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
116 struct n_hdlc_buf {
117 struct list_head list_item;
118 int count;
119 char buf[1];
120 };
121
122 #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
123
124 struct n_hdlc_buf_list {
125 struct list_head list;
126 int count;
127 spinlock_t spinlock;
128 };
129
130 /**
131 * struct n_hdlc - per device instance data structure
132 * @magic - magic value for structure
133 * @flags - miscellaneous control flags
134 * @tty - ptr to TTY structure
135 * @backup_tty - TTY to use if tty gets closed
136 * @tbusy - reentrancy flag for tx wakeup code
137 * @woke_up - FIXME: describe this field
138 * @tx_buf_list - list of pending transmit frame buffers
139 * @rx_buf_list - list of received frame buffers
140 * @tx_free_buf_list - list unused transmit frame buffers
141 * @rx_free_buf_list - list unused received frame buffers
142 */
143 struct n_hdlc {
144 int magic;
145 __u32 flags;
146 struct tty_struct *tty;
147 struct tty_struct *backup_tty;
148 int tbusy;
149 int woke_up;
150 struct n_hdlc_buf_list tx_buf_list;
151 struct n_hdlc_buf_list rx_buf_list;
152 struct n_hdlc_buf_list tx_free_buf_list;
153 struct n_hdlc_buf_list rx_free_buf_list;
154 };
155
156 /*
157 * HDLC buffer list manipulation functions
158 */
159 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
160 struct n_hdlc_buf *buf);
161 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
162 struct n_hdlc_buf *buf);
163 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
164
165 /* Local functions */
166
167 static struct n_hdlc *n_hdlc_alloc (void);
168
169 /* debug level can be set by insmod for debugging purposes */
170 #define DEBUG_LEVEL_INFO 1
171 static int debuglevel;
172
173 /* max frame size for memory allocations */
174 static int maxframe = 4096;
175
176 /* TTY callbacks */
177
178 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
179 __u8 __user *buf, size_t nr);
180 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
181 const unsigned char *buf, size_t nr);
182 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
183 unsigned int cmd, unsigned long arg);
184 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
185 poll_table *wait);
186 static int n_hdlc_tty_open(struct tty_struct *tty);
187 static void n_hdlc_tty_close(struct tty_struct *tty);
188 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
189 char *fp, int count);
190 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
191
192 #define bset(p,b) ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
193
194 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
195 #define n_hdlc2tty(n_hdlc) ((n_hdlc)->tty)
196
flush_rx_queue(struct tty_struct * tty)197 static void flush_rx_queue(struct tty_struct *tty)
198 {
199 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
200 struct n_hdlc_buf *buf;
201
202 while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
203 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
204 }
205
flush_tx_queue(struct tty_struct * tty)206 static void flush_tx_queue(struct tty_struct *tty)
207 {
208 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
209 struct n_hdlc_buf *buf;
210
211 while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
212 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
213 }
214
215 static struct tty_ldisc_ops n_hdlc_ldisc = {
216 .owner = THIS_MODULE,
217 .magic = TTY_LDISC_MAGIC,
218 .name = "hdlc",
219 .open = n_hdlc_tty_open,
220 .close = n_hdlc_tty_close,
221 .read = n_hdlc_tty_read,
222 .write = n_hdlc_tty_write,
223 .ioctl = n_hdlc_tty_ioctl,
224 .poll = n_hdlc_tty_poll,
225 .receive_buf = n_hdlc_tty_receive,
226 .write_wakeup = n_hdlc_tty_wakeup,
227 .flush_buffer = flush_rx_queue,
228 };
229
230 /**
231 * n_hdlc_release - release an n_hdlc per device line discipline info structure
232 * @n_hdlc - per device line discipline info structure
233 */
n_hdlc_release(struct n_hdlc * n_hdlc)234 static void n_hdlc_release(struct n_hdlc *n_hdlc)
235 {
236 struct tty_struct *tty = n_hdlc2tty (n_hdlc);
237 struct n_hdlc_buf *buf;
238
239 if (debuglevel >= DEBUG_LEVEL_INFO)
240 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
241
242 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
243 wake_up_interruptible (&tty->read_wait);
244 wake_up_interruptible (&tty->write_wait);
245
246 if (tty->disc_data == n_hdlc)
247 tty->disc_data = NULL; /* Break the tty->n_hdlc link */
248
249 /* Release transmit and receive buffers */
250 for(;;) {
251 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
252 if (buf) {
253 kfree(buf);
254 } else
255 break;
256 }
257 for(;;) {
258 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
259 if (buf) {
260 kfree(buf);
261 } else
262 break;
263 }
264 for(;;) {
265 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
266 if (buf) {
267 kfree(buf);
268 } else
269 break;
270 }
271 for(;;) {
272 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
273 if (buf) {
274 kfree(buf);
275 } else
276 break;
277 }
278 kfree(n_hdlc);
279
280 } /* end of n_hdlc_release() */
281
282 /**
283 * n_hdlc_tty_close - line discipline close
284 * @tty - pointer to tty info structure
285 *
286 * Called when the line discipline is changed to something
287 * else, the tty is closed, or the tty detects a hangup.
288 */
n_hdlc_tty_close(struct tty_struct * tty)289 static void n_hdlc_tty_close(struct tty_struct *tty)
290 {
291 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
292
293 if (debuglevel >= DEBUG_LEVEL_INFO)
294 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
295
296 if (n_hdlc != NULL) {
297 if (n_hdlc->magic != HDLC_MAGIC) {
298 printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
299 return;
300 }
301 #if defined(TTY_NO_WRITE_SPLIT)
302 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
303 #endif
304 tty->disc_data = NULL;
305 if (tty == n_hdlc->backup_tty)
306 n_hdlc->backup_tty = NULL;
307 if (tty != n_hdlc->tty)
308 return;
309 if (n_hdlc->backup_tty) {
310 n_hdlc->tty = n_hdlc->backup_tty;
311 } else {
312 n_hdlc_release (n_hdlc);
313 }
314 }
315
316 if (debuglevel >= DEBUG_LEVEL_INFO)
317 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
318
319 } /* end of n_hdlc_tty_close() */
320
321 /**
322 * n_hdlc_tty_open - called when line discipline changed to n_hdlc
323 * @tty - pointer to tty info structure
324 *
325 * Returns 0 if success, otherwise error code
326 */
n_hdlc_tty_open(struct tty_struct * tty)327 static int n_hdlc_tty_open (struct tty_struct *tty)
328 {
329 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
330
331 if (debuglevel >= DEBUG_LEVEL_INFO)
332 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
333 __FILE__,__LINE__,
334 tty->name);
335
336 /* There should not be an existing table for this slot. */
337 if (n_hdlc) {
338 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
339 return -EEXIST;
340 }
341
342 n_hdlc = n_hdlc_alloc();
343 if (!n_hdlc) {
344 printk (KERN_ERR "n_hdlc_alloc failed\n");
345 return -ENFILE;
346 }
347
348 tty->disc_data = n_hdlc;
349 n_hdlc->tty = tty;
350 tty->receive_room = 65536;
351
352 #if defined(TTY_NO_WRITE_SPLIT)
353 /* change tty_io write() to not split large writes into 8K chunks */
354 set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
355 #endif
356
357 /* flush receive data from driver */
358 tty_driver_flush_buffer(tty);
359
360 if (debuglevel >= DEBUG_LEVEL_INFO)
361 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
362
363 return 0;
364
365 } /* end of n_tty_hdlc_open() */
366
367 /**
368 * n_hdlc_send_frames - send frames on pending send buffer list
369 * @n_hdlc - pointer to ldisc instance data
370 * @tty - pointer to tty instance data
371 *
372 * Send frames on pending send buffer list until the driver does not accept a
373 * frame (busy) this function is called after adding a frame to the send buffer
374 * list and by the tty wakeup callback.
375 */
n_hdlc_send_frames(struct n_hdlc * n_hdlc,struct tty_struct * tty)376 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
377 {
378 register int actual;
379 unsigned long flags;
380 struct n_hdlc_buf *tbuf;
381
382 if (debuglevel >= DEBUG_LEVEL_INFO)
383 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
384 check_again:
385
386 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
387 if (n_hdlc->tbusy) {
388 n_hdlc->woke_up = 1;
389 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
390 return;
391 }
392 n_hdlc->tbusy = 1;
393 n_hdlc->woke_up = 0;
394 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
395
396 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
397 while (tbuf) {
398 if (debuglevel >= DEBUG_LEVEL_INFO)
399 printk("%s(%d)sending frame %p, count=%d\n",
400 __FILE__,__LINE__,tbuf,tbuf->count);
401
402 /* Send the next block of data to device */
403 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
404 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
405
406 /* rollback was possible and has been done */
407 if (actual == -ERESTARTSYS) {
408 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
409 break;
410 }
411 /* if transmit error, throw frame away by */
412 /* pretending it was accepted by driver */
413 if (actual < 0)
414 actual = tbuf->count;
415
416 if (actual == tbuf->count) {
417 if (debuglevel >= DEBUG_LEVEL_INFO)
418 printk("%s(%d)frame %p completed\n",
419 __FILE__,__LINE__,tbuf);
420
421 /* free current transmit buffer */
422 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
423
424 /* wait up sleeping writers */
425 wake_up_interruptible(&tty->write_wait);
426
427 /* get next pending transmit buffer */
428 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
429 } else {
430 if (debuglevel >= DEBUG_LEVEL_INFO)
431 printk("%s(%d)frame %p pending\n",
432 __FILE__,__LINE__,tbuf);
433
434 /*
435 * the buffer was not accepted by driver,
436 * return it back into tx queue
437 */
438 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
439 break;
440 }
441 }
442
443 if (!tbuf)
444 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
445
446 /* Clear the re-entry flag */
447 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
448 n_hdlc->tbusy = 0;
449 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
450
451 if (n_hdlc->woke_up)
452 goto check_again;
453
454 if (debuglevel >= DEBUG_LEVEL_INFO)
455 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
456
457 } /* end of n_hdlc_send_frames() */
458
459 /**
460 * n_hdlc_tty_wakeup - Callback for transmit wakeup
461 * @tty - pointer to associated tty instance data
462 *
463 * Called when low level device driver can accept more send data.
464 */
n_hdlc_tty_wakeup(struct tty_struct * tty)465 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
466 {
467 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
468
469 if (debuglevel >= DEBUG_LEVEL_INFO)
470 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
471
472 if (!n_hdlc)
473 return;
474
475 if (tty != n_hdlc->tty) {
476 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
477 return;
478 }
479
480 n_hdlc_send_frames (n_hdlc, tty);
481
482 } /* end of n_hdlc_tty_wakeup() */
483
484 /**
485 * n_hdlc_tty_receive - Called by tty driver when receive data is available
486 * @tty - pointer to tty instance data
487 * @data - pointer to received data
488 * @flags - pointer to flags for data
489 * @count - count of received data in bytes
490 *
491 * Called by tty low level driver when receive data is available. Data is
492 * interpreted as one HDLC frame.
493 */
n_hdlc_tty_receive(struct tty_struct * tty,const __u8 * data,char * flags,int count)494 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
495 char *flags, int count)
496 {
497 register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
498 register struct n_hdlc_buf *buf;
499
500 if (debuglevel >= DEBUG_LEVEL_INFO)
501 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
502 __FILE__,__LINE__, count);
503
504 /* This can happen if stuff comes in on the backup tty */
505 if (!n_hdlc || tty != n_hdlc->tty)
506 return;
507
508 /* verify line is using HDLC discipline */
509 if (n_hdlc->magic != HDLC_MAGIC) {
510 printk("%s(%d) line not using HDLC discipline\n",
511 __FILE__,__LINE__);
512 return;
513 }
514
515 if ( count>maxframe ) {
516 if (debuglevel >= DEBUG_LEVEL_INFO)
517 printk("%s(%d) rx count>maxframesize, data discarded\n",
518 __FILE__,__LINE__);
519 return;
520 }
521
522 /* get a free HDLC buffer */
523 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
524 if (!buf) {
525 /* no buffers in free list, attempt to allocate another rx buffer */
526 /* unless the maximum count has been reached */
527 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
528 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
529 }
530
531 if (!buf) {
532 if (debuglevel >= DEBUG_LEVEL_INFO)
533 printk("%s(%d) no more rx buffers, data discarded\n",
534 __FILE__,__LINE__);
535 return;
536 }
537
538 /* copy received data to HDLC buffer */
539 memcpy(buf->buf,data,count);
540 buf->count=count;
541
542 /* add HDLC buffer to list of received frames */
543 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
544
545 /* wake up any blocked reads and perform async signalling */
546 wake_up_interruptible (&tty->read_wait);
547 if (n_hdlc->tty->fasync != NULL)
548 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
549
550 } /* end of n_hdlc_tty_receive() */
551
552 /**
553 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
554 * @tty - pointer to tty instance data
555 * @file - pointer to open file object
556 * @buf - pointer to returned data buffer
557 * @nr - size of returned data buffer
558 *
559 * Returns the number of bytes returned or error code.
560 */
n_hdlc_tty_read(struct tty_struct * tty,struct file * file,__u8 __user * buf,size_t nr)561 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
562 __u8 __user *buf, size_t nr)
563 {
564 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
565 int ret = 0;
566 struct n_hdlc_buf *rbuf;
567 DECLARE_WAITQUEUE(wait, current);
568
569 if (debuglevel >= DEBUG_LEVEL_INFO)
570 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
571
572 /* Validate the pointers */
573 if (!n_hdlc)
574 return -EIO;
575
576 /* verify user access to buffer */
577 if (!access_ok(VERIFY_WRITE, buf, nr)) {
578 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
579 "buffer\n", __FILE__, __LINE__);
580 return -EFAULT;
581 }
582
583 add_wait_queue(&tty->read_wait, &wait);
584
585 for (;;) {
586 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
587 ret = -EIO;
588 break;
589 }
590 if (tty_hung_up_p(file))
591 break;
592
593 set_current_state(TASK_INTERRUPTIBLE);
594
595 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
596 if (rbuf) {
597 if (rbuf->count > nr) {
598 /* too large for caller's buffer */
599 ret = -EOVERFLOW;
600 } else {
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 (file->f_flags & O_NONBLOCK) {
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 */
n_hdlc_tty_write(struct tty_struct * tty,struct file * file,const unsigned char * data,size_t count)645 static 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 (file->f_flags & O_NONBLOCK) {
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 */
n_hdlc_tty_ioctl(struct tty_struct * tty,struct file * file,unsigned int cmd,unsigned long arg)729 static 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 */
n_hdlc_tty_poll(struct tty_struct * tty,struct file * filp,poll_table * wait)800 static unsigned int 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 unsigned int 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 |= POLLIN | POLLRDNORM; /* readable */
819 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
820 mask |= POLLHUP;
821 if (tty_hung_up_p(filp))
822 mask |= POLLHUP;
823 if (!tty_is_writelocked(tty) &&
824 !list_empty(&n_hdlc->tx_free_buf_list.list))
825 mask |= POLLOUT | POLLWRNORM; /* 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 */
n_hdlc_alloc(void)835 static struct n_hdlc *n_hdlc_alloc(void)
836 {
837 struct n_hdlc_buf *buf;
838 int i;
839 struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
840
841 if (!n_hdlc)
842 return NULL;
843
844 memset(n_hdlc, 0, sizeof(*n_hdlc));
845
846 spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);
847 spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
848 spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
849 spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
850
851 INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);
852 INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);
853 INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);
854 INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);
855
856 /* allocate free rx buffer list */
857 for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
858 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
859 if (buf)
860 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
861 else if (debuglevel >= DEBUG_LEVEL_INFO)
862 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
863 }
864
865 /* allocate free tx buffer list */
866 for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
867 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
868 if (buf)
869 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
870 else if (debuglevel >= DEBUG_LEVEL_INFO)
871 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
872 }
873
874 /* Initialize the control block */
875 n_hdlc->magic = HDLC_MAGIC;
876 n_hdlc->flags = 0;
877
878 return n_hdlc;
879
880 } /* end of n_hdlc_alloc() */
881
882 /**
883 * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
884 * @buf_list - pointer to the buffer list
885 * @buf - pointer to the buffer
886 */
n_hdlc_buf_return(struct n_hdlc_buf_list * buf_list,struct n_hdlc_buf * buf)887 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
888 struct n_hdlc_buf *buf)
889 {
890 unsigned long flags;
891
892 spin_lock_irqsave(&buf_list->spinlock, flags);
893
894 list_add(&buf->list_item, &buf_list->list);
895 buf_list->count++;
896
897 spin_unlock_irqrestore(&buf_list->spinlock, flags);
898 }
899
900 /**
901 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
902 * @buf_list - pointer to buffer list
903 * @buf - pointer to buffer
904 */
n_hdlc_buf_put(struct n_hdlc_buf_list * buf_list,struct n_hdlc_buf * buf)905 static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
906 struct n_hdlc_buf *buf)
907 {
908 unsigned long flags;
909
910 spin_lock_irqsave(&buf_list->spinlock, flags);
911
912 list_add_tail(&buf->list_item, &buf_list->list);
913 buf_list->count++;
914
915 spin_unlock_irqrestore(&buf_list->spinlock, flags);
916 } /* end of n_hdlc_buf_put() */
917
918 /**
919 * n_hdlc_buf_get - remove and return an HDLC buffer from list
920 * @buf_list - pointer to HDLC buffer list
921 *
922 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
923 * list.
924 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
925 */
n_hdlc_buf_get(struct n_hdlc_buf_list * buf_list)926 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
927 {
928 unsigned long flags;
929 struct n_hdlc_buf *buf;
930
931 spin_lock_irqsave(&buf_list->spinlock, flags);
932
933 buf = list_first_entry_or_null(&buf_list->list,
934 struct n_hdlc_buf, list_item);
935 if (buf) {
936 list_del(&buf->list_item);
937 buf_list->count--;
938 }
939
940 spin_unlock_irqrestore(&buf_list->spinlock, flags);
941 return buf;
942 } /* end of n_hdlc_buf_get() */
943
944 static char hdlc_banner[] __initdata =
945 KERN_INFO "HDLC line discipline maxframe=%u\n";
946 static char hdlc_register_ok[] __initdata =
947 KERN_INFO "N_HDLC line discipline registered.\n";
948 static char hdlc_register_fail[] __initdata =
949 KERN_ERR "error registering line discipline: %d\n";
950 static char hdlc_init_fail[] __initdata =
951 KERN_INFO "N_HDLC: init failure %d\n";
952
n_hdlc_init(void)953 static int __init n_hdlc_init(void)
954 {
955 int status;
956
957 /* range check maxframe arg */
958 if (maxframe < 4096)
959 maxframe = 4096;
960 else if (maxframe > 65535)
961 maxframe = 65535;
962
963 printk(hdlc_banner, maxframe);
964
965 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
966 if (!status)
967 printk(hdlc_register_ok);
968 else
969 printk(hdlc_register_fail, status);
970
971 if (status)
972 printk(hdlc_init_fail, status);
973 return status;
974
975 } /* end of init_module() */
976
977 static char hdlc_unregister_ok[] __exitdata =
978 KERN_INFO "N_HDLC: line discipline unregistered\n";
979 static char hdlc_unregister_fail[] __exitdata =
980 KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
981
n_hdlc_exit(void)982 static void __exit n_hdlc_exit(void)
983 {
984 /* Release tty registration of line discipline */
985 int status = tty_unregister_ldisc(N_HDLC);
986
987 if (status)
988 printk(hdlc_unregister_fail, status);
989 else
990 printk(hdlc_unregister_ok);
991 }
992
993 module_init(n_hdlc_init);
994 module_exit(n_hdlc_exit);
995
996 MODULE_LICENSE("GPL");
997 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
998 module_param(debuglevel, int, 0);
999 module_param(maxframe, int, 0);
1000 MODULE_ALIAS_LDISC(N_HDLC);
1001