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(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 __set_current_state(TASK_RUNNING);
601 if (copy_to_user(buf, rbuf->buf, rbuf->count))
602 ret = -EFAULT;
603 else
604 ret = rbuf->count;
605 }
606
607 if (n_hdlc->rx_free_buf_list.count >
608 DEFAULT_RX_BUF_COUNT)
609 kfree(rbuf);
610 else
611 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
612 break;
613 }
614
615 /* no data */
616 if (tty_io_nonblock(tty, file)) {
617 ret = -EAGAIN;
618 break;
619 }
620
621 schedule();
622
623 if (signal_pending(current)) {
624 ret = -EINTR;
625 break;
626 }
627 }
628
629 remove_wait_queue(&tty->read_wait, &wait);
630 __set_current_state(TASK_RUNNING);
631
632 return ret;
633
634} /* end of n_hdlc_tty_read() */
635
636/**
637 * n_hdlc_tty_write - write a single frame of data to device
638 * @tty - pointer to associated tty device instance data
639 * @file - pointer to file object data
640 * @data - pointer to transmit data (one frame)
641 * @count - size of transmit frame in bytes
642 *
643 * Returns the number of bytes written (or error code).
644 */
645static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
646 const unsigned char *data, size_t count)
647{
648 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
649 int error = 0;
650 DECLARE_WAITQUEUE(wait, current);
651 struct n_hdlc_buf *tbuf;
652
653 if (debuglevel >= DEBUG_LEVEL_INFO)
654 printk("%s(%d)n_hdlc_tty_write() called count=%zd\n",
655 __FILE__,__LINE__,count);
656
657 /* Verify pointers */
658 if (!n_hdlc)
659 return -EIO;
660
661 if (n_hdlc->magic != HDLC_MAGIC)
662 return -EIO;
663
664 /* verify frame size */
665 if (count > maxframe ) {
666 if (debuglevel & DEBUG_LEVEL_INFO)
667 printk (KERN_WARNING
668 "n_hdlc_tty_write: truncating user packet "
669 "from %lu to %d\n", (unsigned long) count,
670 maxframe );
671 count = maxframe;
672 }
673
674 add_wait_queue(&tty->write_wait, &wait);
675
676 for (;;) {
677 set_current_state(TASK_INTERRUPTIBLE);
678
679 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
680 if (tbuf)
681 break;
682
683 if (tty_io_nonblock(tty, file)) {
684 error = -EAGAIN;
685 break;
686 }
687 schedule();
688
689 n_hdlc = tty2n_hdlc (tty);
690 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
691 tty != n_hdlc->tty) {
692 printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
693 error = -EIO;
694 break;
695 }
696
697 if (signal_pending(current)) {
698 error = -EINTR;
699 break;
700 }
701 }
702
703 __set_current_state(TASK_RUNNING);
704 remove_wait_queue(&tty->write_wait, &wait);
705
706 if (!error) {
707 /* Retrieve the user's buffer */
708 memcpy(tbuf->buf, data, count);
709
710 /* Send the data */
711 tbuf->count = error = count;
712 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
713 n_hdlc_send_frames(n_hdlc,tty);
714 }
715
716 return error;
717
718} /* end of n_hdlc_tty_write() */
719
720/**
721 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
722 * @tty - pointer to tty instance data
723 * @file - pointer to open file object for device
724 * @cmd - IOCTL command code
725 * @arg - argument for IOCTL call (cmd dependent)
726 *
727 * Returns command dependent result.
728 */
729static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
730 unsigned int cmd, unsigned long arg)
731{
732 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
733 int error = 0;
734 int count;
735 unsigned long flags;
736 struct n_hdlc_buf *buf = NULL;
737
738 if (debuglevel >= DEBUG_LEVEL_INFO)
739 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
740 __FILE__,__LINE__,cmd);
741
742 /* Verify the status of the device */
743 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
744 return -EBADF;
745
746 switch (cmd) {
747 case FIONREAD:
748 /* report count of read data available */
749 /* in next available frame (if any) */
750 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
751 buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
752 struct n_hdlc_buf, list_item);
753 if (buf)
754 count = buf->count;
755 else
756 count = 0;
757 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
758 error = put_user(count, (int __user *)arg);
759 break;
760
761 case TIOCOUTQ:
762 /* get the pending tx byte count in the driver */
763 count = tty_chars_in_buffer(tty);
764 /* add size of next output frame in queue */
765 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
766 buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
767 struct n_hdlc_buf, list_item);
768 if (buf)
769 count += buf->count;
770 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
771 error = put_user(count, (int __user *)arg);
772 break;
773
774 case TCFLSH:
775 switch (arg) {
776 case TCIOFLUSH:
777 case TCOFLUSH:
778 flush_tx_queue(tty);
779 }
780 /* fall through - to default */
781
782 default:
783 error = n_tty_ioctl_helper(tty, file, cmd, arg);
784 break;
785 }
786 return error;
787
788} /* end of n_hdlc_tty_ioctl() */
789
790/**
791 * n_hdlc_tty_poll - TTY callback for poll system call
792 * @tty - pointer to tty instance data
793 * @filp - pointer to open file object for device
794 * @poll_table - wait queue for operations
795 *
796 * Determine which operations (read/write) will not block and return info
797 * to caller.
798 * Returns a bit mask containing info on which ops will not block.
799 */
800static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
801 poll_table *wait)
802{
803 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
804 __poll_t mask = 0;
805
806 if (debuglevel >= DEBUG_LEVEL_INFO)
807 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
808
809 if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
810 /* queue current process into any wait queue that */
811 /* may awaken in the future (read and write) */
812
813 poll_wait(filp, &tty->read_wait, wait);
814 poll_wait(filp, &tty->write_wait, wait);
815
816 /* set bits for operations that won't block */
817 if (!list_empty(&n_hdlc->rx_buf_list.list))
818 mask |= EPOLLIN | EPOLLRDNORM; /* readable */
819 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
820 mask |= EPOLLHUP;
821 if (tty_hung_up_p(filp))
822 mask |= EPOLLHUP;
823 if (!tty_is_writelocked(tty) &&
824 !list_empty(&n_hdlc->tx_free_buf_list.list))
825 mask |= EPOLLOUT | EPOLLWRNORM; /* writable */
826 }
827 return mask;
828} /* end of n_hdlc_tty_poll() */
829
830/**
831 * n_hdlc_alloc - allocate an n_hdlc instance data structure
832 *
833 * Returns a pointer to newly created structure if success, otherwise %NULL
834 */
835static struct n_hdlc *n_hdlc_alloc(void)
836{
837 struct n_hdlc_buf *buf;
838 int i;
839 struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL);
840
841 if (!n_hdlc)
842 return NULL;
843
844 spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);
845 spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
846 spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
847 spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
848
849 INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);
850 INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);
851 INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);
852 INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);
853
854 /* allocate free rx buffer list */
855 for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
856 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
857 if (buf)
858 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
859 else if (debuglevel >= DEBUG_LEVEL_INFO)
860 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
861 }
862
863 /* allocate free tx buffer list */
864 for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
865 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
866 if (buf)
867 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
868 else if (debuglevel >= DEBUG_LEVEL_INFO)
869 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
870 }
871
872 /* Initialize the control block */
873 n_hdlc->magic = HDLC_MAGIC;
874 n_hdlc->flags = 0;
875
876 return n_hdlc;
877
878} /* end of n_hdlc_alloc() */
879
880/**
881 * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
882 * @buf_list - pointer to the buffer list
883 * @buf - pointer to the buffer
884 */
885static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
886 struct n_hdlc_buf *buf)
887{
888 unsigned long flags;
889
890 spin_lock_irqsave(&buf_list->spinlock, flags);
891
892 list_add(&buf->list_item, &buf_list->list);
893 buf_list->count++;
894
895 spin_unlock_irqrestore(&buf_list->spinlock, flags);
896}
897
898/**
899 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
900 * @buf_list - pointer to buffer list
901 * @buf - pointer to buffer
902 */
903static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
904 struct n_hdlc_buf *buf)
905{
906 unsigned long flags;
907
908 spin_lock_irqsave(&buf_list->spinlock, flags);
909
910 list_add_tail(&buf->list_item, &buf_list->list);
911 buf_list->count++;
912
913 spin_unlock_irqrestore(&buf_list->spinlock, flags);
914} /* end of n_hdlc_buf_put() */
915
916/**
917 * n_hdlc_buf_get - remove and return an HDLC buffer from list
918 * @buf_list - pointer to HDLC buffer list
919 *
920 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
921 * list.
922 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
923 */
924static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
925{
926 unsigned long flags;
927 struct n_hdlc_buf *buf;
928
929 spin_lock_irqsave(&buf_list->spinlock, flags);
930
931 buf = list_first_entry_or_null(&buf_list->list,
932 struct n_hdlc_buf, list_item);
933 if (buf) {
934 list_del(&buf->list_item);
935 buf_list->count--;
936 }
937
938 spin_unlock_irqrestore(&buf_list->spinlock, flags);
939 return buf;
940} /* end of n_hdlc_buf_get() */
941
942static const char hdlc_banner[] __initconst =
943 KERN_INFO "HDLC line discipline maxframe=%u\n";
944static const char hdlc_register_ok[] __initconst =
945 KERN_INFO "N_HDLC line discipline registered.\n";
946static const char hdlc_register_fail[] __initconst =
947 KERN_ERR "error registering line discipline: %d\n";
948
949static int __init n_hdlc_init(void)
950{
951 int status;
952
953 /* range check maxframe arg */
954 if (maxframe < 4096)
955 maxframe = 4096;
956 else if (maxframe > 65535)
957 maxframe = 65535;
958
959 printk(hdlc_banner, maxframe);
960
961 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
962 if (!status)
963 printk(hdlc_register_ok);
964 else
965 printk(hdlc_register_fail, status);
966
967 return status;
968
969} /* end of init_module() */
970
971static const char hdlc_unregister_ok[] __exitdata =
972 KERN_INFO "N_HDLC: line discipline unregistered\n";
973static const char hdlc_unregister_fail[] __exitdata =
974 KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
975
976static void __exit n_hdlc_exit(void)
977{
978 /* Release tty registration of line discipline */
979 int status = tty_unregister_ldisc(N_HDLC);
980
981 if (status)
982 printk(hdlc_unregister_fail, status);
983 else
984 printk(hdlc_unregister_ok);
985}
986
987module_init(n_hdlc_init);
988module_exit(n_hdlc_exit);
989
990MODULE_LICENSE("GPL");
991MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
992module_param(debuglevel, int, 0);
993module_param(maxframe, int, 0);
994MODULE_ALIAS_LDISC(N_HDLC);
995