sp1: acpi: Add ACPI table query function

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

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

@@ -15,6 +15,7 @@
 #include <os/knot.h>
 #include <os/bpt.h>
 #include <mm/vm.h>
+#include <string.h>
 
 #define pr_trace(fmt, ...) \
     printf("acpi: " fmt, ##__VA_ARGS__)
@@ -53,6 +54,27 @@ rsdp_verify(void)
     }
 }
 
+void *
+acpi_query(const char *signature)
+{
+    struct acpi_header *hdr;
+    uintptr_t pma;
+
+    if (signature == NULL) {
+        return NULL;
+    }
+
+    for (size_t i = 0; i < root_sdt_entries; ++i) {
+        pma = (uintptr_t)root_sdt->tables[i];
+        hdr = (struct acpi_header *)pma_to_vma(pma);
+        if (memcmp(hdr->signature, signature, sizeof(hdr->signature)) == 0) {
+            return (void *)hdr;
+        }
+    }
+
+    return NULL;
+}
+
 void
 acpi_init(void)
 {

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

@@ -17,4 +17,14 @@
  */
 void acpi_init(void);
 
+/*
+ * Query an ACPI table through its signature
+ *
+ * @signature: Signature to lookup
+ *
+ * Returns the virtual table base on success, otherwise
+ * NULL on failure.
+ */
+void *acpi_query(const char *signature);
+
 #endif  /* !_ACPI_ACPI_H_ */