Add support to read the _CLS entry if it's present. It is used by

memory-mapped devices that are normally PCIe drives. Devices can then use
the existing pci_get_class, etc. accessors to query this data.

The ivar values are different enough from the existing ACPI and ISA values
to not conflict.

Reviewed by:	jhb
Obtained from:	ABT Systems Ltd
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D8721

sys/dev/acpica/acpi.c

@@ -68,6 +68,8 @@ __FBSDID("$FreeBSD$");
 #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");
@@ -923,6 +925,15 @@ acpi_read_ivar(device_t dev, device_t child, int index, uintptr_t *result)
     case ISA_IVAR_LOGICALID:
 	*(int *)result = acpi_isa_get_logicalid(child);
 	break;
+    case PCI_IVAR_CLASS:
+	*(uint8_t*)result = (ad->ad_cls_class >> 16) & 0xff;
+	break;
+    case PCI_IVAR_SUBCLASS:
+	*(uint8_t*)result = (ad->ad_cls_class >> 8) & 0xff;
+	break;
+    case PCI_IVAR_PROGIF:
+	*(uint8_t*)result = (ad->ad_cls_class >> 0) & 0xff;
+	break;
     default:
 	return (ENOENT);
     }
@@ -1961,6 +1972,8 @@ acpi_probe_order(ACPI_HANDLE handle, int *order)
 static ACPI_STATUS
 acpi_probe_child(ACPI_HANDLE handle, UINT32 level, void *context, void **status)
 {
+    ACPI_DEVICE_INFO *devinfo;
+    struct acpi_device	*ad;
     struct acpi_prw_data prw;
     ACPI_OBJECT_TYPE type;
     ACPI_HANDLE h;
@@ -2054,6 +2067,17 @@ acpi_probe_child(ACPI_HANDLE handle, UINT32 level, void *context, void **status)
 	     * device not to have any resources.
 	     */
 	    acpi_parse_resources(child, handle, &acpi_res_parse_set, NULL);
+
+	    ad = device_get_ivars(child);
+	    ad->ad_cls_class = 0xffffff;
+	    if (ACPI_SUCCESS(AcpiGetObjectInfo(handle, &devinfo))) {
+		if ((devinfo->Valid & ACPI_VALID_CLS) != 0 &&
+		    devinfo->ClassCode.Length >= ACPI_PCICLS_STRING_SIZE) {
+		    ad->ad_cls_class = strtoul(devinfo->ClassCode.String,
+			NULL, 16);
+		}
+		AcpiOsFree(devinfo);
+	    }
 	    break;
 	}
     }

sys/dev/acpica/acpivar.h

@@ -85,6 +85,7 @@ struct acpi_device {
     ACPI_HANDLE			ad_handle;
     void			*ad_private;
     int				ad_flags;
+    int				ad_cls_class;
 
     /* Resources */
     struct resource_list	ad_rl;