greybus: control: Mode-switch is a 'core' operation

The operation layer allows only the 'core' operations on a connection,
which is in its 'disconnecting' state.

Mode switch is sent at the very end of interface-disable sequence, and
the control connection is already in its 'disconnecting' state at that
time. And so gb_operation_get_active() always fail with error -ENOTCONN.

The operation core already has support for such 'core' operations, just
that we were missing the needed flag while creating the mode switch
operation.

Fix that.

Tested on EVT 1.5 with gpbridge-test module.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Karthik Ravi Shankar <karthikrs@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/control.c

@@ -163,18 +163,24 @@ int gb_control_disconnecting_operation(struct gb_control *control,
 
 int gb_control_mode_switch_operation(struct gb_control *control)
 {
+	struct gb_operation *operation;
 	int ret;
 
-	ret = gb_operation_unidirectional(control->connection,
-						GB_CONTROL_TYPE_MODE_SWITCH,
-						NULL, 0);
+	operation = gb_operation_create_core(control->connection,
+					GB_CONTROL_TYPE_MODE_SWITCH,
+					0, 0, GB_OPERATION_FLAG_UNIDIRECTIONAL,
+					GFP_KERNEL);
+	if (!operation)
+		return -ENOMEM;
+
+	ret = gb_operation_request_send_sync(operation);
 	if (ret) {
-		dev_err(&control->dev, "failed to send mode switch: %d\n",
-				ret);
-		return ret;
+		dev_err(&control->dev, "failed to send mode switch: %d\n", ret);
 	}
 
-	return 0;
+	gb_operation_put(operation);
+
+	return ret;
 }
 
 int gb_control_timesync_enable(struct gb_control *control, u8 count,