mei: bus: use zero vtag for bus clients.

The zero vtag is required for the read flow to work also for
devices on the mei client bus.
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Link: https://lore.kernel.org/r/20200818115147.2567012-10-tomas.winkler@intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/bus.c

@@ -495,6 +495,68 @@ static void mei_cl_bus_module_put(struct mei_cl_device *cldev)
 	module_put(cldev->bus->dev->driver->owner);
 }
 
+/**
+ * mei_cl_bus_vtag - get bus vtag entry wrapper
+ *     The tag for bus client is always first.
+ *
+ * @cl: host client
+ *
+ * Return: bus vtag or NULL
+ */
+static inline struct mei_cl_vtag *mei_cl_bus_vtag(struct mei_cl *cl)
+{
+	return list_first_entry_or_null(&cl->vtag_map,
+					struct mei_cl_vtag, list);
+}
+
+/**
+ * mei_cl_bus_vtag_alloc - add bus client entry to vtag map
+ *
+ * @cldev: me client device
+ *
+ * Return:
+ * * 0 on success
+ * * -ENOMEM if memory allocation failed
+ */
+static int mei_cl_bus_vtag_alloc(struct mei_cl_device *cldev)
+{
+	struct mei_cl *cl = cldev->cl;
+	struct mei_cl_vtag *cl_vtag;
+
+	/*
+	 * Bail out if the client does not supports vtags
+	 * or has already allocated one
+	 */
+	if (mei_cl_vt_support_check(cl) || mei_cl_bus_vtag(cl))
+		return 0;
+
+	cl_vtag = mei_cl_vtag_alloc(NULL, 0);
+	if (IS_ERR(cl_vtag))
+		return -ENOMEM;
+
+	list_add_tail(&cl_vtag->list, &cl->vtag_map);
+
+	return 0;
+}
+
+/**
+ * mei_cl_bus_vtag_free - remove the bus entry from vtag map
+ *
+ * @cldev: me client device
+ */
+static void mei_cl_bus_vtag_free(struct mei_cl_device *cldev)
+{
+	struct mei_cl *cl = cldev->cl;
+	struct mei_cl_vtag *cl_vtag;
+
+	cl_vtag = mei_cl_bus_vtag(cl);
+	if (!cl_vtag)
+		return;
+
+	list_del(&cl_vtag->list);
+	kfree(cl_vtag);
+}
+
 /**
  * mei_cldev_enable - enable me client device
  *     create connection with me client
@@ -531,9 +593,15 @@ int mei_cldev_enable(struct mei_cl_device *cldev)
 		goto out;
 	}
 
+	ret = mei_cl_bus_vtag_alloc(cldev);
+	if (ret)
+		goto out;
+
 	ret = mei_cl_connect(cl, cldev->me_cl, NULL);
-	if (ret < 0)
+	if (ret < 0) {
 		dev_err(&cldev->dev, "cannot connect\n");
+		mei_cl_bus_vtag_free(cldev);
+	}
 
 out:
 	mutex_unlock(&bus->device_lock);
@@ -586,6 +654,8 @@ int mei_cldev_disable(struct mei_cl_device *cldev)
 
 	mutex_lock(&bus->device_lock);
 
+	mei_cl_bus_vtag_free(cldev);
+
 	if (!mei_cl_is_connected(cl)) {
 		dev_dbg(bus->dev, "Already disconnected\n");
 		err = 0;