");

usr/src/sp1/head/io/acpi/acpi.h

@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2026, Mirocom Laboratories
+ * All rights reserved.
+ *
+ * The following sources are CONFIDENTIAL and PROPRIETARY
+ * property of Mirocom Laboratories. Unauthorized copying,
+ * use, distrubution or modification of this file, in whole
+ * and in part, is strictly prohibited without the prior written
+ * consent from Mirocom Laboratories.
+ */
+
+#ifndef _ACPI_ACPI_H_
+#define _ACPI_ACPI_H_ 1
+
+/*
+ * Initialize ACPI, panics on failure
+ */
+void acpi_init(void);
+
+#endif  /* !_ACPI_ACPI_H_ */