ACPI / scan: Indicate to platform when hot remove returns busy

In hotplug logic, it always indicates non-specific failure to
platform through _OST when handing ACPI hot-remove event failed. Then
platform terminates the hot-remove process but it can not identify
the reason.

Base on current hot-remove code, there have two situations that it
returns busy:

 - OSPM try to offline an individual device, but the device offline
   function returns "busy".

 - When the ejection event is applied to an "not offlined yet"
   container.  OSPM sends a kobject change event to userspace and
   returns "busy".

Both of them will returns -EBUSY to ACPI device hotplug function.
Then, the hotplug function indicates non-specific failure to platform
just like for any other error, e.g. -ENODEV or -EIO.

The benefit to the platform for identifying the OS "busy" state is
that it can use a different approach to handle the "busy" instead of
simply terminating the hot-remove operation for an unknown reason.
For example, the platform can wait for a while and then re-trigger
hot-remove.

Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
[ rjw: Changelog massage ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/scan.c

@@ -404,10 +404,6 @@ void acpi_device_hotplug(struct acpi_device *adev, u32 src)
 		error = dock_notify(adev, src);
 	} else if (adev->flags.hotplug_notify) {
 		error = acpi_generic_hotplug_event(adev, src);
-		if (error == -EPERM) {
-			ost_code = ACPI_OST_SC_EJECT_NOT_SUPPORTED;
-			goto err_out;
-		}
 	} else {
 		int (*notify)(struct acpi_device *, u32);
 
@@ -423,8 +419,20 @@ void acpi_device_hotplug(struct acpi_device *adev, u32 src)
 		else
 			goto out;
 	}
-	if (!error)
+	switch (error) {
+	case 0:
 		ost_code = ACPI_OST_SC_SUCCESS;
+		break;
+	case -EPERM:
+		ost_code = ACPI_OST_SC_EJECT_NOT_SUPPORTED;
+		break;
+	case -EBUSY:
+		ost_code = ACPI_OST_SC_DEVICE_BUSY;
+		break;
+	default:
+		ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE;
+		break;
+	}
 
  err_out:
 	acpi_evaluate_ost(adev->handle, src, ost_code, NULL);