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