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