From c0875764f2a30ea8c9d7f628f2fe0ab2e66589f8 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Mon, 17 Nov 2025 16:48:13 -0500
Subject: kern: acpi: Add acpi_read_madt() helper

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/acpi/acpi.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

(limited to 'sys/acpi')

diff --git a/sys/acpi/acpi.c b/sys/acpi/acpi.c
index f60435b..ac02e5e 100644
--- a/sys/acpi/acpi.c
+++ b/sys/acpi/acpi.c
@@ -28,6 +28,7 @@
  */
 
 #include <sys/cdefs.h>
+#include <sys/errno.h>
 #include <sys/types.h>
 #include <kern/panic.h>
 #include <os/trace.h>
@@ -111,6 +112,46 @@ acpi_query(const char *s)
     return NULL;
 }
 
+int
+acpi_read_madt(uint32_t type, int(*cb)(struct apic_header *, size_t), size_t arg)
+{
+    static struct acpi_madt *madt;
+    struct apic_header *hdr;
+    uint8_t *cur, *end;
+    int retval;
+
+    if (cb == NULL) {
+        return -EINVAL;
+    }
+
+    if (madt == NULL) {
+        madt = acpi_query("APIC");
+    }
+
+    if (madt == NULL) {
+        panic("acpi: could not read MADT\n");
+    }
+
+    cur = (uint8_t *)(madt + 1);
+    end = (uint8_t *)madt + madt->hdr.length;
+
+    while (cur < end) {
+        hdr = (void *)cur;
+
+        if (hdr->type == type) {
+            retval = cb(hdr, arg);
+        }
+
+        if (retval >= 0) {
+            return retval;
+        }
+
+        cur += hdr->length;
+    }
+
+    return -1;
+}
+
 void
 acpi_init(void)
 {
-- 
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