[PATCH] tty: n_null: remove legacy BUG_ON() from module initialization

[Bramwel Barack]

The use of BUG_ON() in module initialization paths is heavily deprecated
as it triggers a kernel panic and crashes the entire system for non-fatal
registration failures. If tty_register_ldisc() fails (e.g., if the slot
is already occupied), it should be handled gracefully.

Modernize the initialization path by capturing the return value of
tty_register_ldisc(), logging a clean error message via pr_err(), and
propagating the error code back up to the module loader.

Signed-off-by: Bramwel Barack <bramwelbarack89@xxxxxxxxx>
---
 drivers/tty/n_null.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/n_null.c b/drivers/tty/n_null.c
index 5a429d923eb3..886f6789f872 100644
--- a/drivers/tty/n_null.c
+++ b/drivers/tty/n_null.c
@@ -32,7 +32,14 @@ static struct tty_ldisc_ops null_ldisc = {
 
 static int __init n_null_init(void)
 {
-	BUG_ON(tty_register_ldisc(&null_ldisc));
+	int ret;
+
+	ret = tty_register_ldisc(&null_ldisc);
+	if (ret) {
+		pr_err("n_null: failed to register line discipline (%d)\n", ret);
+		return ret;
+	}
+
 	return 0;
 }
 
-- 
2.56.0