15  * This module implements the tty line discipline N_HDLC for use with
16  * tty device drivers that support bit-synchronous HDLC communications.
20  * 1. tty write calls represent one complete transmit frame of data
33  *    the tty flip buffer and call the line discipline receive
39  *    tty read calls.
41  * 3. tty read calls returns an entire frame of data or nothing.
45  *    of the tty flags
52  * These conventions allow the standard tty programming interface
92 #include <linux/tty.h>
94 #include <linux/string.h>	/* used in new tty drivers */
95 #include <linux/signal.h>	/* used in new tty drivers */
100 #include "tty.h"
131  * @tty_for_write_work: pointer to tty instance used by the @write_work
161 static void flush_rx_queue(struct tty_struct *tty)  in flush_rx_queue()  argument
163 	struct n_hdlc *n_hdlc = tty->disc_data;  in flush_rx_queue()
170 static void flush_tx_queue(struct tty_struct *tty)  in flush_tx_queue()  argument
172 	struct n_hdlc *n_hdlc = tty->disc_data;  in flush_tx_queue()
191  * @tty: pointer to tty info structure
194  * else, the tty is closed, or the tty detects a hangup.
196 static void n_hdlc_tty_close(struct tty_struct *tty)  in n_hdlc_tty_close()  argument
198 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_close()
201 	clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags);  in n_hdlc_tty_close()
203 	tty->disc_data = NULL;  in n_hdlc_tty_close()
206 	wake_up_interruptible(&tty->read_wait);  in n_hdlc_tty_close()
207 	wake_up_interruptible(&tty->write_wait);  in n_hdlc_tty_close()
220  * @tty: pointer to tty info structure
224 static int n_hdlc_tty_open(struct tty_struct *tty)  in n_hdlc_tty_open()  argument
226 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_open()
228 	pr_debug("%s() called (device=%s)\n", __func__, tty->name);  in n_hdlc_tty_open()
232 		pr_err("%s: tty already associated!\n", __func__);  in n_hdlc_tty_open()
243 	n_hdlc->tty_for_write_work = tty;  in n_hdlc_tty_open()
244 	tty->disc_data = n_hdlc;  in n_hdlc_tty_open()
245 	tty->receive_room = 65536;  in n_hdlc_tty_open()
248 	set_bit(TTY_NO_WRITE_SPLIT, &tty->flags);  in n_hdlc_tty_open()
251 	tty_driver_flush_buffer(tty);  in n_hdlc_tty_open()
260  * @tty: pointer to tty instance data
264  * list and by the tty wakeup callback.
266 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)  in n_hdlc_send_frames()  argument
286 		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);  in n_hdlc_send_frames()
287 		actual = tty->ops->write(tty, tbuf->buf, tbuf->count);  in n_hdlc_send_frames()
306 			wake_up_interruptible(&tty->write_wait);  in n_hdlc_send_frames()
323 		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);  in n_hdlc_send_frames()
342 	struct tty_struct *tty = n_hdlc->tty_for_write_work;  in n_hdlc_tty_write_work()  local
344 	n_hdlc_send_frames(n_hdlc, tty);  in n_hdlc_tty_write_work()
349  * @tty: pointer to associated tty instance data
353 static void n_hdlc_tty_wakeup(struct tty_struct *tty)  in n_hdlc_tty_wakeup()  argument
355 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_wakeup()
361  * n_hdlc_tty_receive - Called by tty driver when receive data is available
362  * @tty: pointer to tty instance data
367  * Called by tty low level driver when receive data is available. Data is
370 static void n_hdlc_tty_receive(struct tty_struct *tty, const u8 *data,  in n_hdlc_tty_receive()  argument
373 	register struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_receive()
407 	wake_up_interruptible(&tty->read_wait);  in n_hdlc_tty_receive()
408 	if (tty->fasync != NULL)  in n_hdlc_tty_receive()
409 		kill_fasync(&tty->fasync, SIGIO, POLL_IN);  in n_hdlc_tty_receive()
415  * @tty: pointer to tty instance data
424 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,  in n_hdlc_tty_read()  argument
428 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_read()
438 	add_wait_queue(&tty->read_wait, &wait);  in n_hdlc_tty_read()
441 		if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {  in n_hdlc_tty_read()
455 		if (tty_io_nonblock(tty, file)) {  in n_hdlc_tty_read()
468 	remove_wait_queue(&tty->read_wait, &wait);  in n_hdlc_tty_read()
510  * @tty: pointer to associated tty device instance data
517 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,  in n_hdlc_tty_write()  argument
520 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_write()
534 	add_wait_queue(&tty->write_wait, &wait);  in n_hdlc_tty_write()
543 		if (tty_io_nonblock(tty, file)) {  in n_hdlc_tty_write()
556 	remove_wait_queue(&tty->write_wait, &wait);  in n_hdlc_tty_write()
565 		n_hdlc_send_frames(n_hdlc, tty);  in n_hdlc_tty_write()
573  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
574  * @tty: pointer to tty instance data
580 static int n_hdlc_tty_ioctl(struct tty_struct *tty, unsigned int cmd,  in n_hdlc_tty_ioctl()  argument
583 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_ioctl()
605 		count = tty_chars_in_buffer(tty);  in n_hdlc_tty_ioctl()
619 			flush_tx_queue(tty);  in n_hdlc_tty_ioctl()
624 		return n_tty_ioctl_helper(tty, cmd, arg);  in n_hdlc_tty_ioctl()
629  * n_hdlc_tty_poll - TTY callback for poll system call
630  * @tty: pointer to tty instance data
638 static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,  in n_hdlc_tty_poll()  argument
641 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_poll()
648 	poll_wait(filp, &tty->read_wait, wait);  in n_hdlc_tty_poll()
649 	poll_wait(filp, &tty->write_wait, wait);  in n_hdlc_tty_poll()
654 	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))  in n_hdlc_tty_poll()
658 	if (!tty_is_writelocked(tty) &&  in n_hdlc_tty_poll()