Index: sys/dev/acpica/acpi.c
===================================================================
--- sys/dev/acpica/acpi.c
+++ sys/dev/acpica/acpi.c
@@ -68,6 +68,8 @@
 #include <dev/acpica/acpivar.h>
 #include <dev/acpica/acpiio.h>
 
+#include <dev/pci/pcivar.h>
+
 #include <vm/vm_param.h>
 
 static MALLOC_DEFINE(M_ACPIDEV, "acpidev", "ACPI devices");
@@ -897,13 +899,18 @@
 static int
 acpi_read_ivar(device_t dev, device_t child, int index, uintptr_t *result)
 {
+    ACPI_DEVICE_INFO	*devinfo;
     struct acpi_device	*ad;
+    u_long		class;
+    int			error;
 
     if ((ad = device_get_ivars(child)) == NULL) {
 	device_printf(child, "device has no ivars\n");
 	return (ENOENT);
     }
 
+    error = 0;
+
     /* ACPI and ISA compatibility ivars */
     switch(index) {
     case ACPI_IVAR_HANDLE:
@@ -923,11 +930,29 @@
     case ISA_IVAR_LOGICALID:
 	*(int *)result = acpi_isa_get_logicalid(child);
 	break;
+    case PCI_IVAR_CLASS:
+    case PCI_IVAR_SUBCLASS:
+    case PCI_IVAR_PROGIF:
+	if (ACPI_FAILURE(AcpiGetObjectInfo(ad->ad_handle, &devinfo)))
+	    return (ENOENT);
+	if ((devinfo->Valid & ACPI_VALID_CLS) != 0 &&
+	    devinfo->ClassCode.Length >= ACPI_PCICLS_STRING_SIZE) {
+	    class = strtoul(devinfo->ClassCode.String, NULL, 16);
+	    if (index == PCI_IVAR_CLASS)
+		*(uint8_t*)result = (class >> 16) & 0xff;
+	    else if (index == PCI_IVAR_SUBCLASS)
+		*(uint8_t*)result = (class >> 8) & 0xff;
+	    else
+		*(uint8_t*)result = (class >> 0) & 0xff;
+	} else
+	    error = ENOENT;
+	AcpiOsFree(devinfo);
+	break;
     default:
 	return (ENOENT);
     }
 
-    return (0);
+    return (error);
 }
 
 static int