mei: bus: add reference to bus device in struct mei_cl_client

Add reference to the bus device (mei_device) for easier access.
To ensures that referencing cldev->bus is valid during cldev life time
we increase the bus ref counter on a client device creation and drop it
on the device release.
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/bus.c

@@ -590,6 +590,20 @@ static struct bus_type mei_cl_bus_type = {
 	.uevent		= mei_cl_device_uevent,
 };
 
+static struct mei_device *mei_dev_bus_get(struct mei_device *bus)
+{
+	if (bus)
+		get_device(bus->dev);
+
+	return bus;
+}
+
+static void mei_dev_bus_put(struct mei_device *bus)
+{
+	if (bus)
+		put_device(bus->dev);
+}
+
 static void mei_cl_dev_release(struct device *dev)
 {
 	struct mei_cl_device *cldev = to_mei_cl_device(dev);
@@ -598,6 +612,7 @@ static void mei_cl_dev_release(struct device *dev)
 		return;
 
 	mei_me_cl_put(cldev->me_cl);
+	mei_dev_bus_put(cldev->bus);
 	kfree(cldev);
 }
 
@@ -641,6 +656,7 @@ struct mei_cl_device *mei_cl_add_device(struct mei_device *bus,
 	cldev->dev.parent = bus->dev;
 	cldev->dev.bus = &mei_cl_bus_type;
 	cldev->dev.type = &mei_cl_device_type;
+	cldev->bus      = mei_dev_bus_get(bus);
 
 	strlcpy(cldev->name, name, sizeof(cldev->name));
 
@@ -650,6 +666,7 @@ struct mei_cl_device *mei_cl_add_device(struct mei_device *bus,
 	if (status) {
 		dev_err(bus->dev, "Failed to register MEI device\n");
 		mei_me_cl_put(cldev->me_cl);
+		mei_dev_bus_put(bus);
 		kfree(cldev);
 		return NULL;
 	}

include/linux/mei_cl_bus.h

@@ -6,6 +6,7 @@
 #include <linux/mod_devicetable.h>
 
 struct mei_cl_device;
+struct mei_device;
 
 typedef void (*mei_cl_event_cb_t)(struct mei_cl_device *device,
 			       u32 events, void *context);
@@ -17,6 +18,7 @@ typedef void (*mei_cl_event_cb_t)(struct mei_cl_device *device,
  * Drivers for MEI devices will get an mei_cl_device pointer
  * when being probed and shall use it for doing ME bus I/O.
  *
+ * @bus: parent mei device
  * @dev: linux driver model device pointer
  * @me_cl: me client
  * @cl: mei client
@@ -29,6 +31,7 @@ typedef void (*mei_cl_event_cb_t)(struct mei_cl_device *device,
  * @priv_data: client private data
  */
 struct mei_cl_device {
+	struct mei_device *bus;
 	struct device dev;
 
 	struct mei_me_client *me_cl;