[PATCH net v2] can: isotp: check register_netdevice_notifier() error in module init

[Minhong He]

Register the netdevice notifier before can_proto_register() and check the
return value. If protocol registration fails, unregister the notifier
before returning the error.

Align isotp_module_init() with the reordering already done for raw.c
(commit c28b3bffe49e ("can: raw: process optimization in raw_init()")) and
bcm.c (commit edd1a7e42f1d ("can: bcm: registration process optimization
in bcm_module_init()")).

Fixes: 8d0caedb7596 ("can: bcm/raw/isotp: use per module netdevice notifier")

Signed-off-by: Minhong He <heminhong@xxxxxxxxxx>
---
v2:
- Register the notifier before can_proto_register(), matching raw/bcm
- Reference the raw.c and bcm.c reordering commits as requested
v1: https://lore.kernel.org/all/20260728031038.76524-1-heminhong@xxxxxxxxxx/

 net/can/isotp.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/net/can/isotp.c b/net/can/isotp.c
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1907,13 +1907,18 @@
 
 	pr_info("can: isotp protocol (max_pdu_size %d)\n", max_pdu_size);
 
+	err = register_netdevice_notifier(&canisotp_notifier);
+	if (err)
+		return err;
+
 	err = can_proto_register(&isotp_can_proto);
-	if (err < 0)
+	if (err < 0) {
 		pr_err("can: registration of isotp protocol failed %pe\n", ERR_PTR(err));
-	else
-		register_netdevice_notifier(&canisotp_notifier);
+		unregister_netdevice_notifier(&canisotp_notifier);
+		return err;
+	}
 
-	return err;
+	return 0;
 }
 
 static __exit void isotp_module_exit(void)
-- 
2.25.1