int count; /* Usage count */
wait_queue_head_t open_wait; /* Open waiters */
wait_queue_head_t close_wait; /* Close waiters */
+ wait_queue_head_t delta_msr_wait; /* Modem status change */
unsigned long flags; /* TTY flags ASY_*/
struct mutex mutex; /* Locking */
unsigned char *xmit_buf; /* Optional buffer */