EDAC/sysfs: move to use bus_get_dev_root()

Direct access to the struct bus_type dev_root pointer is going away soon
so replace that with a call to bus_get_dev_root() instead, which is what
it is there for.

Cc: Borislav Petkov <[e-mail]>
Cc: Tony Luck <[e-mail]>
Cc: James Morse <[e-mail]>
Cc: Mauro Carvalho Chehab <[e-mail]>
Cc: Robert Richter <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/edac/edac_device_sysfs.c

···
  */
 int edac_device_register_sysfs_main_kobj(struct edac_device_ctl_info *edac_dev)
 {
+	struct device *dev_root;
 	struct bus_type *edac_subsys;
-	int err;
+	int err = -ENODEV;
 
 	edac_dbg(1, "\n");
 
···
 	 */
 	edac_dev->owner = THIS_MODULE;
 
-	if (!try_module_get(edac_dev->owner)) {
-		err = -ENODEV;
+	if (!try_module_get(edac_dev->owner))
 		goto err_out;
-	}
 
 	/* register */
-	err = kobject_init_and_add(&edac_dev->kobj, &ktype_device_ctrl,
-				   &edac_subsys->dev_root->kobj,
-				   "%s", edac_dev->name);
+	dev_root = bus_get_dev_root(edac_subsys);
+	if (dev_root) {
+		err = kobject_init_and_add(&edac_dev->kobj, &ktype_device_ctrl,
+					   &dev_root->kobj, "%s", edac_dev->name);
+		put_device(dev_root);
+	}
 	if (err) {
 		edac_dbg(1, "Failed to register '.../edac/%s'\n",
 			 edac_dev->name);

drivers/edac/edac_pci_sysfs.c

···
  */
 static int edac_pci_main_kobj_setup(void)
 {
-	int err;
+	int err = -ENODEV;
 	struct bus_type *edac_subsys;
+	struct device *dev_root;
 
 	edac_dbg(0, "\n");
 
···
 	 */
 	if (!try_module_get(THIS_MODULE)) {
 		edac_dbg(1, "try_module_get() failed\n");
-		err = -ENODEV;
 		goto decrement_count_fail;
 	}
 
···
 	}
 
 	/* Instanstiate the pci object */
-	err = kobject_init_and_add(edac_pci_top_main_kobj,
-				   &ktype_edac_pci_main_kobj,
-				   &edac_subsys->dev_root->kobj, "pci");
+	dev_root = bus_get_dev_root(edac_subsys);
+	if (dev_root) {
+		err = kobject_init_and_add(edac_pci_top_main_kobj,
+					   &ktype_edac_pci_main_kobj,
+					   &dev_root->kobj, "pci");
+		put_device(dev_root);
+	}
 	if (err) {
 		edac_dbg(1, "Failed to register '.../edac/pci'\n");
 		goto kobject_init_and_add_fail;