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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#include "tty.h"
104
105/*
106 * Buffers for individual HDLC frames
107 */
108#define MAX_HDLC_FRAME_SIZE 65535
109#define DEFAULT_RX_BUF_COUNT 10
110#define MAX_RX_BUF_COUNT 60
111#define DEFAULT_TX_BUF_COUNT 3
112
113struct n_hdlc_buf {
114 struct list_head list_item;
115 int count;
116 char buf[];
117};
118
119struct n_hdlc_buf_list {
120 struct list_head list;
121 int count;
122 spinlock_t spinlock;
123};
124
125/**
126 * struct n_hdlc - per device instance data structure
127 * @magic: magic value for structure
128 * @tbusy: reentrancy flag for tx wakeup code
129 * @woke_up: tx wakeup needs to be run again as it was called while @tbusy
130 * @tx_buf_list: list of pending transmit frame buffers
131 * @rx_buf_list: list of received frame buffers
132 * @tx_free_buf_list: list unused transmit frame buffers
133 * @rx_free_buf_list: list unused received frame buffers
134 */
135struct n_hdlc {
136 int magic;
137 bool tbusy;
138 bool woke_up;
139 struct n_hdlc_buf_list tx_buf_list;
140 struct n_hdlc_buf_list rx_buf_list;
141 struct n_hdlc_buf_list tx_free_buf_list;
142 struct n_hdlc_buf_list rx_free_buf_list;
143};
144
145/*
146 * HDLC buffer list manipulation functions
147 */
148static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
149 struct n_hdlc_buf *buf);
150static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
151 struct n_hdlc_buf *buf);
152static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
153
154/* Local functions */
155
156static struct n_hdlc *n_hdlc_alloc(void);
157
158/* max frame size for memory allocations */
159static int maxframe = 4096;
160
161static void flush_rx_queue(struct tty_struct *tty)
162{
163 struct n_hdlc *n_hdlc = tty->disc_data;
164 struct n_hdlc_buf *buf;
165
166 while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
167 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
168}
169
170static void flush_tx_queue(struct tty_struct *tty)
171{
172 struct n_hdlc *n_hdlc = tty->disc_data;
173 struct n_hdlc_buf *buf;
174
175 while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
176 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
177}
178
179static void n_hdlc_free_buf_list(struct n_hdlc_buf_list *list)
180{
181 struct n_hdlc_buf *buf;
182
183 do {
184 buf = n_hdlc_buf_get(list);
185 kfree(buf);
186 } while (buf);
187}
188
189/**
190 * n_hdlc_tty_close - line discipline close
191 * @tty: pointer to tty info structure
192 *
193 * Called when the line discipline is changed to something
194 * else, the tty is closed, or the tty detects a hangup.
195 */
196static void n_hdlc_tty_close(struct tty_struct *tty)
197{
198 struct n_hdlc *n_hdlc = tty->disc_data;
199
200 if (n_hdlc->magic != HDLC_MAGIC) {
201 pr_warn("n_hdlc: trying to close unopened tty!\n");
202 return;
203 }
204#if defined(TTY_NO_WRITE_SPLIT)
205 clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags);
206#endif
207 tty->disc_data = NULL;
208
209 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
210 wake_up_interruptible(&tty->read_wait);
211 wake_up_interruptible(&tty->write_wait);
212
213 n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list);
214 n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list);
215 n_hdlc_free_buf_list(&n_hdlc->rx_buf_list);
216 n_hdlc_free_buf_list(&n_hdlc->tx_buf_list);
217 kfree(n_hdlc);
218} /* end of n_hdlc_tty_close() */
219
220/**
221 * n_hdlc_tty_open - called when line discipline changed to n_hdlc
222 * @tty: pointer to tty info structure
223 *
224 * Returns 0 if success, otherwise error code
225 */
226static int n_hdlc_tty_open(struct tty_struct *tty)
227{
228 struct n_hdlc *n_hdlc = tty->disc_data;
229
230 pr_debug("%s() called (device=%s)\n", __func__, tty->name);
231
232 /* There should not be an existing table for this slot. */
233 if (n_hdlc) {
234 pr_err("%s: tty already associated!\n", __func__);
235 return -EEXIST;
236 }
237
238 n_hdlc = n_hdlc_alloc();
239 if (!n_hdlc) {
240 pr_err("%s: n_hdlc_alloc failed\n", __func__);
241 return -ENFILE;
242 }
243
244 tty->disc_data = n_hdlc;
245 tty->receive_room = 65536;
246
247 /* change tty_io write() to not split large writes into 8K chunks */
248 set_bit(TTY_NO_WRITE_SPLIT, &tty->flags);
249
250 /* flush receive data from driver */
251 tty_driver_flush_buffer(tty);
252
253 return 0;
254
255} /* end of n_tty_hdlc_open() */
256
257/**
258 * n_hdlc_send_frames - send frames on pending send buffer list
259 * @n_hdlc: pointer to ldisc instance data
260 * @tty: pointer to tty instance data
261 *
262 * Send frames on pending send buffer list until the driver does not accept a
263 * frame (busy) this function is called after adding a frame to the send buffer
264 * list and by the tty wakeup callback.
265 */
266static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
267{
268 register int actual;
269 unsigned long flags;
270 struct n_hdlc_buf *tbuf;
271
272check_again:
273
274 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
275 if (n_hdlc->tbusy) {
276 n_hdlc->woke_up = true;
277 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
278 return;
279 }
280 n_hdlc->tbusy = true;
281 n_hdlc->woke_up = false;
282 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
283
284 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
285 while (tbuf) {
286 pr_debug("sending frame %p, count=%d\n", tbuf, tbuf->count);
287
288 /* Send the next block of data to device */
289 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
290 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
291
292 /* rollback was possible and has been done */
293 if (actual == -ERESTARTSYS) {
294 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
295 break;
296 }
297 /* if transmit error, throw frame away by */
298 /* pretending it was accepted by driver */
299 if (actual < 0)
300 actual = tbuf->count;
301
302 if (actual == tbuf->count) {
303 pr_debug("frame %p completed\n", tbuf);
304
305 /* free current transmit buffer */
306 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
307
308 /* wait up sleeping writers */
309 wake_up_interruptible(&tty->write_wait);
310
311 /* get next pending transmit buffer */
312 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
313 } else {
314 pr_debug("frame %p pending\n", tbuf);
315
316 /*
317 * the buffer was not accepted by driver,
318 * return it back into tx queue
319 */
320 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
321 break;
322 }
323 }
324
325 if (!tbuf)
326 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
327
328 /* Clear the re-entry flag */
329 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
330 n_hdlc->tbusy = false;
331 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
332
333 if (n_hdlc->woke_up)
334 goto check_again;
335} /* end of n_hdlc_send_frames() */
336
337/**
338 * n_hdlc_tty_wakeup - Callback for transmit wakeup
339 * @tty: pointer to associated tty instance data
340 *
341 * Called when low level device driver can accept more send data.
342 */
343static void n_hdlc_tty_wakeup(struct tty_struct *tty)
344{
345 struct n_hdlc *n_hdlc = tty->disc_data;
346
347 n_hdlc_send_frames(n_hdlc, tty);
348} /* end of n_hdlc_tty_wakeup() */
349
350/**
351 * n_hdlc_tty_receive - Called by tty driver when receive data is available
352 * @tty: pointer to tty instance data
353 * @data: pointer to received data
354 * @flags: pointer to flags for data
355 * @count: count of received data in bytes
356 *
357 * Called by tty low level driver when receive data is available. Data is
358 * interpreted as one HDLC frame.
359 */
360static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
361 const char *flags, int count)
362{
363 register struct n_hdlc *n_hdlc = tty->disc_data;
364 register struct n_hdlc_buf *buf;
365
366 pr_debug("%s() called count=%d\n", __func__, count);
367
368 /* verify line is using HDLC discipline */
369 if (n_hdlc->magic != HDLC_MAGIC) {
370 pr_err("line not using HDLC discipline\n");
371 return;
372 }
373
374 if (count > maxframe) {
375 pr_debug("rx count>maxframesize, data discarded\n");
376 return;
377 }
378
379 /* get a free HDLC buffer */
380 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
381 if (!buf) {
382 /*
383 * no buffers in free list, attempt to allocate another rx
384 * buffer unless the maximum count has been reached
385 */
386 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
387 buf = kmalloc(struct_size(buf, buf, maxframe),
388 GFP_ATOMIC);
389 }
390
391 if (!buf) {
392 pr_debug("no more rx buffers, data discarded\n");
393 return;
394 }
395
396 /* copy received data to HDLC buffer */
397 memcpy(buf->buf, data, count);
398 buf->count = count;
399
400 /* add HDLC buffer to list of received frames */
401 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
402
403 /* wake up any blocked reads and perform async signalling */
404 wake_up_interruptible(&tty->read_wait);
405 if (tty->fasync != NULL)
406 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
407
408} /* end of n_hdlc_tty_receive() */
409
410/**
411 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
412 * @tty: pointer to tty instance data
413 * @file: pointer to open file object
414 * @kbuf: pointer to returned data buffer
415 * @nr: size of returned data buffer
416 * @cookie: stored rbuf from previous run
417 * @offset: offset into the data buffer
418 *
419 * Returns the number of bytes returned or error code.
420 */
421static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
422 __u8 *kbuf, size_t nr,
423 void **cookie, unsigned long offset)
424{
425 struct n_hdlc *n_hdlc = tty->disc_data;
426 int ret = 0;
427 struct n_hdlc_buf *rbuf;
428 DECLARE_WAITQUEUE(wait, current);
429
430 /* Is this a repeated call for an rbuf we already found earlier? */
431 rbuf = *cookie;
432 if (rbuf)
433 goto have_rbuf;
434
435 add_wait_queue(&tty->read_wait, &wait);
436
437 for (;;) {
438 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
439 ret = -EIO;
440 break;
441 }
442 if (tty_hung_up_p(file))
443 break;
444
445 set_current_state(TASK_INTERRUPTIBLE);
446
447 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
448 if (rbuf)
449 break;
450
451 /* no data */
452 if (tty_io_nonblock(tty, file)) {
453 ret = -EAGAIN;
454 break;
455 }
456
457 schedule();
458
459 if (signal_pending(current)) {
460 ret = -EINTR;
461 break;
462 }
463 }
464
465 remove_wait_queue(&tty->read_wait, &wait);
466 __set_current_state(TASK_RUNNING);
467
468 if (!rbuf)
469 return ret;
470 *cookie = rbuf;
471
472have_rbuf:
473 /* Have we used it up entirely? */
474 if (offset >= rbuf->count)
475 goto done_with_rbuf;
476
477 /* More data to go, but can't copy any more? EOVERFLOW */
478 ret = -EOVERFLOW;
479 if (!nr)
480 goto done_with_rbuf;
481
482 /* Copy as much data as possible */
483 ret = rbuf->count - offset;
484 if (ret > nr)
485 ret = nr;
486 memcpy(kbuf, rbuf->buf+offset, ret);
487 offset += ret;
488
489 /* If we still have data left, we leave the rbuf in the cookie */
490 if (offset < rbuf->count)
491 return ret;
492
493done_with_rbuf:
494 *cookie = NULL;
495
496 if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
497 kfree(rbuf);
498 else
499 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
500
501 return ret;
502
503} /* end of n_hdlc_tty_read() */
504
505/**
506 * n_hdlc_tty_write - write a single frame of data to device
507 * @tty: pointer to associated tty device instance data
508 * @file: pointer to file object data
509 * @data: pointer to transmit data (one frame)
510 * @count: size of transmit frame in bytes
511 *
512 * Returns the number of bytes written (or error code).
513 */
514static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
515 const unsigned char *data, size_t count)
516{
517 struct n_hdlc *n_hdlc = tty->disc_data;
518 int error = 0;
519 DECLARE_WAITQUEUE(wait, current);
520 struct n_hdlc_buf *tbuf;
521
522 pr_debug("%s() called count=%zd\n", __func__, count);
523
524 if (n_hdlc->magic != HDLC_MAGIC)
525 return -EIO;
526
527 /* verify frame size */
528 if (count > maxframe) {
529 pr_debug("%s: truncating user packet from %zu to %d\n",
530 __func__, count, maxframe);
531 count = maxframe;
532 }
533
534 add_wait_queue(&tty->write_wait, &wait);
535
536 for (;;) {
537 set_current_state(TASK_INTERRUPTIBLE);
538
539 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
540 if (tbuf)
541 break;
542
543 if (tty_io_nonblock(tty, file)) {
544 error = -EAGAIN;
545 break;
546 }
547 schedule();
548
549 if (signal_pending(current)) {
550 error = -EINTR;
551 break;
552 }
553 }
554
555 __set_current_state(TASK_RUNNING);
556 remove_wait_queue(&tty->write_wait, &wait);
557
558 if (!error) {
559 /* Retrieve the user's buffer */
560 memcpy(tbuf->buf, data, count);
561
562 /* Send the data */
563 tbuf->count = error = count;
564 n_hdlc_buf_put(&n_hdlc->tx_buf_list, tbuf);
565 n_hdlc_send_frames(n_hdlc, tty);
566 }
567
568 return error;
569
570} /* end of n_hdlc_tty_write() */
571
572/**
573 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
574 * @tty: pointer to tty instance data
575 * @file: pointer to open file object for device
576 * @cmd: IOCTL command code
577 * @arg: argument for IOCTL call (cmd dependent)
578 *
579 * Returns command dependent result.
580 */
581static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
582 unsigned int cmd, unsigned long arg)
583{
584 struct n_hdlc *n_hdlc = tty->disc_data;
585 int error = 0;
586 int count;
587 unsigned long flags;
588 struct n_hdlc_buf *buf = NULL;
589
590 pr_debug("%s() called %d\n", __func__, cmd);
591
592 /* Verify the status of the device */
593 if (n_hdlc->magic != HDLC_MAGIC)
594 return -EBADF;
595
596 switch (cmd) {
597 case FIONREAD:
598 /* report count of read data available */
599 /* in next available frame (if any) */
600 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags);
601 buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
602 struct n_hdlc_buf, list_item);
603 if (buf)
604 count = buf->count;
605 else
606 count = 0;
607 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags);
608 error = put_user(count, (int __user *)arg);
609 break;
610
611 case TIOCOUTQ:
612 /* get the pending tx byte count in the driver */
613 count = tty_chars_in_buffer(tty);
614 /* add size of next output frame in queue */
615 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
616 buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
617 struct n_hdlc_buf, list_item);
618 if (buf)
619 count += buf->count;
620 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
621 error = put_user(count, (int __user *)arg);
622 break;
623
624 case TCFLSH:
625 switch (arg) {
626 case TCIOFLUSH:
627 case TCOFLUSH:
628 flush_tx_queue(tty);
629 }
630 fallthrough; /* to default */
631
632 default:
633 error = n_tty_ioctl_helper(tty, file, cmd, arg);
634 break;
635 }
636 return error;
637
638} /* end of n_hdlc_tty_ioctl() */
639
640/**
641 * n_hdlc_tty_poll - TTY callback for poll system call
642 * @tty: pointer to tty instance data
643 * @filp: pointer to open file object for device
644 * @wait: wait queue for operations
645 *
646 * Determine which operations (read/write) will not block and return info
647 * to caller.
648 * Returns a bit mask containing info on which ops will not block.
649 */
650static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
651 poll_table *wait)
652{
653 struct n_hdlc *n_hdlc = tty->disc_data;
654 __poll_t mask = 0;
655
656 if (n_hdlc->magic != HDLC_MAGIC)
657 return 0;
658
659 /*
660 * queue the current process into any wait queue that may awaken in the
661 * future (read and write)
662 */
663 poll_wait(filp, &tty->read_wait, wait);
664 poll_wait(filp, &tty->write_wait, wait);
665
666 /* set bits for operations that won't block */
667 if (!list_empty(&n_hdlc->rx_buf_list.list))
668 mask |= EPOLLIN | EPOLLRDNORM; /* readable */
669 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
670 mask |= EPOLLHUP;
671 if (tty_hung_up_p(filp))
672 mask |= EPOLLHUP;
673 if (!tty_is_writelocked(tty) &&
674 !list_empty(&n_hdlc->tx_free_buf_list.list))
675 mask |= EPOLLOUT | EPOLLWRNORM; /* writable */
676
677 return mask;
678} /* end of n_hdlc_tty_poll() */
679
680static void n_hdlc_alloc_buf(struct n_hdlc_buf_list *list, unsigned int count,
681 const char *name)
682{
683 struct n_hdlc_buf *buf;
684 unsigned int i;
685
686 for (i = 0; i < count; i++) {
687 buf = kmalloc(struct_size(buf, buf, maxframe), GFP_KERNEL);
688 if (!buf) {
689 pr_debug("%s(), kmalloc() failed for %s buffer %u\n",
690 __func__, name, i);
691 return;
692 }
693 n_hdlc_buf_put(list, buf);
694 }
695}
696
697/**
698 * n_hdlc_alloc - allocate an n_hdlc instance data structure
699 *
700 * Returns a pointer to newly created structure if success, otherwise %NULL
701 */
702static struct n_hdlc *n_hdlc_alloc(void)
703{
704 struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL);
705
706 if (!n_hdlc)
707 return NULL;
708
709 spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);
710 spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
711 spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
712 spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
713
714 INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);
715 INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);
716 INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);
717 INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);
718
719 n_hdlc_alloc_buf(&n_hdlc->rx_free_buf_list, DEFAULT_RX_BUF_COUNT, "rx");
720 n_hdlc_alloc_buf(&n_hdlc->tx_free_buf_list, DEFAULT_TX_BUF_COUNT, "tx");
721
722 /* Initialize the control block */
723 n_hdlc->magic = HDLC_MAGIC;
724
725 return n_hdlc;
726
727} /* end of n_hdlc_alloc() */
728
729/**
730 * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
731 * @buf_list: pointer to the buffer list
732 * @buf: pointer to the buffer
733 */
734static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
735 struct n_hdlc_buf *buf)
736{
737 unsigned long flags;
738
739 spin_lock_irqsave(&buf_list->spinlock, flags);
740
741 list_add(&buf->list_item, &buf_list->list);
742 buf_list->count++;
743
744 spin_unlock_irqrestore(&buf_list->spinlock, flags);
745}
746
747/**
748 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
749 * @buf_list: pointer to buffer list
750 * @buf: pointer to buffer
751 */
752static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
753 struct n_hdlc_buf *buf)
754{
755 unsigned long flags;
756
757 spin_lock_irqsave(&buf_list->spinlock, flags);
758
759 list_add_tail(&buf->list_item, &buf_list->list);
760 buf_list->count++;
761
762 spin_unlock_irqrestore(&buf_list->spinlock, flags);
763} /* end of n_hdlc_buf_put() */
764
765/**
766 * n_hdlc_buf_get - remove and return an HDLC buffer from list
767 * @buf_list: pointer to HDLC buffer list
768 *
769 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
770 * list.
771 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
772 */
773static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
774{
775 unsigned long flags;
776 struct n_hdlc_buf *buf;
777
778 spin_lock_irqsave(&buf_list->spinlock, flags);
779
780 buf = list_first_entry_or_null(&buf_list->list,
781 struct n_hdlc_buf, list_item);
782 if (buf) {
783 list_del(&buf->list_item);
784 buf_list->count--;
785 }
786
787 spin_unlock_irqrestore(&buf_list->spinlock, flags);
788 return buf;
789} /* end of n_hdlc_buf_get() */
790
791static struct tty_ldisc_ops n_hdlc_ldisc = {
792 .owner = THIS_MODULE,
793 .num = N_HDLC,
794 .name = "hdlc",
795 .open = n_hdlc_tty_open,
796 .close = n_hdlc_tty_close,
797 .read = n_hdlc_tty_read,
798 .write = n_hdlc_tty_write,
799 .ioctl = n_hdlc_tty_ioctl,
800 .poll = n_hdlc_tty_poll,
801 .receive_buf = n_hdlc_tty_receive,
802 .write_wakeup = n_hdlc_tty_wakeup,
803 .flush_buffer = flush_rx_queue,
804};
805
806static int __init n_hdlc_init(void)
807{
808 int status;
809
810 /* range check maxframe arg */
811 maxframe = clamp(maxframe, 4096, MAX_HDLC_FRAME_SIZE);
812
813 status = tty_register_ldisc(&n_hdlc_ldisc);
814 if (!status)
815 pr_info("N_HDLC line discipline registered with maxframe=%d\n",
816 maxframe);
817 else
818 pr_err("N_HDLC: error registering line discipline: %d\n",
819 status);
820
821 return status;
822
823} /* end of init_module() */
824
825static void __exit n_hdlc_exit(void)
826{
827 tty_unregister_ldisc(&n_hdlc_ldisc);
828}
829
830module_init(n_hdlc_init);
831module_exit(n_hdlc_exit);
832
833MODULE_LICENSE("GPL");
834MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
835module_param(maxframe, int, 0);
836MODULE_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);