1 files changed, 36 insertions, 0 deletions
diff --git a/sys/firmware/acpi/acpi_subr.c b/sys/firmware/acpi/acpi_subr.c
index d9ea694..7212602 100644
--- a/sys/firmware/acpi/acpi_subr.c
+++ b/sys/firmware/acpi/acpi_subr.c
@@ -31,6 +31,8 @@
 
 #include <firmware/acpi/acpi.h>
 #include <firmware/acpi/tables.h>
+#include <vm/vm.h>
+#include <string.h>
 
 bool
 acpi_is_checksum_valid(struct acpi_header *hdr)
@@ -45,3 +47,37 @@ acpi_is_checksum_valid(struct acpi_header *hdr)
     /* Sum of table (from header to end) must be zero!! */
     return sum == 0;
 }
+
+/*
+ * Looks up an ACPI table with a specific
+ * signature e.g "APIC" for MADT (if present).
+ *
+ * @query: The specific query to make e.g "APIC"
+ */
+void *
+acpi_query(const char *query)
+{
+    struct acpi_header *hdr;
+    struct acpi_root_sdt *root_sdt;
+    size_t root_sdt_len, signature_len;
+
+    root_sdt = acpi_get_root_sdt();
+    root_sdt_len = acpi_get_root_sdt_len();
+
+    /*
+     * XXX: Just a reminder, sizeof() is compile time.
+     *      There will be no actual reading,
+     *      so this is safe.
+     */
+    signature_len = sizeof(hdr->signature);
+
+    for (size_t i = 0; i < root_sdt_len; ++i) {
+        hdr = (struct acpi_header *)PHYS_TO_VIRT(root_sdt->tables[i]);
+
+        if (memcmp(hdr->signature, query, signature_len) == 0) {
+            return (void *)hdr;
+        }
+    }
+
+    return NULL;
+}