mei: bus: prevent hardware module unload if device on bus is active

The hardware module should not be unloaded if the bus
has active devices.
Get get_/put_ bus parent module upon client device
connection/disconnection, to prevent the hardware managing
module to disappear underneath.
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/bus.c

@@ -541,6 +541,37 @@ int mei_cldev_disable(struct mei_cl_device *cldev)
 }
 EXPORT_SYMBOL_GPL(mei_cldev_disable);
 
+/**
+ * mei_cl_bus_module_get - acquire module of the underlying
+ *    hw module.
+ *
+ * @cl: host client
+ *
+ * Return: true on success; false if the module was removed.
+ */
+bool mei_cl_bus_module_get(struct mei_cl *cl)
+{
+	struct mei_cl_device *cldev = cl->cldev;
+
+	if (!cldev)
+		return true;
+
+	return try_module_get(cldev->bus->dev->driver->owner);
+}
+
+/**
+ * mei_cl_bus_module_put -  release the underlying hw module.
+ *
+ * @cl: host client
+ */
+void mei_cl_bus_module_put(struct mei_cl *cl)
+{
+	struct mei_cl_device *cldev = cl->cldev;
+
+	if (cldev)
+		module_put(cldev->bus->dev->driver->owner);
+}
+
 /**
  * mei_cl_device_find - find matching entry in the driver id table
  *

drivers/misc/mei/client.c

@@ -774,6 +774,8 @@ static void mei_cl_set_disconnected(struct mei_cl *cl)
 	cl->tx_flow_ctrl_creds = 0;
 	cl->timer_count = 0;
 
+	mei_cl_bus_module_put(cl);
+
 	if (!cl->me_cl)
 		return;
 
@@ -1077,13 +1079,17 @@ int mei_cl_connect(struct mei_cl *cl, struct mei_me_client *me_cl,
 
 	dev = cl->dev;
 
+	if (!mei_cl_bus_module_get(cl))
+		return -ENODEV;
+
 	rets = mei_cl_set_connecting(cl, me_cl);
 	if (rets)
-		return rets;
+		goto nortpm;
 
 	if (mei_cl_is_fixed_address(cl)) {
 		cl->state = MEI_FILE_CONNECTED;
-		return 0;
+		rets = 0;
+		goto nortpm;
 	}
 
 	rets = pm_runtime_get(dev->dev);

drivers/misc/mei/mei_dev.h

@@ -328,6 +328,8 @@ ssize_t __mei_cl_recv(struct mei_cl *cl, u8 *buf, size_t length,
 bool mei_cl_bus_rx_event(struct mei_cl *cl);
 bool mei_cl_bus_notify_event(struct mei_cl *cl);
 void mei_cl_bus_remove_devices(struct mei_device *bus);
+bool mei_cl_bus_module_get(struct mei_cl *cl);
+void mei_cl_bus_module_put(struct mei_cl *cl);
 int mei_cl_bus_init(void);
 void mei_cl_bus_exit(void);