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1// SPDX-License-Identifier: GPL-1.0+
2/* generic HDLC line discipline for Linux
3 *
4 * Written by Paul Fulghum paulkf@microgate.com
5 * for Microgate Corporation
6 *
7 * Microgate and SyncLink are registered trademarks of Microgate Corporation
8 *
9 * Adapted from ppp.c, written by Michael Callahan <callahan@maths.ox.ac.uk>,
10 * Al Longyear <longyear@netcom.com>,
11 * Paul Mackerras <Paul.Mackerras@cs.anu.edu.au>
12 *
13 * Original release 01/11/99
14 *
15 * This module implements the tty line discipline N_HDLC for use with
16 * tty device drivers that support bit-synchronous HDLC communications.
17 *
18 * All HDLC data is frame oriented which means:
19 *
20 * 1. tty write calls represent one complete transmit frame of data
21 * The device driver should accept the complete frame or none of
22 * the frame (busy) in the write method. Each write call should have
23 * a byte count in the range of 2-65535 bytes (2 is min HDLC frame
24 * with 1 addr byte and 1 ctrl byte). The max byte count of 65535
25 * should include any crc bytes required. For example, when using
26 * CCITT CRC32, 4 crc bytes are required, so the maximum size frame
27 * the application may transmit is limited to 65531 bytes. For CCITT
28 * CRC16, the maximum application frame size would be 65533.
29 *
30 *
31 * 2. receive callbacks from the device driver represents
32 * one received frame. The device driver should bypass
33 * the tty flip buffer and call the line discipline receive
34 * callback directly to avoid fragmenting or concatenating
35 * multiple frames into a single receive callback.
36 *
37 * The HDLC line discipline queues the receive frames in separate
38 * buffers so complete receive frames can be returned by the
39 * tty read calls.
40 *
41 * 3. tty read calls returns an entire frame of data or nothing.
42 *
43 * 4. all send and receive data is considered raw. No processing
44 * or translation is performed by the line discipline, regardless
45 * of the tty flags
46 *
47 * 5. When line discipline is queried for the amount of receive
48 * data available (FIOC), 0 is returned if no data available,
49 * otherwise the count of the next available frame is returned.
50 * (instead of the sum of all received frame counts).
51 *
52 * These conventions allow the standard tty programming interface
53 * to be used for synchronous HDLC applications when used with
54 * this line discipline (or another line discipline that is frame
55 * oriented such as N_PPP).
56 *
57 * The SyncLink driver (synclink.c) implements both asynchronous
58 * (using standard line discipline N_TTY) and synchronous HDLC
59 * (using N_HDLC) communications, with the latter using the above
60 * conventions.
61 *
62 * This implementation is very basic and does not maintain
63 * any statistics. The main point is to enforce the raw data
64 * and frame orientation of HDLC communications.
65 *
66 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
67 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
68 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
69 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
70 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
71 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
72 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
73 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
74 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
75 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
76 * OF THE POSSIBILITY OF SUCH DAMAGE.
77 */
78
79#define HDLC_MAGIC 0x239e
80
81#include <linux/module.h>
82#include <linux/init.h>
83#include <linux/kernel.h>
84#include <linux/sched.h>
85#include <linux/types.h>
86#include <linux/fcntl.h>
87#include <linux/interrupt.h>
88#include <linux/ptrace.h>
89
90#include <linux/poll.h>
91#include <linux/in.h>
92#include <linux/ioctl.h>
93#include <linux/slab.h>
94#include <linux/tty.h>
95#include <linux/errno.h>
96#include <linux/string.h> /* used in new tty drivers */
97#include <linux/signal.h> /* used in new tty drivers */
98#include <linux/if.h>
99#include <linux/bitops.h>
100
101#include <asm/termios.h>
102#include <linux/uaccess.h>
103
104/*
105 * Buffers for individual HDLC frames
106 */
107#define MAX_HDLC_FRAME_SIZE 65535
108#define DEFAULT_RX_BUF_COUNT 10
109#define MAX_RX_BUF_COUNT 60
110#define DEFAULT_TX_BUF_COUNT 3
111
112struct n_hdlc_buf {
113 struct list_head list_item;
114 int count;
115 char buf[];
116};
117
118struct n_hdlc_buf_list {
119 struct list_head list;
120 int count;
121 spinlock_t spinlock;
122};
123
124/**
125 * struct n_hdlc - per device instance data structure
126 * @magic - magic value for structure
127 * @tbusy - reentrancy flag for tx wakeup code
128 * @woke_up - tx wakeup needs to be run again as it was called while @tbusy
129 * @tx_buf_list - list of pending transmit frame buffers
130 * @rx_buf_list - list of received frame buffers
131 * @tx_free_buf_list - list unused transmit frame buffers
132 * @rx_free_buf_list - list unused received frame buffers
133 */
134struct n_hdlc {
135 int magic;
136 bool tbusy;
137 bool woke_up;
138 struct n_hdlc_buf_list tx_buf_list;
139 struct n_hdlc_buf_list rx_buf_list;
140 struct n_hdlc_buf_list tx_free_buf_list;
141 struct n_hdlc_buf_list rx_free_buf_list;
142};
143
144/*
145 * HDLC buffer list manipulation functions
146 */
147static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
148 struct n_hdlc_buf *buf);
149static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
150 struct n_hdlc_buf *buf);
151static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
152
153/* Local functions */
154
155static struct n_hdlc *n_hdlc_alloc(void);
156
157/* max frame size for memory allocations */
158static int maxframe = 4096;
159
160static void flush_rx_queue(struct tty_struct *tty)
161{
162 struct n_hdlc *n_hdlc = tty->disc_data;
163 struct n_hdlc_buf *buf;
164
165 while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
166 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
167}
168
169static void flush_tx_queue(struct tty_struct *tty)
170{
171 struct n_hdlc *n_hdlc = tty->disc_data;
172 struct n_hdlc_buf *buf;
173
174 while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
175 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
176}
177
178static void n_hdlc_free_buf_list(struct n_hdlc_buf_list *list)
179{
180 struct n_hdlc_buf *buf;
181
182 do {
183 buf = n_hdlc_buf_get(list);
184 kfree(buf);
185 } while (buf);
186}
187
188/**
189 * n_hdlc_tty_close - line discipline close
190 * @tty - pointer to tty info structure
191 *
192 * Called when the line discipline is changed to something
193 * else, the tty is closed, or the tty detects a hangup.
194 */
195static void n_hdlc_tty_close(struct tty_struct *tty)
196{
197 struct n_hdlc *n_hdlc = tty->disc_data;
198
199 if (n_hdlc->magic != HDLC_MAGIC) {
200 pr_warn("n_hdlc: trying to close unopened tty!\n");
201 return;
202 }
203#if defined(TTY_NO_WRITE_SPLIT)
204 clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags);
205#endif
206 tty->disc_data = NULL;
207
208 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
209 wake_up_interruptible(&tty->read_wait);
210 wake_up_interruptible(&tty->write_wait);
211
212 n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list);
213 n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list);
214 n_hdlc_free_buf_list(&n_hdlc->rx_buf_list);
215 n_hdlc_free_buf_list(&n_hdlc->tx_buf_list);
216 kfree(n_hdlc);
217} /* end of n_hdlc_tty_close() */
218
219/**
220 * n_hdlc_tty_open - called when line discipline changed to n_hdlc
221 * @tty - pointer to tty info structure
222 *
223 * Returns 0 if success, otherwise error code
224 */
225static int n_hdlc_tty_open(struct tty_struct *tty)
226{
227 struct n_hdlc *n_hdlc = tty->disc_data;
228
229 pr_debug("%s() called (device=%s)\n", __func__, tty->name);
230
231 /* There should not be an existing table for this slot. */
232 if (n_hdlc) {
233 pr_err("%s: tty already associated!\n", __func__);
234 return -EEXIST;
235 }
236
237 n_hdlc = n_hdlc_alloc();
238 if (!n_hdlc) {
239 pr_err("%s: n_hdlc_alloc failed\n", __func__);
240 return -ENFILE;
241 }
242
243 tty->disc_data = n_hdlc;
244 tty->receive_room = 65536;
245
246 /* change tty_io write() to not split large writes into 8K chunks */
247 set_bit(TTY_NO_WRITE_SPLIT, &tty->flags);
248
249 /* flush receive data from driver */
250 tty_driver_flush_buffer(tty);
251
252 return 0;
253
254} /* end of n_tty_hdlc_open() */
255
256/**
257 * n_hdlc_send_frames - send frames on pending send buffer list
258 * @n_hdlc - pointer to ldisc instance data
259 * @tty - pointer to tty instance data
260 *
261 * Send frames on pending send buffer list until the driver does not accept a
262 * frame (busy) this function is called after adding a frame to the send buffer
263 * list and by the tty wakeup callback.
264 */
265static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
266{
267 register int actual;
268 unsigned long flags;
269 struct n_hdlc_buf *tbuf;
270
271check_again:
272
273 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
274 if (n_hdlc->tbusy) {
275 n_hdlc->woke_up = true;
276 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
277 return;
278 }
279 n_hdlc->tbusy = true;
280 n_hdlc->woke_up = false;
281 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
282
283 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
284 while (tbuf) {
285 pr_debug("sending frame %p, count=%d\n", tbuf, tbuf->count);
286
287 /* Send the next block of data to device */
288 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
289 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
290
291 /* rollback was possible and has been done */
292 if (actual == -ERESTARTSYS) {
293 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
294 break;
295 }
296 /* if transmit error, throw frame away by */
297 /* pretending it was accepted by driver */
298 if (actual < 0)
299 actual = tbuf->count;
300
301 if (actual == tbuf->count) {
302 pr_debug("frame %p completed\n", tbuf);
303
304 /* free current transmit buffer */
305 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
306
307 /* wait up sleeping writers */
308 wake_up_interruptible(&tty->write_wait);
309
310 /* get next pending transmit buffer */
311 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
312 } else {
313 pr_debug("frame %p pending\n", tbuf);
314
315 /*
316 * the buffer was not accepted by driver,
317 * return it back into tx queue
318 */
319 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
320 break;
321 }
322 }
323
324 if (!tbuf)
325 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
326
327 /* Clear the re-entry flag */
328 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
329 n_hdlc->tbusy = false;
330 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
331
332 if (n_hdlc->woke_up)
333 goto check_again;
334} /* end of n_hdlc_send_frames() */
335
336/**
337 * n_hdlc_tty_wakeup - Callback for transmit wakeup
338 * @tty - pointer to associated tty instance data
339 *
340 * Called when low level device driver can accept more send data.
341 */
342static void n_hdlc_tty_wakeup(struct tty_struct *tty)
343{
344 struct n_hdlc *n_hdlc = tty->disc_data;
345
346 n_hdlc_send_frames(n_hdlc, tty);
347} /* end of n_hdlc_tty_wakeup() */
348
349/**
350 * n_hdlc_tty_receive - Called by tty driver when receive data is available
351 * @tty - pointer to tty instance data
352 * @data - pointer to received data
353 * @flags - pointer to flags for data
354 * @count - count of received data in bytes
355 *
356 * Called by tty low level driver when receive data is available. Data is
357 * interpreted as one HDLC frame.
358 */
359static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
360 char *flags, int count)
361{
362 register struct n_hdlc *n_hdlc = tty->disc_data;
363 register struct n_hdlc_buf *buf;
364
365 pr_debug("%s() called count=%d\n", __func__, count);
366
367 /* verify line is using HDLC discipline */
368 if (n_hdlc->magic != HDLC_MAGIC) {
369 pr_err("line not using HDLC discipline\n");
370 return;
371 }
372
373 if (count > maxframe) {
374 pr_debug("rx count>maxframesize, data discarded\n");
375 return;
376 }
377
378 /* get a free HDLC buffer */
379 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
380 if (!buf) {
381 /*
382 * no buffers in free list, attempt to allocate another rx
383 * buffer unless the maximum count has been reached
384 */
385 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
386 buf = kmalloc(struct_size(buf, buf, maxframe),
387 GFP_ATOMIC);
388 }
389
390 if (!buf) {
391 pr_debug("no more rx buffers, data discarded\n");
392 return;
393 }
394
395 /* copy received data to HDLC buffer */
396 memcpy(buf->buf, data, count);
397 buf->count = count;
398
399 /* add HDLC buffer to list of received frames */
400 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
401
402 /* wake up any blocked reads and perform async signalling */
403 wake_up_interruptible(&tty->read_wait);
404 if (tty->fasync != NULL)
405 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
406
407} /* end of n_hdlc_tty_receive() */
408
409/**
410 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
411 * @tty - pointer to tty instance data
412 * @file - pointer to open file object
413 * @buf - pointer to returned data buffer
414 * @nr - size of returned data buffer
415 *
416 * Returns the number of bytes returned or error code.
417 */
418static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
419 __u8 __user *buf, size_t nr)
420{
421 struct n_hdlc *n_hdlc = tty->disc_data;
422 int ret = 0;
423 struct n_hdlc_buf *rbuf;
424 DECLARE_WAITQUEUE(wait, current);
425
426 add_wait_queue(&tty->read_wait, &wait);
427
428 for (;;) {
429 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
430 ret = -EIO;
431 break;
432 }
433 if (tty_hung_up_p(file))
434 break;
435
436 set_current_state(TASK_INTERRUPTIBLE);
437
438 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
439 if (rbuf) {
440 if (rbuf->count > nr) {
441 /* too large for caller's buffer */
442 ret = -EOVERFLOW;
443 } else {
444 __set_current_state(TASK_RUNNING);
445 if (copy_to_user(buf, rbuf->buf, rbuf->count))
446 ret = -EFAULT;
447 else
448 ret = rbuf->count;
449 }
450
451 if (n_hdlc->rx_free_buf_list.count >
452 DEFAULT_RX_BUF_COUNT)
453 kfree(rbuf);
454 else
455 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
456 break;
457 }
458
459 /* no data */
460 if (tty_io_nonblock(tty, file)) {
461 ret = -EAGAIN;
462 break;
463 }
464
465 schedule();
466
467 if (signal_pending(current)) {
468 ret = -EINTR;
469 break;
470 }
471 }
472
473 remove_wait_queue(&tty->read_wait, &wait);
474 __set_current_state(TASK_RUNNING);
475
476 return ret;
477
478} /* end of n_hdlc_tty_read() */
479
480/**
481 * n_hdlc_tty_write - write a single frame of data to device
482 * @tty - pointer to associated tty device instance data
483 * @file - pointer to file object data
484 * @data - pointer to transmit data (one frame)
485 * @count - size of transmit frame in bytes
486 *
487 * Returns the number of bytes written (or error code).
488 */
489static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
490 const unsigned char *data, size_t count)
491{
492 struct n_hdlc *n_hdlc = tty->disc_data;
493 int error = 0;
494 DECLARE_WAITQUEUE(wait, current);
495 struct n_hdlc_buf *tbuf;
496
497 pr_debug("%s() called count=%zd\n", __func__, count);
498
499 if (n_hdlc->magic != HDLC_MAGIC)
500 return -EIO;
501
502 /* verify frame size */
503 if (count > maxframe) {
504 pr_debug("%s: truncating user packet from %zu to %d\n",
505 __func__, count, maxframe);
506 count = maxframe;
507 }
508
509 add_wait_queue(&tty->write_wait, &wait);
510
511 for (;;) {
512 set_current_state(TASK_INTERRUPTIBLE);
513
514 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
515 if (tbuf)
516 break;
517
518 if (tty_io_nonblock(tty, file)) {
519 error = -EAGAIN;
520 break;
521 }
522 schedule();
523
524 if (signal_pending(current)) {
525 error = -EINTR;
526 break;
527 }
528 }
529
530 __set_current_state(TASK_RUNNING);
531 remove_wait_queue(&tty->write_wait, &wait);
532
533 if (!error) {
534 /* Retrieve the user's buffer */
535 memcpy(tbuf->buf, data, count);
536
537 /* Send the data */
538 tbuf->count = error = count;
539 n_hdlc_buf_put(&n_hdlc->tx_buf_list, tbuf);
540 n_hdlc_send_frames(n_hdlc, tty);
541 }
542
543 return error;
544
545} /* end of n_hdlc_tty_write() */
546
547/**
548 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
549 * @tty - pointer to tty instance data
550 * @file - pointer to open file object for device
551 * @cmd - IOCTL command code
552 * @arg - argument for IOCTL call (cmd dependent)
553 *
554 * Returns command dependent result.
555 */
556static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
557 unsigned int cmd, unsigned long arg)
558{
559 struct n_hdlc *n_hdlc = tty->disc_data;
560 int error = 0;
561 int count;
562 unsigned long flags;
563 struct n_hdlc_buf *buf = NULL;
564
565 pr_debug("%s() called %d\n", __func__, cmd);
566
567 /* Verify the status of the device */
568 if (n_hdlc->magic != HDLC_MAGIC)
569 return -EBADF;
570
571 switch (cmd) {
572 case FIONREAD:
573 /* report count of read data available */
574 /* in next available frame (if any) */
575 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags);
576 buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
577 struct n_hdlc_buf, list_item);
578 if (buf)
579 count = buf->count;
580 else
581 count = 0;
582 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags);
583 error = put_user(count, (int __user *)arg);
584 break;
585
586 case TIOCOUTQ:
587 /* get the pending tx byte count in the driver */
588 count = tty_chars_in_buffer(tty);
589 /* add size of next output frame in queue */
590 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
591 buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
592 struct n_hdlc_buf, list_item);
593 if (buf)
594 count += buf->count;
595 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
596 error = put_user(count, (int __user *)arg);
597 break;
598
599 case TCFLSH:
600 switch (arg) {
601 case TCIOFLUSH:
602 case TCOFLUSH:
603 flush_tx_queue(tty);
604 }
605 fallthrough; /* to default */
606
607 default:
608 error = n_tty_ioctl_helper(tty, file, cmd, arg);
609 break;
610 }
611 return error;
612
613} /* end of n_hdlc_tty_ioctl() */
614
615/**
616 * n_hdlc_tty_poll - TTY callback for poll system call
617 * @tty - pointer to tty instance data
618 * @filp - pointer to open file object for device
619 * @poll_table - wait queue for operations
620 *
621 * Determine which operations (read/write) will not block and return info
622 * to caller.
623 * Returns a bit mask containing info on which ops will not block.
624 */
625static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
626 poll_table *wait)
627{
628 struct n_hdlc *n_hdlc = tty->disc_data;
629 __poll_t mask = 0;
630
631 if (n_hdlc->magic != HDLC_MAGIC)
632 return 0;
633
634 /*
635 * queue the current process into any wait queue that may awaken in the
636 * future (read and write)
637 */
638 poll_wait(filp, &tty->read_wait, wait);
639 poll_wait(filp, &tty->write_wait, wait);
640
641 /* set bits for operations that won't block */
642 if (!list_empty(&n_hdlc->rx_buf_list.list))
643 mask |= EPOLLIN | EPOLLRDNORM; /* readable */
644 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
645 mask |= EPOLLHUP;
646 if (tty_hung_up_p(filp))
647 mask |= EPOLLHUP;
648 if (!tty_is_writelocked(tty) &&
649 !list_empty(&n_hdlc->tx_free_buf_list.list))
650 mask |= EPOLLOUT | EPOLLWRNORM; /* writable */
651
652 return mask;
653} /* end of n_hdlc_tty_poll() */
654
655static void n_hdlc_alloc_buf(struct n_hdlc_buf_list *list, unsigned int count,
656 const char *name)
657{
658 struct n_hdlc_buf *buf;
659 unsigned int i;
660
661 for (i = 0; i < count; i++) {
662 buf = kmalloc(struct_size(buf, buf, maxframe), GFP_KERNEL);
663 if (!buf) {
664 pr_debug("%s(), kmalloc() failed for %s buffer %u\n",
665 __func__, name, i);
666 return;
667 }
668 n_hdlc_buf_put(list, buf);
669 }
670}
671
672/**
673 * n_hdlc_alloc - allocate an n_hdlc instance data structure
674 *
675 * Returns a pointer to newly created structure if success, otherwise %NULL
676 */
677static struct n_hdlc *n_hdlc_alloc(void)
678{
679 struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL);
680
681 if (!n_hdlc)
682 return NULL;
683
684 spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);
685 spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
686 spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
687 spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
688
689 INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);
690 INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);
691 INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);
692 INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);
693
694 n_hdlc_alloc_buf(&n_hdlc->rx_free_buf_list, DEFAULT_RX_BUF_COUNT, "rx");
695 n_hdlc_alloc_buf(&n_hdlc->tx_free_buf_list, DEFAULT_TX_BUF_COUNT, "tx");
696
697 /* Initialize the control block */
698 n_hdlc->magic = HDLC_MAGIC;
699
700 return n_hdlc;
701
702} /* end of n_hdlc_alloc() */
703
704/**
705 * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
706 * @buf_list - pointer to the buffer list
707 * @buf - pointer to the buffer
708 */
709static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
710 struct n_hdlc_buf *buf)
711{
712 unsigned long flags;
713
714 spin_lock_irqsave(&buf_list->spinlock, flags);
715
716 list_add(&buf->list_item, &buf_list->list);
717 buf_list->count++;
718
719 spin_unlock_irqrestore(&buf_list->spinlock, flags);
720}
721
722/**
723 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
724 * @buf_list - pointer to buffer list
725 * @buf - pointer to buffer
726 */
727static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
728 struct n_hdlc_buf *buf)
729{
730 unsigned long flags;
731
732 spin_lock_irqsave(&buf_list->spinlock, flags);
733
734 list_add_tail(&buf->list_item, &buf_list->list);
735 buf_list->count++;
736
737 spin_unlock_irqrestore(&buf_list->spinlock, flags);
738} /* end of n_hdlc_buf_put() */
739
740/**
741 * n_hdlc_buf_get - remove and return an HDLC buffer from list
742 * @buf_list - pointer to HDLC buffer list
743 *
744 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
745 * list.
746 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
747 */
748static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
749{
750 unsigned long flags;
751 struct n_hdlc_buf *buf;
752
753 spin_lock_irqsave(&buf_list->spinlock, flags);
754
755 buf = list_first_entry_or_null(&buf_list->list,
756 struct n_hdlc_buf, list_item);
757 if (buf) {
758 list_del(&buf->list_item);
759 buf_list->count--;
760 }
761
762 spin_unlock_irqrestore(&buf_list->spinlock, flags);
763 return buf;
764} /* end of n_hdlc_buf_get() */
765
766static struct tty_ldisc_ops n_hdlc_ldisc = {
767 .owner = THIS_MODULE,
768 .magic = TTY_LDISC_MAGIC,
769 .name = "hdlc",
770 .open = n_hdlc_tty_open,
771 .close = n_hdlc_tty_close,
772 .read = n_hdlc_tty_read,
773 .write = n_hdlc_tty_write,
774 .ioctl = n_hdlc_tty_ioctl,
775 .poll = n_hdlc_tty_poll,
776 .receive_buf = n_hdlc_tty_receive,
777 .write_wakeup = n_hdlc_tty_wakeup,
778 .flush_buffer = flush_rx_queue,
779};
780
781static int __init n_hdlc_init(void)
782{
783 int status;
784
785 /* range check maxframe arg */
786 maxframe = clamp(maxframe, 4096, MAX_HDLC_FRAME_SIZE);
787
788 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
789 if (!status)
790 pr_info("N_HDLC line discipline registered with maxframe=%d\n",
791 maxframe);
792 else
793 pr_err("N_HDLC: error registering line discipline: %d\n",
794 status);
795
796 return status;
797
798} /* end of init_module() */
799
800static void __exit n_hdlc_exit(void)
801{
802 /* Release tty registration of line discipline */
803 int status = tty_unregister_ldisc(N_HDLC);
804
805 if (status)
806 pr_err("N_HDLC: can't unregister line discipline (err = %d)\n",
807 status);
808 else
809 pr_info("N_HDLC: line discipline unregistered\n");
810}
811
812module_init(n_hdlc_init);
813module_exit(n_hdlc_exit);
814
815MODULE_LICENSE("GPL");
816MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
817module_param(maxframe, int, 0);
818MODULE_ALIAS_LDISC(N_HDLC);
1// SPDX-License-Identifier: GPL-1.0+
2/* generic HDLC line discipline for Linux
3 *
4 * Written by Paul Fulghum paulkf@microgate.com
5 * for Microgate Corporation
6 *
7 * Microgate and SyncLink are registered trademarks of Microgate Corporation
8 *
9 * Adapted from ppp.c, written by Michael Callahan <callahan@maths.ox.ac.uk>,
10 * Al Longyear <longyear@netcom.com>,
11 * Paul Mackerras <Paul.Mackerras@cs.anu.edu.au>
12 *
13 * Original release 01/11/99
14 *
15 * This module implements the tty line discipline N_HDLC for use with
16 * tty device drivers that support bit-synchronous HDLC communications.
17 *
18 * All HDLC data is frame oriented which means:
19 *
20 * 1. tty write calls represent one complete transmit frame of data
21 * The device driver should accept the complete frame or none of
22 * the frame (busy) in the write method. Each write call should have
23 * a byte count in the range of 2-65535 bytes (2 is min HDLC frame
24 * with 1 addr byte and 1 ctrl byte). The max byte count of 65535
25 * should include any crc bytes required. For example, when using
26 * CCITT CRC32, 4 crc bytes are required, so the maximum size frame
27 * the application may transmit is limited to 65531 bytes. For CCITT
28 * CRC16, the maximum application frame size would be 65533.
29 *
30 *
31 * 2. receive callbacks from the device driver represents
32 * one received frame. The device driver should bypass
33 * the tty flip buffer and call the line discipline receive
34 * callback directly to avoid fragmenting or concatenating
35 * multiple frames into a single receive callback.
36 *
37 * The HDLC line discipline queues the receive frames in separate
38 * buffers so complete receive frames can be returned by the
39 * tty read calls.
40 *
41 * 3. tty read calls returns an entire frame of data or nothing.
42 *
43 * 4. all send and receive data is considered raw. No processing
44 * or translation is performed by the line discipline, regardless
45 * of the tty flags
46 *
47 * 5. When line discipline is queried for the amount of receive
48 * data available (FIOC), 0 is returned if no data available,
49 * otherwise the count of the next available frame is returned.
50 * (instead of the sum of all received frame counts).
51 *
52 * These conventions allow the standard tty programming interface
53 * to be used for synchronous HDLC applications when used with
54 * this line discipline (or another line discipline that is frame
55 * oriented such as N_PPP).
56 *
57 * The SyncLink driver (synclink.c) implements both asynchronous
58 * (using standard line discipline N_TTY) and synchronous HDLC
59 * (using N_HDLC) communications, with the latter using the above
60 * conventions.
61 *
62 * This implementation is very basic and does not maintain
63 * any statistics. The main point is to enforce the raw data
64 * and frame orientation of HDLC communications.
65 *
66 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
67 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
68 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
69 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
70 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
71 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
72 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
73 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
74 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
75 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
76 * OF THE POSSIBILITY OF SUCH DAMAGE.
77 */
78
79#define HDLC_MAGIC 0x239e
80
81#include <linux/module.h>
82#include <linux/init.h>
83#include <linux/kernel.h>
84#include <linux/sched.h>
85#include <linux/types.h>
86#include <linux/fcntl.h>
87#include <linux/interrupt.h>
88#include <linux/ptrace.h>
89
90#undef VERSION
91#define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
92
93#include <linux/poll.h>
94#include <linux/in.h>
95#include <linux/ioctl.h>
96#include <linux/slab.h>
97#include <linux/tty.h>
98#include <linux/errno.h>
99#include <linux/string.h> /* used in new tty drivers */
100#include <linux/signal.h> /* used in new tty drivers */
101#include <linux/if.h>
102#include <linux/bitops.h>
103
104#include <asm/termios.h>
105#include <linux/uaccess.h>
106
107/*
108 * Buffers for individual HDLC frames
109 */
110#define MAX_HDLC_FRAME_SIZE 65535
111#define DEFAULT_RX_BUF_COUNT 10
112#define MAX_RX_BUF_COUNT 60
113#define DEFAULT_TX_BUF_COUNT 3
114
115struct n_hdlc_buf {
116 struct list_head list_item;
117 int count;
118 char buf[1];
119};
120
121#define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
122
123struct n_hdlc_buf_list {
124 struct list_head list;
125 int count;
126 spinlock_t spinlock;
127};
128
129/**
130 * struct n_hdlc - per device instance data structure
131 * @magic - magic value for structure
132 * @flags - miscellaneous control flags
133 * @tty - ptr to TTY structure
134 * @backup_tty - TTY to use if tty gets closed
135 * @tbusy - reentrancy flag for tx wakeup code
136 * @woke_up - FIXME: describe this field
137 * @tx_buf_list - list of pending transmit frame buffers
138 * @rx_buf_list - list of received frame buffers
139 * @tx_free_buf_list - list unused transmit frame buffers
140 * @rx_free_buf_list - list unused received frame buffers
141 */
142struct n_hdlc {
143 int magic;
144 __u32 flags;
145 struct tty_struct *tty;
146 struct tty_struct *backup_tty;
147 int tbusy;
148 int woke_up;
149 struct n_hdlc_buf_list tx_buf_list;
150 struct n_hdlc_buf_list rx_buf_list;
151 struct n_hdlc_buf_list tx_free_buf_list;
152 struct n_hdlc_buf_list rx_free_buf_list;
153};
154
155/*
156 * HDLC buffer list manipulation functions
157 */
158static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
159 struct n_hdlc_buf *buf);
160static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
161 struct n_hdlc_buf *buf);
162static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
163
164/* Local functions */
165
166static struct n_hdlc *n_hdlc_alloc (void);
167
168/* debug level can be set by insmod for debugging purposes */
169#define DEBUG_LEVEL_INFO 1
170static int debuglevel;
171
172/* max frame size for memory allocations */
173static int maxframe = 4096;
174
175/* TTY callbacks */
176
177static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
178 __u8 __user *buf, size_t nr);
179static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
180 const unsigned char *buf, size_t nr);
181static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
182 unsigned int cmd, unsigned long arg);
183static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
184 poll_table *wait);
185static int n_hdlc_tty_open(struct tty_struct *tty);
186static void n_hdlc_tty_close(struct tty_struct *tty);
187static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
188 char *fp, int count);
189static void n_hdlc_tty_wakeup(struct tty_struct *tty);
190
191#define bset(p,b) ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
192
193#define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
194#define n_hdlc2tty(n_hdlc) ((n_hdlc)->tty)
195
196static void flush_rx_queue(struct tty_struct *tty)
197{
198 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
199 struct n_hdlc_buf *buf;
200
201 while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
202 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
203}
204
205static void flush_tx_queue(struct tty_struct *tty)
206{
207 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
208 struct n_hdlc_buf *buf;
209
210 while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
211 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
212}
213
214static struct tty_ldisc_ops n_hdlc_ldisc = {
215 .owner = THIS_MODULE,
216 .magic = TTY_LDISC_MAGIC,
217 .name = "hdlc",
218 .open = n_hdlc_tty_open,
219 .close = n_hdlc_tty_close,
220 .read = n_hdlc_tty_read,
221 .write = n_hdlc_tty_write,
222 .ioctl = n_hdlc_tty_ioctl,
223 .poll = n_hdlc_tty_poll,
224 .receive_buf = n_hdlc_tty_receive,
225 .write_wakeup = n_hdlc_tty_wakeup,
226 .flush_buffer = flush_rx_queue,
227};
228
229/**
230 * n_hdlc_release - release an n_hdlc per device line discipline info structure
231 * @n_hdlc - per device line discipline info structure
232 */
233static void n_hdlc_release(struct n_hdlc *n_hdlc)
234{
235 struct tty_struct *tty = n_hdlc2tty (n_hdlc);
236 struct n_hdlc_buf *buf;
237
238 if (debuglevel >= DEBUG_LEVEL_INFO)
239 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
240
241 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
242 wake_up_interruptible (&tty->read_wait);
243 wake_up_interruptible (&tty->write_wait);
244
245 if (tty->disc_data == n_hdlc)
246 tty->disc_data = NULL; /* Break the tty->n_hdlc link */
247
248 /* Release transmit and receive buffers */
249 for(;;) {
250 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
251 if (buf) {
252 kfree(buf);
253 } else
254 break;
255 }
256 for(;;) {
257 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
258 if (buf) {
259 kfree(buf);
260 } else
261 break;
262 }
263 for(;;) {
264 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
265 if (buf) {
266 kfree(buf);
267 } else
268 break;
269 }
270 for(;;) {
271 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
272 if (buf) {
273 kfree(buf);
274 } else
275 break;
276 }
277 kfree(n_hdlc);
278
279} /* end of n_hdlc_release() */
280
281/**
282 * n_hdlc_tty_close - line discipline close
283 * @tty - pointer to tty info structure
284 *
285 * Called when the line discipline is changed to something
286 * else, the tty is closed, or the tty detects a hangup.
287 */
288static void n_hdlc_tty_close(struct tty_struct *tty)
289{
290 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
291
292 if (debuglevel >= DEBUG_LEVEL_INFO)
293 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
294
295 if (n_hdlc != NULL) {
296 if (n_hdlc->magic != HDLC_MAGIC) {
297 printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
298 return;
299 }
300#if defined(TTY_NO_WRITE_SPLIT)
301 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
302#endif
303 tty->disc_data = NULL;
304 if (tty == n_hdlc->backup_tty)
305 n_hdlc->backup_tty = NULL;
306 if (tty != n_hdlc->tty)
307 return;
308 if (n_hdlc->backup_tty) {
309 n_hdlc->tty = n_hdlc->backup_tty;
310 } else {
311 n_hdlc_release (n_hdlc);
312 }
313 }
314
315 if (debuglevel >= DEBUG_LEVEL_INFO)
316 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
317
318} /* end of n_hdlc_tty_close() */
319
320/**
321 * n_hdlc_tty_open - called when line discipline changed to n_hdlc
322 * @tty - pointer to tty info structure
323 *
324 * Returns 0 if success, otherwise error code
325 */
326static int n_hdlc_tty_open (struct tty_struct *tty)
327{
328 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
329
330 if (debuglevel >= DEBUG_LEVEL_INFO)
331 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
332 __FILE__,__LINE__,
333 tty->name);
334
335 /* There should not be an existing table for this slot. */
336 if (n_hdlc) {
337 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
338 return -EEXIST;
339 }
340
341 n_hdlc = n_hdlc_alloc();
342 if (!n_hdlc) {
343 printk (KERN_ERR "n_hdlc_alloc failed\n");
344 return -ENFILE;
345 }
346
347 tty->disc_data = n_hdlc;
348 n_hdlc->tty = tty;
349 tty->receive_room = 65536;
350
351#if defined(TTY_NO_WRITE_SPLIT)
352 /* change tty_io write() to not split large writes into 8K chunks */
353 set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
354#endif
355
356 /* flush receive data from driver */
357 tty_driver_flush_buffer(tty);
358
359 if (debuglevel >= DEBUG_LEVEL_INFO)
360 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
361
362 return 0;
363
364} /* end of n_tty_hdlc_open() */
365
366/**
367 * n_hdlc_send_frames - send frames on pending send buffer list
368 * @n_hdlc - pointer to ldisc instance data
369 * @tty - pointer to tty instance data
370 *
371 * Send frames on pending send buffer list until the driver does not accept a
372 * frame (busy) this function is called after adding a frame to the send buffer
373 * list and by the tty wakeup callback.
374 */
375static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
376{
377 register int actual;
378 unsigned long flags;
379 struct n_hdlc_buf *tbuf;
380
381 if (debuglevel >= DEBUG_LEVEL_INFO)
382 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
383 check_again:
384
385 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
386 if (n_hdlc->tbusy) {
387 n_hdlc->woke_up = 1;
388 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
389 return;
390 }
391 n_hdlc->tbusy = 1;
392 n_hdlc->woke_up = 0;
393 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
394
395 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
396 while (tbuf) {
397 if (debuglevel >= DEBUG_LEVEL_INFO)
398 printk("%s(%d)sending frame %p, count=%d\n",
399 __FILE__,__LINE__,tbuf,tbuf->count);
400
401 /* Send the next block of data to device */
402 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
403 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
404
405 /* rollback was possible and has been done */
406 if (actual == -ERESTARTSYS) {
407 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
408 break;
409 }
410 /* if transmit error, throw frame away by */
411 /* pretending it was accepted by driver */
412 if (actual < 0)
413 actual = tbuf->count;
414
415 if (actual == tbuf->count) {
416 if (debuglevel >= DEBUG_LEVEL_INFO)
417 printk("%s(%d)frame %p completed\n",
418 __FILE__,__LINE__,tbuf);
419
420 /* free current transmit buffer */
421 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
422
423 /* wait up sleeping writers */
424 wake_up_interruptible(&tty->write_wait);
425
426 /* get next pending transmit buffer */
427 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
428 } else {
429 if (debuglevel >= DEBUG_LEVEL_INFO)
430 printk("%s(%d)frame %p pending\n",
431 __FILE__,__LINE__,tbuf);
432
433 /*
434 * the buffer was not accepted by driver,
435 * return it back into tx queue
436 */
437 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
438 break;
439 }
440 }
441
442 if (!tbuf)
443 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
444
445 /* Clear the re-entry flag */
446 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
447 n_hdlc->tbusy = 0;
448 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
449
450 if (n_hdlc->woke_up)
451 goto check_again;
452
453 if (debuglevel >= DEBUG_LEVEL_INFO)
454 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
455
456} /* end of n_hdlc_send_frames() */
457
458/**
459 * n_hdlc_tty_wakeup - Callback for transmit wakeup
460 * @tty - pointer to associated tty instance data
461 *
462 * Called when low level device driver can accept more send data.
463 */
464static void n_hdlc_tty_wakeup(struct tty_struct *tty)
465{
466 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
467
468 if (debuglevel >= DEBUG_LEVEL_INFO)
469 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
470
471 if (!n_hdlc)
472 return;
473
474 if (tty != n_hdlc->tty) {
475 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
476 return;
477 }
478
479 n_hdlc_send_frames (n_hdlc, tty);
480
481} /* end of n_hdlc_tty_wakeup() */
482
483/**
484 * n_hdlc_tty_receive - Called by tty driver when receive data is available
485 * @tty - pointer to tty instance data
486 * @data - pointer to received data
487 * @flags - pointer to flags for data
488 * @count - count of received data in bytes
489 *
490 * Called by tty low level driver when receive data is available. Data is
491 * interpreted as one HDLC frame.
492 */
493static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
494 char *flags, int count)
495{
496 register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
497 register struct n_hdlc_buf *buf;
498
499 if (debuglevel >= DEBUG_LEVEL_INFO)
500 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
501 __FILE__,__LINE__, count);
502
503 /* This can happen if stuff comes in on the backup tty */
504 if (!n_hdlc || tty != n_hdlc->tty)
505 return;
506
507 /* verify line is using HDLC discipline */
508 if (n_hdlc->magic != HDLC_MAGIC) {
509 printk("%s(%d) line not using HDLC discipline\n",
510 __FILE__,__LINE__);
511 return;
512 }
513
514 if ( count>maxframe ) {
515 if (debuglevel >= DEBUG_LEVEL_INFO)
516 printk("%s(%d) rx count>maxframesize, data discarded\n",
517 __FILE__,__LINE__);
518 return;
519 }
520
521 /* get a free HDLC buffer */
522 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
523 if (!buf) {
524 /* no buffers in free list, attempt to allocate another rx buffer */
525 /* unless the maximum count has been reached */
526 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
527 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
528 }
529
530 if (!buf) {
531 if (debuglevel >= DEBUG_LEVEL_INFO)
532 printk("%s(%d) no more rx buffers, data discarded\n",
533 __FILE__,__LINE__);
534 return;
535 }
536
537 /* copy received data to HDLC buffer */
538 memcpy(buf->buf,data,count);
539 buf->count=count;
540
541 /* add HDLC buffer to list of received frames */
542 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
543
544 /* wake up any blocked reads and perform async signalling */
545 wake_up_interruptible (&tty->read_wait);
546 if (n_hdlc->tty->fasync != NULL)
547 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
548
549} /* end of n_hdlc_tty_receive() */
550
551/**
552 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
553 * @tty - pointer to tty instance data
554 * @file - pointer to open file object
555 * @buf - pointer to returned data buffer
556 * @nr - size of returned data buffer
557 *
558 * Returns the number of bytes returned or error code.
559 */
560static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
561 __u8 __user *buf, size_t nr)
562{
563 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
564 int ret = 0;
565 struct n_hdlc_buf *rbuf;
566 DECLARE_WAITQUEUE(wait, current);
567
568 if (debuglevel >= DEBUG_LEVEL_INFO)
569 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
570
571 /* Validate the pointers */
572 if (!n_hdlc)
573 return -EIO;
574
575 /* verify user access to buffer */
576 if (!access_ok(VERIFY_WRITE, buf, nr)) {
577 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
578 "buffer\n", __FILE__, __LINE__);
579 return -EFAULT;
580 }
581
582 add_wait_queue(&tty->read_wait, &wait);
583
584 for (;;) {
585 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
586 ret = -EIO;
587 break;
588 }
589 if (tty_hung_up_p(file))
590 break;
591
592 set_current_state(TASK_INTERRUPTIBLE);
593
594 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
595 if (rbuf) {
596 if (rbuf->count > nr) {
597 /* too large for caller's buffer */
598 ret = -EOVERFLOW;
599 } else {
600 if (copy_to_user(buf, rbuf->buf, rbuf->count))
601 ret = -EFAULT;
602 else
603 ret = rbuf->count;
604 }
605
606 if (n_hdlc->rx_free_buf_list.count >
607 DEFAULT_RX_BUF_COUNT)
608 kfree(rbuf);
609 else
610 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
611 break;
612 }
613
614 /* no data */
615 if (file->f_flags & O_NONBLOCK) {
616 ret = -EAGAIN;
617 break;
618 }
619
620 schedule();
621
622 if (signal_pending(current)) {
623 ret = -EINTR;
624 break;
625 }
626 }
627
628 remove_wait_queue(&tty->read_wait, &wait);
629 __set_current_state(TASK_RUNNING);
630
631 return ret;
632
633} /* end of n_hdlc_tty_read() */
634
635/**
636 * n_hdlc_tty_write - write a single frame of data to device
637 * @tty - pointer to associated tty device instance data
638 * @file - pointer to file object data
639 * @data - pointer to transmit data (one frame)
640 * @count - size of transmit frame in bytes
641 *
642 * Returns the number of bytes written (or error code).
643 */
644static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
645 const unsigned char *data, size_t count)
646{
647 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
648 int error = 0;
649 DECLARE_WAITQUEUE(wait, current);
650 struct n_hdlc_buf *tbuf;
651
652 if (debuglevel >= DEBUG_LEVEL_INFO)
653 printk("%s(%d)n_hdlc_tty_write() called count=%zd\n",
654 __FILE__,__LINE__,count);
655
656 /* Verify pointers */
657 if (!n_hdlc)
658 return -EIO;
659
660 if (n_hdlc->magic != HDLC_MAGIC)
661 return -EIO;
662
663 /* verify frame size */
664 if (count > maxframe ) {
665 if (debuglevel & DEBUG_LEVEL_INFO)
666 printk (KERN_WARNING
667 "n_hdlc_tty_write: truncating user packet "
668 "from %lu to %d\n", (unsigned long) count,
669 maxframe );
670 count = maxframe;
671 }
672
673 add_wait_queue(&tty->write_wait, &wait);
674
675 for (;;) {
676 set_current_state(TASK_INTERRUPTIBLE);
677
678 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
679 if (tbuf)
680 break;
681
682 if (file->f_flags & O_NONBLOCK) {
683 error = -EAGAIN;
684 break;
685 }
686 schedule();
687
688 n_hdlc = tty2n_hdlc (tty);
689 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
690 tty != n_hdlc->tty) {
691 printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
692 error = -EIO;
693 break;
694 }
695
696 if (signal_pending(current)) {
697 error = -EINTR;
698 break;
699 }
700 }
701
702 __set_current_state(TASK_RUNNING);
703 remove_wait_queue(&tty->write_wait, &wait);
704
705 if (!error) {
706 /* Retrieve the user's buffer */
707 memcpy(tbuf->buf, data, count);
708
709 /* Send the data */
710 tbuf->count = error = count;
711 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
712 n_hdlc_send_frames(n_hdlc,tty);
713 }
714
715 return error;
716
717} /* end of n_hdlc_tty_write() */
718
719/**
720 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
721 * @tty - pointer to tty instance data
722 * @file - pointer to open file object for device
723 * @cmd - IOCTL command code
724 * @arg - argument for IOCTL call (cmd dependent)
725 *
726 * Returns command dependent result.
727 */
728static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
729 unsigned int cmd, unsigned long arg)
730{
731 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
732 int error = 0;
733 int count;
734 unsigned long flags;
735 struct n_hdlc_buf *buf = NULL;
736
737 if (debuglevel >= DEBUG_LEVEL_INFO)
738 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
739 __FILE__,__LINE__,cmd);
740
741 /* Verify the status of the device */
742 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
743 return -EBADF;
744
745 switch (cmd) {
746 case FIONREAD:
747 /* report count of read data available */
748 /* in next available frame (if any) */
749 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
750 buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
751 struct n_hdlc_buf, list_item);
752 if (buf)
753 count = buf->count;
754 else
755 count = 0;
756 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
757 error = put_user(count, (int __user *)arg);
758 break;
759
760 case TIOCOUTQ:
761 /* get the pending tx byte count in the driver */
762 count = tty_chars_in_buffer(tty);
763 /* add size of next output frame in queue */
764 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
765 buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
766 struct n_hdlc_buf, list_item);
767 if (buf)
768 count += buf->count;
769 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
770 error = put_user(count, (int __user *)arg);
771 break;
772
773 case TCFLSH:
774 switch (arg) {
775 case TCIOFLUSH:
776 case TCOFLUSH:
777 flush_tx_queue(tty);
778 }
779 /* fall through to default */
780
781 default:
782 error = n_tty_ioctl_helper(tty, file, cmd, arg);
783 break;
784 }
785 return error;
786
787} /* end of n_hdlc_tty_ioctl() */
788
789/**
790 * n_hdlc_tty_poll - TTY callback for poll system call
791 * @tty - pointer to tty instance data
792 * @filp - pointer to open file object for device
793 * @poll_table - wait queue for operations
794 *
795 * Determine which operations (read/write) will not block and return info
796 * to caller.
797 * Returns a bit mask containing info on which ops will not block.
798 */
799static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
800 poll_table *wait)
801{
802 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
803 __poll_t mask = 0;
804
805 if (debuglevel >= DEBUG_LEVEL_INFO)
806 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
807
808 if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
809 /* queue current process into any wait queue that */
810 /* may awaken in the future (read and write) */
811
812 poll_wait(filp, &tty->read_wait, wait);
813 poll_wait(filp, &tty->write_wait, wait);
814
815 /* set bits for operations that won't block */
816 if (!list_empty(&n_hdlc->rx_buf_list.list))
817 mask |= EPOLLIN | EPOLLRDNORM; /* readable */
818 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
819 mask |= EPOLLHUP;
820 if (tty_hung_up_p(filp))
821 mask |= EPOLLHUP;
822 if (!tty_is_writelocked(tty) &&
823 !list_empty(&n_hdlc->tx_free_buf_list.list))
824 mask |= EPOLLOUT | EPOLLWRNORM; /* writable */
825 }
826 return mask;
827} /* end of n_hdlc_tty_poll() */
828
829/**
830 * n_hdlc_alloc - allocate an n_hdlc instance data structure
831 *
832 * Returns a pointer to newly created structure if success, otherwise %NULL
833 */
834static struct n_hdlc *n_hdlc_alloc(void)
835{
836 struct n_hdlc_buf *buf;
837 int i;
838 struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL);
839
840 if (!n_hdlc)
841 return NULL;
842
843 spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);
844 spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
845 spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
846 spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
847
848 INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);
849 INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);
850 INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);
851 INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);
852
853 /* allocate free rx buffer list */
854 for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
855 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
856 if (buf)
857 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
858 else if (debuglevel >= DEBUG_LEVEL_INFO)
859 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
860 }
861
862 /* allocate free tx buffer list */
863 for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
864 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
865 if (buf)
866 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
867 else if (debuglevel >= DEBUG_LEVEL_INFO)
868 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
869 }
870
871 /* Initialize the control block */
872 n_hdlc->magic = HDLC_MAGIC;
873 n_hdlc->flags = 0;
874
875 return n_hdlc;
876
877} /* end of n_hdlc_alloc() */
878
879/**
880 * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
881 * @buf_list - pointer to the buffer list
882 * @buf - pointer to the buffer
883 */
884static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
885 struct n_hdlc_buf *buf)
886{
887 unsigned long flags;
888
889 spin_lock_irqsave(&buf_list->spinlock, flags);
890
891 list_add(&buf->list_item, &buf_list->list);
892 buf_list->count++;
893
894 spin_unlock_irqrestore(&buf_list->spinlock, flags);
895}
896
897/**
898 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
899 * @buf_list - pointer to buffer list
900 * @buf - pointer to buffer
901 */
902static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
903 struct n_hdlc_buf *buf)
904{
905 unsigned long flags;
906
907 spin_lock_irqsave(&buf_list->spinlock, flags);
908
909 list_add_tail(&buf->list_item, &buf_list->list);
910 buf_list->count++;
911
912 spin_unlock_irqrestore(&buf_list->spinlock, flags);
913} /* end of n_hdlc_buf_put() */
914
915/**
916 * n_hdlc_buf_get - remove and return an HDLC buffer from list
917 * @buf_list - pointer to HDLC buffer list
918 *
919 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
920 * list.
921 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
922 */
923static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
924{
925 unsigned long flags;
926 struct n_hdlc_buf *buf;
927
928 spin_lock_irqsave(&buf_list->spinlock, flags);
929
930 buf = list_first_entry_or_null(&buf_list->list,
931 struct n_hdlc_buf, list_item);
932 if (buf) {
933 list_del(&buf->list_item);
934 buf_list->count--;
935 }
936
937 spin_unlock_irqrestore(&buf_list->spinlock, flags);
938 return buf;
939} /* end of n_hdlc_buf_get() */
940
941static const char hdlc_banner[] __initconst =
942 KERN_INFO "HDLC line discipline maxframe=%u\n";
943static const char hdlc_register_ok[] __initconst =
944 KERN_INFO "N_HDLC line discipline registered.\n";
945static const char hdlc_register_fail[] __initconst =
946 KERN_ERR "error registering line discipline: %d\n";
947
948static int __init n_hdlc_init(void)
949{
950 int status;
951
952 /* range check maxframe arg */
953 if (maxframe < 4096)
954 maxframe = 4096;
955 else if (maxframe > 65535)
956 maxframe = 65535;
957
958 printk(hdlc_banner, maxframe);
959
960 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
961 if (!status)
962 printk(hdlc_register_ok);
963 else
964 printk(hdlc_register_fail, status);
965
966 return status;
967
968} /* end of init_module() */
969
970static const char hdlc_unregister_ok[] __exitdata =
971 KERN_INFO "N_HDLC: line discipline unregistered\n";
972static const char hdlc_unregister_fail[] __exitdata =
973 KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
974
975static void __exit n_hdlc_exit(void)
976{
977 /* Release tty registration of line discipline */
978 int status = tty_unregister_ldisc(N_HDLC);
979
980 if (status)
981 printk(hdlc_unregister_fail, status);
982 else
983 printk(hdlc_unregister_ok);
984}
985
986module_init(n_hdlc_init);
987module_exit(n_hdlc_exit);
988
989MODULE_LICENSE("GPL");
990MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
991module_param(debuglevel, int, 0);
992module_param(maxframe, int, 0);
993MODULE_ALIAS_LDISC(N_HDLC);