+struct kgdb_nmi_tty_priv {
+	struct tty_port port;
+	int opened;
+	struct tasklet_struct tlet;
+	STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo;

I don't see where "opened" is used.

+static const struct tty_operations kgdb_nmi_tty_ops = {
+	.open		= kgdb_nmi_tty_open,
+	.close		= kgdb_nmi_tty_close,
+	.install	= kgdb_nmi_tty_install,
+	.cleanup	= kgdb_nmi_tty_cleanup,
+	.write_room	= kgdb_nmi_tty_write_room,
+	.write		= kgdb_nmi_tty_write,

And a hangup method (just using tty_port helpers will do the job - it's
needed so vhangup() works as expected on a port)


Alan