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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#include <linux/module.h>
80#include <linux/init.h>
81#include <linux/kernel.h>
82#include <linux/sched.h>
83#include <linux/types.h>
84#include <linux/fcntl.h>
85#include <linux/interrupt.h>
86#include <linux/ptrace.h>
87
88#include <linux/poll.h>
89#include <linux/in.h>
90#include <linux/ioctl.h>
91#include <linux/slab.h>
92#include <linux/tty.h>
93#include <linux/errno.h>
94#include <linux/string.h> /* used in new tty drivers */
95#include <linux/signal.h> /* used in new tty drivers */
96#include <linux/if.h>
97#include <linux/bitops.h>
98
99#include <linux/uaccess.h>
100#include "tty.h"
101
102/*
103 * Buffers for individual HDLC frames
104 */
105#define MAX_HDLC_FRAME_SIZE 65535
106#define DEFAULT_RX_BUF_COUNT 10
107#define MAX_RX_BUF_COUNT 60
108#define DEFAULT_TX_BUF_COUNT 3
109
110struct n_hdlc_buf {
111 struct list_head list_item;
112 size_t count;
113 u8 buf[];
114};
115
116struct n_hdlc_buf_list {
117 struct list_head list;
118 int count;
119 spinlock_t spinlock;
120};
121
122/**
123 * struct n_hdlc - per device instance data structure
124 * @tbusy: reentrancy flag for tx wakeup code
125 * @woke_up: tx wakeup needs to be run again as it was called while @tbusy
126 * @tx_buf_list: list of pending transmit frame buffers
127 * @rx_buf_list: list of received frame buffers
128 * @tx_free_buf_list: list unused transmit frame buffers
129 * @rx_free_buf_list: list unused received frame buffers
130 */
131struct n_hdlc {
132 bool tbusy;
133 bool woke_up;
134 struct n_hdlc_buf_list tx_buf_list;
135 struct n_hdlc_buf_list rx_buf_list;
136 struct n_hdlc_buf_list tx_free_buf_list;
137 struct n_hdlc_buf_list rx_free_buf_list;
138 struct work_struct write_work;
139 struct tty_struct *tty_for_write_work;
140};
141
142/*
143 * HDLC buffer list manipulation functions
144 */
145static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
146 struct n_hdlc_buf *buf);
147static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
148 struct n_hdlc_buf *buf);
149static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
150
151/* Local functions */
152
153static struct n_hdlc *n_hdlc_alloc(void);
154static void n_hdlc_tty_write_work(struct work_struct *work);
155
156/* max frame size for memory allocations */
157static int maxframe = 4096;
158
159static void flush_rx_queue(struct tty_struct *tty)
160{
161 struct n_hdlc *n_hdlc = tty->disc_data;
162 struct n_hdlc_buf *buf;
163
164 while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
165 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
166}
167
168static void flush_tx_queue(struct tty_struct *tty)
169{
170 struct n_hdlc *n_hdlc = tty->disc_data;
171 struct n_hdlc_buf *buf;
172
173 while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
174 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
175}
176
177static void n_hdlc_free_buf_list(struct n_hdlc_buf_list *list)
178{
179 struct n_hdlc_buf *buf;
180
181 do {
182 buf = n_hdlc_buf_get(list);
183 kfree(buf);
184 } while (buf);
185}
186
187/**
188 * n_hdlc_tty_close - line discipline close
189 * @tty: pointer to tty info structure
190 *
191 * Called when the line discipline is changed to something
192 * else, the tty is closed, or the tty detects a hangup.
193 */
194static void n_hdlc_tty_close(struct tty_struct *tty)
195{
196 struct n_hdlc *n_hdlc = tty->disc_data;
197
198#if defined(TTY_NO_WRITE_SPLIT)
199 clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags);
200#endif
201 tty->disc_data = NULL;
202
203 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
204 wake_up_interruptible(&tty->read_wait);
205 wake_up_interruptible(&tty->write_wait);
206
207 cancel_work_sync(&n_hdlc->write_work);
208
209 n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list);
210 n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list);
211 n_hdlc_free_buf_list(&n_hdlc->rx_buf_list);
212 n_hdlc_free_buf_list(&n_hdlc->tx_buf_list);
213 kfree(n_hdlc);
214} /* end of n_hdlc_tty_close() */
215
216/**
217 * n_hdlc_tty_open - called when line discipline changed to n_hdlc
218 * @tty: pointer to tty info structure
219 *
220 * Returns 0 if success, otherwise error code
221 */
222static int n_hdlc_tty_open(struct tty_struct *tty)
223{
224 struct n_hdlc *n_hdlc = tty->disc_data;
225
226 pr_debug("%s() called (device=%s)\n", __func__, tty->name);
227
228 /* There should not be an existing table for this slot. */
229 if (n_hdlc) {
230 pr_err("%s: tty already associated!\n", __func__);
231 return -EEXIST;
232 }
233
234 n_hdlc = n_hdlc_alloc();
235 if (!n_hdlc) {
236 pr_err("%s: n_hdlc_alloc failed\n", __func__);
237 return -ENFILE;
238 }
239
240 INIT_WORK(&n_hdlc->write_work, n_hdlc_tty_write_work);
241 n_hdlc->tty_for_write_work = tty;
242 tty->disc_data = n_hdlc;
243 tty->receive_room = 65536;
244
245 /* change tty_io write() to not split large writes into 8K chunks */
246 set_bit(TTY_NO_WRITE_SPLIT, &tty->flags);
247
248 /* flush receive data from driver */
249 tty_driver_flush_buffer(tty);
250
251 return 0;
252
253} /* end of n_tty_hdlc_open() */
254
255/**
256 * n_hdlc_send_frames - send frames on pending send buffer list
257 * @n_hdlc: pointer to ldisc instance data
258 * @tty: pointer to tty instance data
259 *
260 * Send frames on pending send buffer list until the driver does not accept a
261 * frame (busy) this function is called after adding a frame to the send buffer
262 * list and by the tty wakeup callback.
263 */
264static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
265{
266 unsigned long flags;
267 struct n_hdlc_buf *tbuf;
268 ssize_t actual;
269
270check_again:
271
272 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
273 if (n_hdlc->tbusy) {
274 n_hdlc->woke_up = true;
275 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
276 return;
277 }
278 n_hdlc->tbusy = true;
279 n_hdlc->woke_up = false;
280 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
281
282 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
283 while (tbuf) {
284 pr_debug("sending frame %p, count=%zu\n", tbuf, tbuf->count);
285
286 /* Send the next block of data to device */
287 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
288 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
289
290 /* rollback was possible and has been done */
291 if (actual == -ERESTARTSYS) {
292 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
293 break;
294 }
295 /* if transmit error, throw frame away by */
296 /* pretending it was accepted by driver */
297 if (actual < 0)
298 actual = tbuf->count;
299
300 if (actual == tbuf->count) {
301 pr_debug("frame %p completed\n", tbuf);
302
303 /* free current transmit buffer */
304 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
305
306 /* wait up sleeping writers */
307 wake_up_interruptible(&tty->write_wait);
308
309 /* get next pending transmit buffer */
310 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
311 } else {
312 pr_debug("frame %p pending\n", tbuf);
313
314 /*
315 * the buffer was not accepted by driver,
316 * return it back into tx queue
317 */
318 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
319 break;
320 }
321 }
322
323 if (!tbuf)
324 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
325
326 /* Clear the re-entry flag */
327 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
328 n_hdlc->tbusy = false;
329 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
330
331 if (n_hdlc->woke_up)
332 goto check_again;
333} /* end of n_hdlc_send_frames() */
334
335/**
336 * n_hdlc_tty_write_work - Asynchronous callback for transmit wakeup
337 * @work: pointer to work_struct
338 *
339 * Called when low level device driver can accept more send data.
340 */
341static void n_hdlc_tty_write_work(struct work_struct *work)
342{
343 struct n_hdlc *n_hdlc = container_of(work, struct n_hdlc, write_work);
344 struct tty_struct *tty = n_hdlc->tty_for_write_work;
345
346 n_hdlc_send_frames(n_hdlc, tty);
347} /* end of n_hdlc_tty_write_work() */
348
349/**
350 * n_hdlc_tty_wakeup - Callback for transmit wakeup
351 * @tty: pointer to associated tty instance data
352 *
353 * Called when low level device driver can accept more send data.
354 */
355static void n_hdlc_tty_wakeup(struct tty_struct *tty)
356{
357 struct n_hdlc *n_hdlc = tty->disc_data;
358
359 schedule_work(&n_hdlc->write_work);
360} /* end of n_hdlc_tty_wakeup() */
361
362/**
363 * n_hdlc_tty_receive - Called by tty driver when receive data is available
364 * @tty: pointer to tty instance data
365 * @data: pointer to received data
366 * @flags: pointer to flags for data
367 * @count: count of received data in bytes
368 *
369 * Called by tty low level driver when receive data is available. Data is
370 * interpreted as one HDLC frame.
371 */
372static void n_hdlc_tty_receive(struct tty_struct *tty, const u8 *data,
373 const u8 *flags, size_t count)
374{
375 register struct n_hdlc *n_hdlc = tty->disc_data;
376 register struct n_hdlc_buf *buf;
377
378 pr_debug("%s() called count=%zu\n", __func__, count);
379
380 if (count > maxframe) {
381 pr_debug("rx count>maxframesize, data discarded\n");
382 return;
383 }
384
385 /* get a free HDLC buffer */
386 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
387 if (!buf) {
388 /*
389 * no buffers in free list, attempt to allocate another rx
390 * buffer unless the maximum count has been reached
391 */
392 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
393 buf = kmalloc(struct_size(buf, buf, maxframe),
394 GFP_ATOMIC);
395 }
396
397 if (!buf) {
398 pr_debug("no more rx buffers, data discarded\n");
399 return;
400 }
401
402 /* copy received data to HDLC buffer */
403 memcpy(buf->buf, data, count);
404 buf->count = count;
405
406 /* add HDLC buffer to list of received frames */
407 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
408
409 /* wake up any blocked reads and perform async signalling */
410 wake_up_interruptible(&tty->read_wait);
411 if (tty->fasync != NULL)
412 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
413
414} /* end of n_hdlc_tty_receive() */
415
416/**
417 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
418 * @tty: pointer to tty instance data
419 * @file: pointer to open file object
420 * @kbuf: pointer to returned data buffer
421 * @nr: size of returned data buffer
422 * @cookie: stored rbuf from previous run
423 * @offset: offset into the data buffer
424 *
425 * Returns the number of bytes returned or error code.
426 */
427static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
428 u8 *kbuf, size_t nr, void **cookie,
429 unsigned long offset)
430{
431 struct n_hdlc *n_hdlc = tty->disc_data;
432 int ret = 0;
433 struct n_hdlc_buf *rbuf;
434 DECLARE_WAITQUEUE(wait, current);
435
436 /* Is this a repeated call for an rbuf we already found earlier? */
437 rbuf = *cookie;
438 if (rbuf)
439 goto have_rbuf;
440
441 add_wait_queue(&tty->read_wait, &wait);
442
443 for (;;) {
444 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
445 ret = -EIO;
446 break;
447 }
448 if (tty_hung_up_p(file))
449 break;
450
451 set_current_state(TASK_INTERRUPTIBLE);
452
453 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
454 if (rbuf)
455 break;
456
457 /* no data */
458 if (tty_io_nonblock(tty, file)) {
459 ret = -EAGAIN;
460 break;
461 }
462
463 schedule();
464
465 if (signal_pending(current)) {
466 ret = -EINTR;
467 break;
468 }
469 }
470
471 remove_wait_queue(&tty->read_wait, &wait);
472 __set_current_state(TASK_RUNNING);
473
474 if (!rbuf)
475 return ret;
476 *cookie = rbuf;
477
478have_rbuf:
479 /* Have we used it up entirely? */
480 if (offset >= rbuf->count)
481 goto done_with_rbuf;
482
483 /* More data to go, but can't copy any more? EOVERFLOW */
484 ret = -EOVERFLOW;
485 if (!nr)
486 goto done_with_rbuf;
487
488 /* Copy as much data as possible */
489 ret = rbuf->count - offset;
490 if (ret > nr)
491 ret = nr;
492 memcpy(kbuf, rbuf->buf+offset, ret);
493 offset += ret;
494
495 /* If we still have data left, we leave the rbuf in the cookie */
496 if (offset < rbuf->count)
497 return ret;
498
499done_with_rbuf:
500 *cookie = NULL;
501
502 if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
503 kfree(rbuf);
504 else
505 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
506
507 return ret;
508
509} /* end of n_hdlc_tty_read() */
510
511/**
512 * n_hdlc_tty_write - write a single frame of data to device
513 * @tty: pointer to associated tty device instance data
514 * @file: pointer to file object data
515 * @data: pointer to transmit data (one frame)
516 * @count: size of transmit frame in bytes
517 *
518 * Returns the number of bytes written (or error code).
519 */
520static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
521 const u8 *data, size_t count)
522{
523 struct n_hdlc *n_hdlc = tty->disc_data;
524 DECLARE_WAITQUEUE(wait, current);
525 struct n_hdlc_buf *tbuf;
526 ssize_t error = 0;
527
528 pr_debug("%s() called count=%zd\n", __func__, count);
529
530 /* verify frame size */
531 if (count > maxframe) {
532 pr_debug("%s: truncating user packet from %zu to %d\n",
533 __func__, count, maxframe);
534 count = maxframe;
535 }
536
537 add_wait_queue(&tty->write_wait, &wait);
538
539 for (;;) {
540 set_current_state(TASK_INTERRUPTIBLE);
541
542 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
543 if (tbuf)
544 break;
545
546 if (tty_io_nonblock(tty, file)) {
547 error = -EAGAIN;
548 break;
549 }
550 schedule();
551
552 if (signal_pending(current)) {
553 error = -EINTR;
554 break;
555 }
556 }
557
558 __set_current_state(TASK_RUNNING);
559 remove_wait_queue(&tty->write_wait, &wait);
560
561 if (!error) {
562 /* Retrieve the user's buffer */
563 memcpy(tbuf->buf, data, count);
564
565 /* Send the data */
566 tbuf->count = error = count;
567 n_hdlc_buf_put(&n_hdlc->tx_buf_list, tbuf);
568 n_hdlc_send_frames(n_hdlc, tty);
569 }
570
571 return error;
572
573} /* end of n_hdlc_tty_write() */
574
575/**
576 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
577 * @tty: pointer to tty instance data
578 * @cmd: IOCTL command code
579 * @arg: argument for IOCTL call (cmd dependent)
580 *
581 * Returns command dependent result.
582 */
583static int n_hdlc_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
584 unsigned long arg)
585{
586 struct n_hdlc *n_hdlc = tty->disc_data;
587 int error = 0;
588 int count;
589 unsigned long flags;
590 struct n_hdlc_buf *buf = NULL;
591
592 pr_debug("%s() called %d\n", __func__, cmd);
593
594 switch (cmd) {
595 case FIONREAD:
596 /* report count of read data available */
597 /* in next available frame (if any) */
598 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags);
599 buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
600 struct n_hdlc_buf, list_item);
601 if (buf)
602 count = buf->count;
603 else
604 count = 0;
605 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags);
606 error = put_user(count, (int __user *)arg);
607 break;
608
609 case TIOCOUTQ:
610 /* get the pending tx byte count in the driver */
611 count = tty_chars_in_buffer(tty);
612 /* add size of next output frame in queue */
613 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
614 buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
615 struct n_hdlc_buf, list_item);
616 if (buf)
617 count += buf->count;
618 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
619 error = put_user(count, (int __user *)arg);
620 break;
621
622 case TCFLSH:
623 switch (arg) {
624 case TCIOFLUSH:
625 case TCOFLUSH:
626 flush_tx_queue(tty);
627 }
628 fallthrough; /* to default */
629
630 default:
631 error = n_tty_ioctl_helper(tty, cmd, arg);
632 break;
633 }
634 return error;
635
636} /* end of n_hdlc_tty_ioctl() */
637
638/**
639 * n_hdlc_tty_poll - TTY callback for poll system call
640 * @tty: pointer to tty instance data
641 * @filp: pointer to open file object for device
642 * @wait: wait queue for operations
643 *
644 * Determine which operations (read/write) will not block and return info
645 * to caller.
646 * Returns a bit mask containing info on which ops will not block.
647 */
648static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
649 poll_table *wait)
650{
651 struct n_hdlc *n_hdlc = tty->disc_data;
652 __poll_t mask = 0;
653
654 /*
655 * queue the current process into any wait queue that may awaken in the
656 * future (read and write)
657 */
658 poll_wait(filp, &tty->read_wait, wait);
659 poll_wait(filp, &tty->write_wait, wait);
660
661 /* set bits for operations that won't block */
662 if (!list_empty(&n_hdlc->rx_buf_list.list))
663 mask |= EPOLLIN | EPOLLRDNORM; /* readable */
664 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
665 mask |= EPOLLHUP;
666 if (tty_hung_up_p(filp))
667 mask |= EPOLLHUP;
668 if (!tty_is_writelocked(tty) &&
669 !list_empty(&n_hdlc->tx_free_buf_list.list))
670 mask |= EPOLLOUT | EPOLLWRNORM; /* writable */
671
672 return mask;
673} /* end of n_hdlc_tty_poll() */
674
675static void n_hdlc_alloc_buf(struct n_hdlc_buf_list *list, unsigned int count,
676 const char *name)
677{
678 struct n_hdlc_buf *buf;
679 unsigned int i;
680
681 for (i = 0; i < count; i++) {
682 buf = kmalloc(struct_size(buf, buf, maxframe), GFP_KERNEL);
683 if (!buf) {
684 pr_debug("%s(), kmalloc() failed for %s buffer %u\n",
685 __func__, name, i);
686 return;
687 }
688 n_hdlc_buf_put(list, buf);
689 }
690}
691
692/**
693 * n_hdlc_alloc - allocate an n_hdlc instance data structure
694 *
695 * Returns a pointer to newly created structure if success, otherwise %NULL
696 */
697static struct n_hdlc *n_hdlc_alloc(void)
698{
699 struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL);
700
701 if (!n_hdlc)
702 return NULL;
703
704 spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);
705 spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
706 spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
707 spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
708
709 INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);
710 INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);
711 INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);
712 INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);
713
714 n_hdlc_alloc_buf(&n_hdlc->rx_free_buf_list, DEFAULT_RX_BUF_COUNT, "rx");
715 n_hdlc_alloc_buf(&n_hdlc->tx_free_buf_list, DEFAULT_TX_BUF_COUNT, "tx");
716
717 return n_hdlc;
718
719} /* end of n_hdlc_alloc() */
720
721/**
722 * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
723 * @buf_list: pointer to the buffer list
724 * @buf: pointer to the buffer
725 */
726static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
727 struct n_hdlc_buf *buf)
728{
729 unsigned long flags;
730
731 spin_lock_irqsave(&buf_list->spinlock, flags);
732
733 list_add(&buf->list_item, &buf_list->list);
734 buf_list->count++;
735
736 spin_unlock_irqrestore(&buf_list->spinlock, flags);
737}
738
739/**
740 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
741 * @buf_list: pointer to buffer list
742 * @buf: pointer to buffer
743 */
744static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
745 struct n_hdlc_buf *buf)
746{
747 unsigned long flags;
748
749 spin_lock_irqsave(&buf_list->spinlock, flags);
750
751 list_add_tail(&buf->list_item, &buf_list->list);
752 buf_list->count++;
753
754 spin_unlock_irqrestore(&buf_list->spinlock, flags);
755} /* end of n_hdlc_buf_put() */
756
757/**
758 * n_hdlc_buf_get - remove and return an HDLC buffer from list
759 * @buf_list: pointer to HDLC buffer list
760 *
761 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
762 * list.
763 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
764 */
765static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
766{
767 unsigned long flags;
768 struct n_hdlc_buf *buf;
769
770 spin_lock_irqsave(&buf_list->spinlock, flags);
771
772 buf = list_first_entry_or_null(&buf_list->list,
773 struct n_hdlc_buf, list_item);
774 if (buf) {
775 list_del(&buf->list_item);
776 buf_list->count--;
777 }
778
779 spin_unlock_irqrestore(&buf_list->spinlock, flags);
780 return buf;
781} /* end of n_hdlc_buf_get() */
782
783static struct tty_ldisc_ops n_hdlc_ldisc = {
784 .owner = THIS_MODULE,
785 .num = N_HDLC,
786 .name = "hdlc",
787 .open = n_hdlc_tty_open,
788 .close = n_hdlc_tty_close,
789 .read = n_hdlc_tty_read,
790 .write = n_hdlc_tty_write,
791 .ioctl = n_hdlc_tty_ioctl,
792 .poll = n_hdlc_tty_poll,
793 .receive_buf = n_hdlc_tty_receive,
794 .write_wakeup = n_hdlc_tty_wakeup,
795 .flush_buffer = flush_rx_queue,
796};
797
798static int __init n_hdlc_init(void)
799{
800 int status;
801
802 /* range check maxframe arg */
803 maxframe = clamp(maxframe, 4096, MAX_HDLC_FRAME_SIZE);
804
805 status = tty_register_ldisc(&n_hdlc_ldisc);
806 if (!status)
807 pr_info("N_HDLC line discipline registered with maxframe=%d\n",
808 maxframe);
809 else
810 pr_err("N_HDLC: error registering line discipline: %d\n",
811 status);
812
813 return status;
814
815} /* end of init_module() */
816
817static void __exit n_hdlc_exit(void)
818{
819 tty_unregister_ldisc(&n_hdlc_ldisc);
820}
821
822module_init(n_hdlc_init);
823module_exit(n_hdlc_exit);
824
825MODULE_LICENSE("GPL");
826MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
827module_param(maxframe, int, 0);
828MODULE_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/system.h>
106#include <asm/termios.h>
107#include <asm/uaccess.h>
108
109/*
110 * Buffers for individual HDLC frames
111 */
112#define MAX_HDLC_FRAME_SIZE 65535
113#define DEFAULT_RX_BUF_COUNT 10
114#define MAX_RX_BUF_COUNT 60
115#define DEFAULT_TX_BUF_COUNT 3
116
117struct n_hdlc_buf {
118 struct n_hdlc_buf *link;
119 int count;
120 char buf[1];
121};
122
123#define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
124
125struct n_hdlc_buf_list {
126 struct n_hdlc_buf *head;
127 struct n_hdlc_buf *tail;
128 int count;
129 spinlock_t spinlock;
130};
131
132/**
133 * struct n_hdlc - per device instance data structure
134 * @magic - magic value for structure
135 * @flags - miscellaneous control flags
136 * @tty - ptr to TTY structure
137 * @backup_tty - TTY to use if tty gets closed
138 * @tbusy - reentrancy flag for tx wakeup code
139 * @woke_up - FIXME: describe this field
140 * @tbuf - currently transmitting tx buffer
141 * @tx_buf_list - list of pending transmit frame buffers
142 * @rx_buf_list - list of received frame buffers
143 * @tx_free_buf_list - list unused transmit frame buffers
144 * @rx_free_buf_list - list unused received frame buffers
145 */
146struct n_hdlc {
147 int magic;
148 __u32 flags;
149 struct tty_struct *tty;
150 struct tty_struct *backup_tty;
151 int tbusy;
152 int woke_up;
153 struct n_hdlc_buf *tbuf;
154 struct n_hdlc_buf_list tx_buf_list;
155 struct n_hdlc_buf_list rx_buf_list;
156 struct n_hdlc_buf_list tx_free_buf_list;
157 struct n_hdlc_buf_list rx_free_buf_list;
158};
159
160/*
161 * HDLC buffer list manipulation functions
162 */
163static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list);
164static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
165 struct n_hdlc_buf *buf);
166static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
167
168/* Local functions */
169
170static struct n_hdlc *n_hdlc_alloc (void);
171
172/* debug level can be set by insmod for debugging purposes */
173#define DEBUG_LEVEL_INFO 1
174static int debuglevel;
175
176/* max frame size for memory allocations */
177static int maxframe = 4096;
178
179/* TTY callbacks */
180
181static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
182 __u8 __user *buf, size_t nr);
183static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
184 const unsigned char *buf, size_t nr);
185static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
186 unsigned int cmd, unsigned long arg);
187static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
188 poll_table *wait);
189static int n_hdlc_tty_open(struct tty_struct *tty);
190static void n_hdlc_tty_close(struct tty_struct *tty);
191static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
192 char *fp, int count);
193static void n_hdlc_tty_wakeup(struct tty_struct *tty);
194
195#define bset(p,b) ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
196
197#define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
198#define n_hdlc2tty(n_hdlc) ((n_hdlc)->tty)
199
200static void flush_rx_queue(struct tty_struct *tty)
201{
202 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
203 struct n_hdlc_buf *buf;
204
205 while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
206 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
207}
208
209static void flush_tx_queue(struct tty_struct *tty)
210{
211 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
212 struct n_hdlc_buf *buf;
213 unsigned long flags;
214
215 while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
216 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
217 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
218 if (n_hdlc->tbuf) {
219 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, n_hdlc->tbuf);
220 n_hdlc->tbuf = NULL;
221 }
222 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
223}
224
225static struct tty_ldisc_ops n_hdlc_ldisc = {
226 .owner = THIS_MODULE,
227 .magic = TTY_LDISC_MAGIC,
228 .name = "hdlc",
229 .open = n_hdlc_tty_open,
230 .close = n_hdlc_tty_close,
231 .read = n_hdlc_tty_read,
232 .write = n_hdlc_tty_write,
233 .ioctl = n_hdlc_tty_ioctl,
234 .poll = n_hdlc_tty_poll,
235 .receive_buf = n_hdlc_tty_receive,
236 .write_wakeup = n_hdlc_tty_wakeup,
237 .flush_buffer = flush_rx_queue,
238};
239
240/**
241 * n_hdlc_release - release an n_hdlc per device line discipline info structure
242 * @n_hdlc - per device line discipline info structure
243 */
244static void n_hdlc_release(struct n_hdlc *n_hdlc)
245{
246 struct tty_struct *tty = n_hdlc2tty (n_hdlc);
247 struct n_hdlc_buf *buf;
248
249 if (debuglevel >= DEBUG_LEVEL_INFO)
250 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
251
252 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
253 wake_up_interruptible (&tty->read_wait);
254 wake_up_interruptible (&tty->write_wait);
255
256 if (tty->disc_data == n_hdlc)
257 tty->disc_data = NULL; /* Break the tty->n_hdlc link */
258
259 /* Release transmit and receive buffers */
260 for(;;) {
261 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
262 if (buf) {
263 kfree(buf);
264 } else
265 break;
266 }
267 for(;;) {
268 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
269 if (buf) {
270 kfree(buf);
271 } else
272 break;
273 }
274 for(;;) {
275 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
276 if (buf) {
277 kfree(buf);
278 } else
279 break;
280 }
281 for(;;) {
282 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
283 if (buf) {
284 kfree(buf);
285 } else
286 break;
287 }
288 kfree(n_hdlc->tbuf);
289 kfree(n_hdlc);
290
291} /* end of n_hdlc_release() */
292
293/**
294 * n_hdlc_tty_close - line discipline close
295 * @tty - pointer to tty info structure
296 *
297 * Called when the line discipline is changed to something
298 * else, the tty is closed, or the tty detects a hangup.
299 */
300static void n_hdlc_tty_close(struct tty_struct *tty)
301{
302 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
303
304 if (debuglevel >= DEBUG_LEVEL_INFO)
305 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
306
307 if (n_hdlc != NULL) {
308 if (n_hdlc->magic != HDLC_MAGIC) {
309 printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
310 return;
311 }
312#if defined(TTY_NO_WRITE_SPLIT)
313 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
314#endif
315 tty->disc_data = NULL;
316 if (tty == n_hdlc->backup_tty)
317 n_hdlc->backup_tty = NULL;
318 if (tty != n_hdlc->tty)
319 return;
320 if (n_hdlc->backup_tty) {
321 n_hdlc->tty = n_hdlc->backup_tty;
322 } else {
323 n_hdlc_release (n_hdlc);
324 }
325 }
326
327 if (debuglevel >= DEBUG_LEVEL_INFO)
328 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
329
330} /* end of n_hdlc_tty_close() */
331
332/**
333 * n_hdlc_tty_open - called when line discipline changed to n_hdlc
334 * @tty - pointer to tty info structure
335 *
336 * Returns 0 if success, otherwise error code
337 */
338static int n_hdlc_tty_open (struct tty_struct *tty)
339{
340 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
341
342 if (debuglevel >= DEBUG_LEVEL_INFO)
343 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
344 __FILE__,__LINE__,
345 tty->name);
346
347 /* There should not be an existing table for this slot. */
348 if (n_hdlc) {
349 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
350 return -EEXIST;
351 }
352
353 n_hdlc = n_hdlc_alloc();
354 if (!n_hdlc) {
355 printk (KERN_ERR "n_hdlc_alloc failed\n");
356 return -ENFILE;
357 }
358
359 tty->disc_data = n_hdlc;
360 n_hdlc->tty = tty;
361 tty->receive_room = 65536;
362
363#if defined(TTY_NO_WRITE_SPLIT)
364 /* change tty_io write() to not split large writes into 8K chunks */
365 set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
366#endif
367
368 /* flush receive data from driver */
369 tty_driver_flush_buffer(tty);
370
371 if (debuglevel >= DEBUG_LEVEL_INFO)
372 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
373
374 return 0;
375
376} /* end of n_tty_hdlc_open() */
377
378/**
379 * n_hdlc_send_frames - send frames on pending send buffer list
380 * @n_hdlc - pointer to ldisc instance data
381 * @tty - pointer to tty instance data
382 *
383 * Send frames on pending send buffer list until the driver does not accept a
384 * frame (busy) this function is called after adding a frame to the send buffer
385 * list and by the tty wakeup callback.
386 */
387static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
388{
389 register int actual;
390 unsigned long flags;
391 struct n_hdlc_buf *tbuf;
392
393 if (debuglevel >= DEBUG_LEVEL_INFO)
394 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
395 check_again:
396
397 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
398 if (n_hdlc->tbusy) {
399 n_hdlc->woke_up = 1;
400 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
401 return;
402 }
403 n_hdlc->tbusy = 1;
404 n_hdlc->woke_up = 0;
405 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
406
407 /* get current transmit buffer or get new transmit */
408 /* buffer from list of pending transmit buffers */
409
410 tbuf = n_hdlc->tbuf;
411 if (!tbuf)
412 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
413
414 while (tbuf) {
415 if (debuglevel >= DEBUG_LEVEL_INFO)
416 printk("%s(%d)sending frame %p, count=%d\n",
417 __FILE__,__LINE__,tbuf,tbuf->count);
418
419 /* Send the next block of data to device */
420 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
421 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
422
423 /* rollback was possible and has been done */
424 if (actual == -ERESTARTSYS) {
425 n_hdlc->tbuf = tbuf;
426 break;
427 }
428 /* if transmit error, throw frame away by */
429 /* pretending it was accepted by driver */
430 if (actual < 0)
431 actual = tbuf->count;
432
433 if (actual == tbuf->count) {
434 if (debuglevel >= DEBUG_LEVEL_INFO)
435 printk("%s(%d)frame %p completed\n",
436 __FILE__,__LINE__,tbuf);
437
438 /* free current transmit buffer */
439 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
440
441 /* this tx buffer is done */
442 n_hdlc->tbuf = NULL;
443
444 /* wait up sleeping writers */
445 wake_up_interruptible(&tty->write_wait);
446
447 /* get next pending transmit buffer */
448 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
449 } else {
450 if (debuglevel >= DEBUG_LEVEL_INFO)
451 printk("%s(%d)frame %p pending\n",
452 __FILE__,__LINE__,tbuf);
453
454 /* buffer not accepted by driver */
455 /* set this buffer as pending buffer */
456 n_hdlc->tbuf = tbuf;
457 break;
458 }
459 }
460
461 if (!tbuf)
462 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
463
464 /* Clear the re-entry flag */
465 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
466 n_hdlc->tbusy = 0;
467 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
468
469 if (n_hdlc->woke_up)
470 goto check_again;
471
472 if (debuglevel >= DEBUG_LEVEL_INFO)
473 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
474
475} /* end of n_hdlc_send_frames() */
476
477/**
478 * n_hdlc_tty_wakeup - Callback for transmit wakeup
479 * @tty - pointer to associated tty instance data
480 *
481 * Called when low level device driver can accept more send data.
482 */
483static void n_hdlc_tty_wakeup(struct tty_struct *tty)
484{
485 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
486
487 if (debuglevel >= DEBUG_LEVEL_INFO)
488 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
489
490 if (!n_hdlc)
491 return;
492
493 if (tty != n_hdlc->tty) {
494 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
495 return;
496 }
497
498 n_hdlc_send_frames (n_hdlc, tty);
499
500} /* end of n_hdlc_tty_wakeup() */
501
502/**
503 * n_hdlc_tty_receive - Called by tty driver when receive data is available
504 * @tty - pointer to tty instance data
505 * @data - pointer to received data
506 * @flags - pointer to flags for data
507 * @count - count of received data in bytes
508 *
509 * Called by tty low level driver when receive data is available. Data is
510 * interpreted as one HDLC frame.
511 */
512static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
513 char *flags, int count)
514{
515 register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
516 register struct n_hdlc_buf *buf;
517
518 if (debuglevel >= DEBUG_LEVEL_INFO)
519 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
520 __FILE__,__LINE__, count);
521
522 /* This can happen if stuff comes in on the backup tty */
523 if (!n_hdlc || tty != n_hdlc->tty)
524 return;
525
526 /* verify line is using HDLC discipline */
527 if (n_hdlc->magic != HDLC_MAGIC) {
528 printk("%s(%d) line not using HDLC discipline\n",
529 __FILE__,__LINE__);
530 return;
531 }
532
533 if ( count>maxframe ) {
534 if (debuglevel >= DEBUG_LEVEL_INFO)
535 printk("%s(%d) rx count>maxframesize, data discarded\n",
536 __FILE__,__LINE__);
537 return;
538 }
539
540 /* get a free HDLC buffer */
541 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
542 if (!buf) {
543 /* no buffers in free list, attempt to allocate another rx buffer */
544 /* unless the maximum count has been reached */
545 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
546 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
547 }
548
549 if (!buf) {
550 if (debuglevel >= DEBUG_LEVEL_INFO)
551 printk("%s(%d) no more rx buffers, data discarded\n",
552 __FILE__,__LINE__);
553 return;
554 }
555
556 /* copy received data to HDLC buffer */
557 memcpy(buf->buf,data,count);
558 buf->count=count;
559
560 /* add HDLC buffer to list of received frames */
561 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
562
563 /* wake up any blocked reads and perform async signalling */
564 wake_up_interruptible (&tty->read_wait);
565 if (n_hdlc->tty->fasync != NULL)
566 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
567
568} /* end of n_hdlc_tty_receive() */
569
570/**
571 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
572 * @tty - pointer to tty instance data
573 * @file - pointer to open file object
574 * @buf - pointer to returned data buffer
575 * @nr - size of returned data buffer
576 *
577 * Returns the number of bytes returned or error code.
578 */
579static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
580 __u8 __user *buf, size_t nr)
581{
582 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
583 int ret = 0;
584 struct n_hdlc_buf *rbuf;
585 DECLARE_WAITQUEUE(wait, current);
586
587 if (debuglevel >= DEBUG_LEVEL_INFO)
588 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
589
590 /* Validate the pointers */
591 if (!n_hdlc)
592 return -EIO;
593
594 /* verify user access to buffer */
595 if (!access_ok(VERIFY_WRITE, buf, nr)) {
596 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
597 "buffer\n", __FILE__, __LINE__);
598 return -EFAULT;
599 }
600
601 add_wait_queue(&tty->read_wait, &wait);
602
603 for (;;) {
604 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
605 ret = -EIO;
606 break;
607 }
608 if (tty_hung_up_p(file))
609 break;
610
611 set_current_state(TASK_INTERRUPTIBLE);
612
613 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
614 if (rbuf) {
615 if (rbuf->count > nr) {
616 /* too large for caller's buffer */
617 ret = -EOVERFLOW;
618 } else {
619 if (copy_to_user(buf, rbuf->buf, rbuf->count))
620 ret = -EFAULT;
621 else
622 ret = rbuf->count;
623 }
624
625 if (n_hdlc->rx_free_buf_list.count >
626 DEFAULT_RX_BUF_COUNT)
627 kfree(rbuf);
628 else
629 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
630 break;
631 }
632
633 /* no data */
634 if (file->f_flags & O_NONBLOCK) {
635 ret = -EAGAIN;
636 break;
637 }
638
639 schedule();
640
641 if (signal_pending(current)) {
642 ret = -EINTR;
643 break;
644 }
645 }
646
647 remove_wait_queue(&tty->read_wait, &wait);
648 __set_current_state(TASK_RUNNING);
649
650 return ret;
651
652} /* end of n_hdlc_tty_read() */
653
654/**
655 * n_hdlc_tty_write - write a single frame of data to device
656 * @tty - pointer to associated tty device instance data
657 * @file - pointer to file object data
658 * @data - pointer to transmit data (one frame)
659 * @count - size of transmit frame in bytes
660 *
661 * Returns the number of bytes written (or error code).
662 */
663static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
664 const unsigned char *data, size_t count)
665{
666 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
667 int error = 0;
668 DECLARE_WAITQUEUE(wait, current);
669 struct n_hdlc_buf *tbuf;
670
671 if (debuglevel >= DEBUG_LEVEL_INFO)
672 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
673 __FILE__,__LINE__,count);
674
675 /* Verify pointers */
676 if (!n_hdlc)
677 return -EIO;
678
679 if (n_hdlc->magic != HDLC_MAGIC)
680 return -EIO;
681
682 /* verify frame size */
683 if (count > maxframe ) {
684 if (debuglevel & DEBUG_LEVEL_INFO)
685 printk (KERN_WARNING
686 "n_hdlc_tty_write: truncating user packet "
687 "from %lu to %d\n", (unsigned long) count,
688 maxframe );
689 count = maxframe;
690 }
691
692 add_wait_queue(&tty->write_wait, &wait);
693
694 for (;;) {
695 set_current_state(TASK_INTERRUPTIBLE);
696
697 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
698 if (tbuf)
699 break;
700
701 if (file->f_flags & O_NONBLOCK) {
702 error = -EAGAIN;
703 break;
704 }
705 schedule();
706
707 n_hdlc = tty2n_hdlc (tty);
708 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
709 tty != n_hdlc->tty) {
710 printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
711 error = -EIO;
712 break;
713 }
714
715 if (signal_pending(current)) {
716 error = -EINTR;
717 break;
718 }
719 }
720
721 __set_current_state(TASK_RUNNING);
722 remove_wait_queue(&tty->write_wait, &wait);
723
724 if (!error) {
725 /* Retrieve the user's buffer */
726 memcpy(tbuf->buf, data, count);
727
728 /* Send the data */
729 tbuf->count = error = count;
730 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
731 n_hdlc_send_frames(n_hdlc,tty);
732 }
733
734 return error;
735
736} /* end of n_hdlc_tty_write() */
737
738/**
739 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
740 * @tty - pointer to tty instance data
741 * @file - pointer to open file object for device
742 * @cmd - IOCTL command code
743 * @arg - argument for IOCTL call (cmd dependent)
744 *
745 * Returns command dependent result.
746 */
747static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
748 unsigned int cmd, unsigned long arg)
749{
750 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
751 int error = 0;
752 int count;
753 unsigned long flags;
754
755 if (debuglevel >= DEBUG_LEVEL_INFO)
756 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
757 __FILE__,__LINE__,cmd);
758
759 /* Verify the status of the device */
760 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
761 return -EBADF;
762
763 switch (cmd) {
764 case FIONREAD:
765 /* report count of read data available */
766 /* in next available frame (if any) */
767 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
768 if (n_hdlc->rx_buf_list.head)
769 count = n_hdlc->rx_buf_list.head->count;
770 else
771 count = 0;
772 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
773 error = put_user(count, (int __user *)arg);
774 break;
775
776 case TIOCOUTQ:
777 /* get the pending tx byte count in the driver */
778 count = tty_chars_in_buffer(tty);
779 /* add size of next output frame in queue */
780 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
781 if (n_hdlc->tx_buf_list.head)
782 count += n_hdlc->tx_buf_list.head->count;
783 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
784 error = put_user(count, (int __user *)arg);
785 break;
786
787 case TCFLSH:
788 switch (arg) {
789 case TCIOFLUSH:
790 case TCOFLUSH:
791 flush_tx_queue(tty);
792 }
793 /* fall through to default */
794
795 default:
796 error = n_tty_ioctl_helper(tty, file, cmd, arg);
797 break;
798 }
799 return error;
800
801} /* end of n_hdlc_tty_ioctl() */
802
803/**
804 * n_hdlc_tty_poll - TTY callback for poll system call
805 * @tty - pointer to tty instance data
806 * @filp - pointer to open file object for device
807 * @poll_table - wait queue for operations
808 *
809 * Determine which operations (read/write) will not block and return info
810 * to caller.
811 * Returns a bit mask containing info on which ops will not block.
812 */
813static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
814 poll_table *wait)
815{
816 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
817 unsigned int mask = 0;
818
819 if (debuglevel >= DEBUG_LEVEL_INFO)
820 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
821
822 if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
823 /* queue current process into any wait queue that */
824 /* may awaken in the future (read and write) */
825
826 poll_wait(filp, &tty->read_wait, wait);
827 poll_wait(filp, &tty->write_wait, wait);
828
829 /* set bits for operations that won't block */
830 if (n_hdlc->rx_buf_list.head)
831 mask |= POLLIN | POLLRDNORM; /* readable */
832 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
833 mask |= POLLHUP;
834 if (tty_hung_up_p(filp))
835 mask |= POLLHUP;
836 if (!tty_is_writelocked(tty) &&
837 n_hdlc->tx_free_buf_list.head)
838 mask |= POLLOUT | POLLWRNORM; /* writable */
839 }
840 return mask;
841} /* end of n_hdlc_tty_poll() */
842
843/**
844 * n_hdlc_alloc - allocate an n_hdlc instance data structure
845 *
846 * Returns a pointer to newly created structure if success, otherwise %NULL
847 */
848static struct n_hdlc *n_hdlc_alloc(void)
849{
850 struct n_hdlc_buf *buf;
851 int i;
852 struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
853
854 if (!n_hdlc)
855 return NULL;
856
857 memset(n_hdlc, 0, sizeof(*n_hdlc));
858
859 n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
860 n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
861 n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
862 n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
863
864 /* allocate free rx buffer list */
865 for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
866 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
867 if (buf)
868 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
869 else if (debuglevel >= DEBUG_LEVEL_INFO)
870 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
871 }
872
873 /* allocate free tx buffer list */
874 for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
875 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
876 if (buf)
877 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
878 else if (debuglevel >= DEBUG_LEVEL_INFO)
879 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
880 }
881
882 /* Initialize the control block */
883 n_hdlc->magic = HDLC_MAGIC;
884 n_hdlc->flags = 0;
885
886 return n_hdlc;
887
888} /* end of n_hdlc_alloc() */
889
890/**
891 * n_hdlc_buf_list_init - initialize specified HDLC buffer list
892 * @list - pointer to buffer list
893 */
894static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
895{
896 memset(list, 0, sizeof(*list));
897 spin_lock_init(&list->spinlock);
898} /* end of n_hdlc_buf_list_init() */
899
900/**
901 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
902 * @list - pointer to buffer list
903 * @buf - pointer to buffer
904 */
905static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
906 struct n_hdlc_buf *buf)
907{
908 unsigned long flags;
909 spin_lock_irqsave(&list->spinlock,flags);
910
911 buf->link=NULL;
912 if (list->tail)
913 list->tail->link = buf;
914 else
915 list->head = buf;
916 list->tail = buf;
917 (list->count)++;
918
919 spin_unlock_irqrestore(&list->spinlock,flags);
920
921} /* end of n_hdlc_buf_put() */
922
923/**
924 * n_hdlc_buf_get - remove and return an HDLC buffer from list
925 * @list - pointer to HDLC buffer list
926 *
927 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
928 * list.
929 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
930 */
931static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
932{
933 unsigned long flags;
934 struct n_hdlc_buf *buf;
935 spin_lock_irqsave(&list->spinlock,flags);
936
937 buf = list->head;
938 if (buf) {
939 list->head = buf->link;
940 (list->count)--;
941 }
942 if (!list->head)
943 list->tail = NULL;
944
945 spin_unlock_irqrestore(&list->spinlock,flags);
946 return buf;
947
948} /* end of n_hdlc_buf_get() */
949
950static char hdlc_banner[] __initdata =
951 KERN_INFO "HDLC line discipline maxframe=%u\n";
952static char hdlc_register_ok[] __initdata =
953 KERN_INFO "N_HDLC line discipline registered.\n";
954static char hdlc_register_fail[] __initdata =
955 KERN_ERR "error registering line discipline: %d\n";
956static char hdlc_init_fail[] __initdata =
957 KERN_INFO "N_HDLC: init failure %d\n";
958
959static int __init n_hdlc_init(void)
960{
961 int status;
962
963 /* range check maxframe arg */
964 if (maxframe < 4096)
965 maxframe = 4096;
966 else if (maxframe > 65535)
967 maxframe = 65535;
968
969 printk(hdlc_banner, maxframe);
970
971 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
972 if (!status)
973 printk(hdlc_register_ok);
974 else
975 printk(hdlc_register_fail, status);
976
977 if (status)
978 printk(hdlc_init_fail, status);
979 return status;
980
981} /* end of init_module() */
982
983static char hdlc_unregister_ok[] __exitdata =
984 KERN_INFO "N_HDLC: line discipline unregistered\n";
985static char hdlc_unregister_fail[] __exitdata =
986 KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
987
988static void __exit n_hdlc_exit(void)
989{
990 /* Release tty registration of line discipline */
991 int status = tty_unregister_ldisc(N_HDLC);
992
993 if (status)
994 printk(hdlc_unregister_fail, status);
995 else
996 printk(hdlc_unregister_ok);
997}
998
999module_init(n_hdlc_init);
1000module_exit(n_hdlc_exit);
1001
1002MODULE_LICENSE("GPL");
1003MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
1004module_param(debuglevel, int, 0);
1005module_param(maxframe, int, 0);
1006MODULE_ALIAS_LDISC(N_HDLC);