extern void deactivate_chan(struct list_head *chans, int irq);
extern void reactivate_chan(struct list_head *chans, int irq);
extern void chan_enable_winch(struct list_head *chans, struct tty_struct *tty);
-extern void enable_chan(struct line *line);
+extern int enable_chan(struct line *line);
extern void close_chan(struct list_head *chans, int delay_free_irq);
extern int chan_window_size(struct list_head *chans,
unsigned short *rows_out,