Linux 3.8 compatibility hack

Since the following commit, the device would not turn off because the power
state is unknown. Until a fix is released in Linux (or until I know what
better to do), I just assume the power state D0.

commit ddc150f7a33ae0c9cb16eaac3641abc00f56316f
Author: Lv Zheng <lv.zheng@intel.com>
Date:   Fri Nov 16 02:46:28 2012 +0100

    ACPI / PM: Add check preventing transitioning to non-D0 state from D3.

    No power transitioning from D3 state up to a non-D0 state is allowed
    so make acpi_device_set_power() fail and complain if such a transition
    is attempted.

    Signed-off-by: Lv Zheng <lv.zheng@intel.com>
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

bbswitch.c

@@ -238,6 +238,20 @@ static void bbswitch_off(void) {
     pci_save_state(dis_dev);
     pci_clear_master(dis_dev);
     pci_disable_device(dis_dev);
+    do {
+        struct acpi_device *ad = NULL;
+        int r;
+
+        r = acpi_bus_get_device(dis_handle, &ad);
+        if (r || !ad) {
+            pr_warn("Cannot get ACPI device for PCI device\n");
+            break;
+        }
+        if (ad->power.state == ACPI_STATE_UNKNOWN) {
+            pr_debug("ACPI power state is unknown, forcing D0\n");
+            ad->power.state = ACPI_STATE_D0;
+        }
+    } while (0);
     pci_set_power_state(dis_dev, PCI_D3cold);
 
     if (bbswitch_acpi_off())