blob: 82bcfb9c839adb62a4cca24c10c55c20c8c72cf4 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* 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 * $Id: n_hdlc.c,v 4.8 2003/05/06 21:18:51 paulkf Exp $
14 *
15 * This code is released under the GNU General Public License (GPL)
16 *
17 * This module implements the tty line discipline N_HDLC for use with
18 * tty device drivers that support bit-synchronous HDLC communications.
19 *
20 * All HDLC data is frame oriented which means:
21 *
22 * 1. tty write calls represent one complete transmit frame of data
23 * The device driver should accept the complete frame or none of
24 * the frame (busy) in the write method. Each write call should have
25 * a byte count in the range of 2-65535 bytes (2 is min HDLC frame
26 * with 1 addr byte and 1 ctrl byte). The max byte count of 65535
27 * should include any crc bytes required. For example, when using
28 * CCITT CRC32, 4 crc bytes are required, so the maximum size frame
29 * the application may transmit is limited to 65531 bytes. For CCITT
30 * CRC16, the maximum application frame size would be 65533.
31 *
32 *
33 * 2. receive callbacks from the device driver represents
34 * one received frame. The device driver should bypass
35 * the tty flip buffer and call the line discipline receive
36 * callback directly to avoid fragmenting or concatenating
37 * multiple frames into a single receive callback.
38 *
39 * The HDLC line discipline queues the receive frames in separate
40 * buffers so complete receive frames can be returned by the
41 * tty read calls.
42 *
43 * 3. tty read calls returns an entire frame of data or nothing.
44 *
45 * 4. all send and receive data is considered raw. No processing
46 * or translation is performed by the line discipline, regardless
47 * of the tty flags
48 *
49 * 5. When line discipline is queried for the amount of receive
50 * data available (FIOC), 0 is returned if no data available,
51 * otherwise the count of the next available frame is returned.
52 * (instead of the sum of all received frame counts).
53 *
54 * These conventions allow the standard tty programming interface
55 * to be used for synchronous HDLC applications when used with
56 * this line discipline (or another line discipline that is frame
57 * oriented such as N_PPP).
58 *
59 * The SyncLink driver (synclink.c) implements both asynchronous
60 * (using standard line discipline N_TTY) and synchronous HDLC
61 * (using N_HDLC) communications, with the latter using the above
62 * conventions.
63 *
64 * This implementation is very basic and does not maintain
65 * any statistics. The main point is to enforce the raw data
66 * and frame orientation of HDLC communications.
67 *
68 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
69 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
70 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
71 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
72 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
73 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
74 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
75 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
76 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
77 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
78 * OF THE POSSIBILITY OF SUCH DAMAGE.
79 */
80
81#define HDLC_MAGIC 0x239e
82#define HDLC_VERSION "$Revision: 4.8 $"
83
Linus Torvalds1da177e2005-04-16 15:20:36 -070084#include <linux/module.h>
85#include <linux/init.h>
86#include <linux/kernel.h>
87#include <linux/sched.h>
88#include <linux/types.h>
89#include <linux/fcntl.h>
90#include <linux/interrupt.h>
91#include <linux/ptrace.h>
92
93#undef VERSION
94#define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
95
96#include <linux/poll.h>
97#include <linux/in.h>
98#include <linux/ioctl.h>
99#include <linux/slab.h>
100#include <linux/tty.h>
101#include <linux/errno.h>
102#include <linux/string.h> /* used in new tty drivers */
103#include <linux/signal.h> /* used in new tty drivers */
104#include <linux/if.h>
105#include <linux/bitops.h>
106
107#include <asm/system.h>
108#include <asm/termios.h>
109#include <asm/uaccess.h>
110
111/*
112 * Buffers for individual HDLC frames
113 */
114#define MAX_HDLC_FRAME_SIZE 65535
115#define DEFAULT_RX_BUF_COUNT 10
116#define MAX_RX_BUF_COUNT 60
117#define DEFAULT_TX_BUF_COUNT 1
118
119struct n_hdlc_buf {
120 struct n_hdlc_buf *link;
121 int count;
122 char buf[1];
123};
124
125#define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
126
127struct n_hdlc_buf_list {
128 struct n_hdlc_buf *head;
129 struct n_hdlc_buf *tail;
130 int count;
131 spinlock_t spinlock;
132};
133
134/**
135 * struct n_hdlc - per device instance data structure
136 * @magic - magic value for structure
137 * @flags - miscellaneous control flags
138 * @tty - ptr to TTY structure
139 * @backup_tty - TTY to use if tty gets closed
140 * @tbusy - reentrancy flag for tx wakeup code
141 * @woke_up - FIXME: describe this field
142 * @tbuf - currently transmitting tx buffer
143 * @tx_buf_list - list of pending transmit frame buffers
144 * @rx_buf_list - list of received frame buffers
145 * @tx_free_buf_list - list unused transmit frame buffers
146 * @rx_free_buf_list - list unused received frame buffers
147 */
148struct n_hdlc {
149 int magic;
150 __u32 flags;
151 struct tty_struct *tty;
152 struct tty_struct *backup_tty;
153 int tbusy;
154 int woke_up;
155 struct n_hdlc_buf *tbuf;
156 struct n_hdlc_buf_list tx_buf_list;
157 struct n_hdlc_buf_list rx_buf_list;
158 struct n_hdlc_buf_list tx_free_buf_list;
159 struct n_hdlc_buf_list rx_free_buf_list;
160};
161
162/*
163 * HDLC buffer list manipulation functions
164 */
165static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list);
166static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
167 struct n_hdlc_buf *buf);
168static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
169
170/* Local functions */
171
172static struct n_hdlc *n_hdlc_alloc (void);
173
174/* debug level can be set by insmod for debugging purposes */
175#define DEBUG_LEVEL_INFO 1
176static int debuglevel;
177
178/* max frame size for memory allocations */
179static int maxframe = 4096;
180
181/* TTY callbacks */
182
183static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
184 __u8 __user *buf, size_t nr);
185static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
186 const unsigned char *buf, size_t nr);
187static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
188 unsigned int cmd, unsigned long arg);
189static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
190 poll_table *wait);
191static int n_hdlc_tty_open(struct tty_struct *tty);
192static void n_hdlc_tty_close(struct tty_struct *tty);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
194 char *fp, int count);
195static void n_hdlc_tty_wakeup(struct tty_struct *tty);
196
197#define bset(p,b) ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
198
199#define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
200#define n_hdlc2tty(n_hdlc) ((n_hdlc)->tty)
201
202static struct tty_ldisc n_hdlc_ldisc = {
203 .owner = THIS_MODULE,
204 .magic = TTY_LDISC_MAGIC,
205 .name = "hdlc",
206 .open = n_hdlc_tty_open,
207 .close = n_hdlc_tty_close,
208 .read = n_hdlc_tty_read,
209 .write = n_hdlc_tty_write,
210 .ioctl = n_hdlc_tty_ioctl,
211 .poll = n_hdlc_tty_poll,
212 .receive_buf = n_hdlc_tty_receive,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213 .write_wakeup = n_hdlc_tty_wakeup,
214};
215
216/**
217 * n_hdlc_release - release an n_hdlc per device line discipline info structure
218 * @n_hdlc - per device line discipline info structure
219 */
220static void n_hdlc_release(struct n_hdlc *n_hdlc)
221{
222 struct tty_struct *tty = n_hdlc2tty (n_hdlc);
223 struct n_hdlc_buf *buf;
224
225 if (debuglevel >= DEBUG_LEVEL_INFO)
226 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
227
228 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
229 wake_up_interruptible (&tty->read_wait);
230 wake_up_interruptible (&tty->write_wait);
231
Adrian Bunk827afdf2007-10-16 23:29:25 -0700232 if (tty->disc_data == n_hdlc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233 tty->disc_data = NULL; /* Break the tty->n_hdlc link */
234
235 /* Release transmit and receive buffers */
236 for(;;) {
237 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
238 if (buf) {
239 kfree(buf);
240 } else
241 break;
242 }
243 for(;;) {
244 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
245 if (buf) {
246 kfree(buf);
247 } else
248 break;
249 }
250 for(;;) {
251 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
252 if (buf) {
253 kfree(buf);
254 } else
255 break;
256 }
257 for(;;) {
258 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
259 if (buf) {
260 kfree(buf);
261 } else
262 break;
263 }
Jesper Juhl735d5662005-11-07 01:01:29 -0800264 kfree(n_hdlc->tbuf);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700265 kfree(n_hdlc);
266
267} /* end of n_hdlc_release() */
268
269/**
270 * n_hdlc_tty_close - line discipline close
271 * @tty - pointer to tty info structure
272 *
273 * Called when the line discipline is changed to something
274 * else, the tty is closed, or the tty detects a hangup.
275 */
276static void n_hdlc_tty_close(struct tty_struct *tty)
277{
278 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
279
280 if (debuglevel >= DEBUG_LEVEL_INFO)
281 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
282
283 if (n_hdlc != NULL) {
284 if (n_hdlc->magic != HDLC_MAGIC) {
285 printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
286 return;
287 }
288#if defined(TTY_NO_WRITE_SPLIT)
289 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
290#endif
291 tty->disc_data = NULL;
292 if (tty == n_hdlc->backup_tty)
293 n_hdlc->backup_tty = NULL;
294 if (tty != n_hdlc->tty)
295 return;
296 if (n_hdlc->backup_tty) {
297 n_hdlc->tty = n_hdlc->backup_tty;
298 } else {
299 n_hdlc_release (n_hdlc);
300 }
301 }
302
303 if (debuglevel >= DEBUG_LEVEL_INFO)
304 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
305
306} /* end of n_hdlc_tty_close() */
307
308/**
309 * n_hdlc_tty_open - called when line discipline changed to n_hdlc
310 * @tty - pointer to tty info structure
311 *
312 * Returns 0 if success, otherwise error code
313 */
314static int n_hdlc_tty_open (struct tty_struct *tty)
315{
316 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
317
318 if (debuglevel >= DEBUG_LEVEL_INFO)
319 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
320 __FILE__,__LINE__,
321 tty->name);
322
323 /* There should not be an existing table for this slot. */
324 if (n_hdlc) {
325 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
326 return -EEXIST;
327 }
328
329 n_hdlc = n_hdlc_alloc();
330 if (!n_hdlc) {
331 printk (KERN_ERR "n_hdlc_alloc failed\n");
332 return -ENFILE;
333 }
334
335 tty->disc_data = n_hdlc;
336 n_hdlc->tty = tty;
Alan Cox33f0f882006-01-09 20:54:13 -0800337 tty->receive_room = 65536;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700338
339#if defined(TTY_NO_WRITE_SPLIT)
340 /* change tty_io write() to not split large writes into 8K chunks */
341 set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
342#endif
343
344 /* Flush any pending characters in the driver and discipline. */
345
346 if (tty->ldisc.flush_buffer)
347 tty->ldisc.flush_buffer (tty);
348
349 if (tty->driver->flush_buffer)
350 tty->driver->flush_buffer (tty);
351
352 if (debuglevel >= DEBUG_LEVEL_INFO)
353 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
354
355 return 0;
356
357} /* end of n_tty_hdlc_open() */
358
359/**
360 * n_hdlc_send_frames - send frames on pending send buffer list
361 * @n_hdlc - pointer to ldisc instance data
362 * @tty - pointer to tty instance data
363 *
364 * Send frames on pending send buffer list until the driver does not accept a
365 * frame (busy) this function is called after adding a frame to the send buffer
366 * list and by the tty wakeup callback.
367 */
368static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
369{
370 register int actual;
371 unsigned long flags;
372 struct n_hdlc_buf *tbuf;
373
374 if (debuglevel >= DEBUG_LEVEL_INFO)
375 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
376 check_again:
377
378 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
379 if (n_hdlc->tbusy) {
380 n_hdlc->woke_up = 1;
381 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
382 return;
383 }
384 n_hdlc->tbusy = 1;
385 n_hdlc->woke_up = 0;
386 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
387
388 /* get current transmit buffer or get new transmit */
389 /* buffer from list of pending transmit buffers */
390
391 tbuf = n_hdlc->tbuf;
392 if (!tbuf)
393 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
394
395 while (tbuf) {
396 if (debuglevel >= DEBUG_LEVEL_INFO)
397 printk("%s(%d)sending frame %p, count=%d\n",
398 __FILE__,__LINE__,tbuf,tbuf->count);
399
400 /* Send the next block of data to device */
401 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
402 actual = tty->driver->write(tty, tbuf->buf, tbuf->count);
Jiri Slabyb0fed312007-07-15 23:40:12 -0700403
404 /* rollback was possible and has been done */
405 if (actual == -ERESTARTSYS) {
406 n_hdlc->tbuf = tbuf;
407 break;
408 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700409 /* if transmit error, throw frame away by */
410 /* pretending it was accepted by driver */
411 if (actual < 0)
412 actual = tbuf->count;
413
414 if (actual == tbuf->count) {
415 if (debuglevel >= DEBUG_LEVEL_INFO)
416 printk("%s(%d)frame %p completed\n",
417 __FILE__,__LINE__,tbuf);
418
419 /* free current transmit buffer */
420 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
421
422 /* this tx buffer is done */
423 n_hdlc->tbuf = NULL;
424
425 /* wait up sleeping writers */
426 wake_up_interruptible(&tty->write_wait);
427
428 /* get next pending transmit buffer */
429 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
430 } else {
431 if (debuglevel >= DEBUG_LEVEL_INFO)
432 printk("%s(%d)frame %p pending\n",
433 __FILE__,__LINE__,tbuf);
434
435 /* buffer not accepted by driver */
436 /* set this buffer as pending buffer */
437 n_hdlc->tbuf = tbuf;
438 break;
439 }
440 }
441
442 if (!tbuf)
443 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
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 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
476 return;
477 }
478
479 n_hdlc_send_frames (n_hdlc, tty);
480
481} /* end of n_hdlc_tty_wakeup() */
482
483/**
Linus Torvalds1da177e2005-04-16 15:20:36 -0700484 * 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 == 0 || 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/**
Matt Mackall4a4efbd2006-01-03 13:27:11 +0100552 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700553 * @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;
565 struct n_hdlc_buf *rbuf;
566
567 if (debuglevel >= DEBUG_LEVEL_INFO)
568 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
569
570 /* Validate the pointers */
571 if (!n_hdlc)
572 return -EIO;
573
574 /* verify user access to buffer */
575 if (!access_ok(VERIFY_WRITE, buf, nr)) {
576 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
577 "buffer\n", __FILE__, __LINE__);
578 return -EFAULT;
579 }
580
581 for (;;) {
582 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
583 return -EIO;
584
585 n_hdlc = tty2n_hdlc (tty);
586 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
587 tty != n_hdlc->tty)
588 return 0;
589
590 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
591 if (rbuf)
592 break;
593
594 /* no data */
595 if (file->f_flags & O_NONBLOCK)
596 return -EAGAIN;
597
598 interruptible_sleep_on (&tty->read_wait);
599 if (signal_pending(current))
600 return -EINTR;
601 }
602
603 if (rbuf->count > nr)
604 /* frame too large for caller's buffer (discard frame) */
605 ret = -EOVERFLOW;
606 else {
607 /* Copy the data to the caller's buffer */
608 if (copy_to_user(buf, rbuf->buf, rbuf->count))
609 ret = -EFAULT;
610 else
611 ret = rbuf->count;
612 }
613
614 /* return HDLC buffer to free list unless the free list */
615 /* count has exceeded the default value, in which case the */
616 /* buffer is freed back to the OS to conserve memory */
617 if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
618 kfree(rbuf);
619 else
620 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
621
622 return ret;
623
624} /* end of n_hdlc_tty_read() */
625
626/**
627 * n_hdlc_tty_write - write a single frame of data to device
628 * @tty - pointer to associated tty device instance data
629 * @file - pointer to file object data
630 * @data - pointer to transmit data (one frame)
631 * @count - size of transmit frame in bytes
632 *
633 * Returns the number of bytes written (or error code).
634 */
635static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
636 const unsigned char *data, size_t count)
637{
638 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
639 int error = 0;
640 DECLARE_WAITQUEUE(wait, current);
641 struct n_hdlc_buf *tbuf;
642
643 if (debuglevel >= DEBUG_LEVEL_INFO)
644 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
645 __FILE__,__LINE__,count);
646
647 /* Verify pointers */
648 if (!n_hdlc)
649 return -EIO;
650
651 if (n_hdlc->magic != HDLC_MAGIC)
652 return -EIO;
653
654 /* verify frame size */
655 if (count > maxframe ) {
656 if (debuglevel & DEBUG_LEVEL_INFO)
657 printk (KERN_WARNING
658 "n_hdlc_tty_write: truncating user packet "
659 "from %lu to %d\n", (unsigned long) count,
660 maxframe );
661 count = maxframe;
662 }
663
664 add_wait_queue(&tty->write_wait, &wait);
665 set_current_state(TASK_INTERRUPTIBLE);
666
667 /* Allocate transmit buffer */
668 /* sleep until transmit buffer available */
669 while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
670 schedule();
671
672 n_hdlc = tty2n_hdlc (tty);
673 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
674 tty != n_hdlc->tty) {
675 printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
676 error = -EIO;
677 break;
678 }
679
680 if (signal_pending(current)) {
681 error = -EINTR;
682 break;
683 }
684 }
685
686 set_current_state(TASK_RUNNING);
687 remove_wait_queue(&tty->write_wait, &wait);
688
689 if (!error) {
690 /* Retrieve the user's buffer */
691 memcpy(tbuf->buf, data, count);
692
693 /* Send the data */
694 tbuf->count = error = count;
695 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
696 n_hdlc_send_frames(n_hdlc,tty);
697 }
698
699 return error;
700
701} /* end of n_hdlc_tty_write() */
702
703/**
704 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
705 * @tty - pointer to tty instance data
706 * @file - pointer to open file object for device
707 * @cmd - IOCTL command code
708 * @arg - argument for IOCTL call (cmd dependent)
709 *
710 * Returns command dependent result.
711 */
712static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
713 unsigned int cmd, unsigned long arg)
714{
715 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
716 int error = 0;
717 int count;
718 unsigned long flags;
719
720 if (debuglevel >= DEBUG_LEVEL_INFO)
721 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
722 __FILE__,__LINE__,cmd);
723
724 /* Verify the status of the device */
725 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
726 return -EBADF;
727
728 switch (cmd) {
729 case FIONREAD:
730 /* report count of read data available */
731 /* in next available frame (if any) */
732 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
733 if (n_hdlc->rx_buf_list.head)
734 count = n_hdlc->rx_buf_list.head->count;
735 else
736 count = 0;
737 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
738 error = put_user(count, (int __user *)arg);
739 break;
740
741 case TIOCOUTQ:
742 /* get the pending tx byte count in the driver */
743 count = tty->driver->chars_in_buffer ?
744 tty->driver->chars_in_buffer(tty) : 0;
745 /* add size of next output frame in queue */
746 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
747 if (n_hdlc->tx_buf_list.head)
748 count += n_hdlc->tx_buf_list.head->count;
749 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
750 error = put_user(count, (int __user *)arg);
751 break;
752
753 default:
754 error = n_tty_ioctl (tty, file, cmd, arg);
755 break;
756 }
757 return error;
758
759} /* end of n_hdlc_tty_ioctl() */
760
761/**
762 * n_hdlc_tty_poll - TTY callback for poll system call
763 * @tty - pointer to tty instance data
764 * @filp - pointer to open file object for device
765 * @poll_table - wait queue for operations
766 *
767 * Determine which operations (read/write) will not block and return info
768 * to caller.
769 * Returns a bit mask containing info on which ops will not block.
770 */
771static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
772 poll_table *wait)
773{
774 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
775 unsigned int mask = 0;
776
777 if (debuglevel >= DEBUG_LEVEL_INFO)
778 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
779
780 if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
781 /* queue current process into any wait queue that */
782 /* may awaken in the future (read and write) */
783
784 poll_wait(filp, &tty->read_wait, wait);
785 poll_wait(filp, &tty->write_wait, wait);
786
787 /* set bits for operations that won't block */
Alan Cox9c1729d2007-07-15 23:39:43 -0700788 if (n_hdlc->rx_buf_list.head)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700789 mask |= POLLIN | POLLRDNORM; /* readable */
790 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
791 mask |= POLLHUP;
Alan Cox9c1729d2007-07-15 23:39:43 -0700792 if (tty_hung_up_p(filp))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700793 mask |= POLLHUP;
Alan Cox9c1729d2007-07-15 23:39:43 -0700794 if (!tty_is_writelocked(tty) &&
795 n_hdlc->tx_free_buf_list.head)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700796 mask |= POLLOUT | POLLWRNORM; /* writable */
797 }
798 return mask;
799} /* end of n_hdlc_tty_poll() */
800
801/**
802 * n_hdlc_alloc - allocate an n_hdlc instance data structure
803 *
804 * Returns a pointer to newly created structure if success, otherwise %NULL
805 */
806static struct n_hdlc *n_hdlc_alloc(void)
807{
808 struct n_hdlc_buf *buf;
809 int i;
810 struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
811
812 if (!n_hdlc)
813 return NULL;
814
815 memset(n_hdlc, 0, sizeof(*n_hdlc));
816
817 n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
818 n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
819 n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
820 n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
821
822 /* allocate free rx buffer list */
823 for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
824 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
825 if (buf)
826 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
827 else if (debuglevel >= DEBUG_LEVEL_INFO)
828 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
829 }
830
831 /* allocate free tx buffer list */
832 for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
833 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
834 if (buf)
835 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
836 else if (debuglevel >= DEBUG_LEVEL_INFO)
837 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
838 }
839
840 /* Initialize the control block */
841 n_hdlc->magic = HDLC_MAGIC;
842 n_hdlc->flags = 0;
843
844 return n_hdlc;
845
846} /* end of n_hdlc_alloc() */
847
848/**
849 * n_hdlc_buf_list_init - initialize specified HDLC buffer list
850 * @list - pointer to buffer list
851 */
852static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
853{
854 memset(list, 0, sizeof(*list));
855 spin_lock_init(&list->spinlock);
856} /* end of n_hdlc_buf_list_init() */
857
858/**
859 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
860 * @list - pointer to buffer list
861 * @buf - pointer to buffer
862 */
863static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
864 struct n_hdlc_buf *buf)
865{
866 unsigned long flags;
867 spin_lock_irqsave(&list->spinlock,flags);
868
869 buf->link=NULL;
Alan Cox9c1729d2007-07-15 23:39:43 -0700870 if (list->tail)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700871 list->tail->link = buf;
872 else
873 list->head = buf;
874 list->tail = buf;
875 (list->count)++;
876
877 spin_unlock_irqrestore(&list->spinlock,flags);
878
879} /* end of n_hdlc_buf_put() */
880
881/**
882 * n_hdlc_buf_get - remove and return an HDLC buffer from list
883 * @list - pointer to HDLC buffer list
884 *
885 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
886 * list.
887 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
888 */
889static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
890{
891 unsigned long flags;
892 struct n_hdlc_buf *buf;
893 spin_lock_irqsave(&list->spinlock,flags);
894
895 buf = list->head;
896 if (buf) {
897 list->head = buf->link;
898 (list->count)--;
899 }
900 if (!list->head)
901 list->tail = NULL;
902
903 spin_unlock_irqrestore(&list->spinlock,flags);
904 return buf;
905
906} /* end of n_hdlc_buf_get() */
907
908static char hdlc_banner[] __initdata =
909 KERN_INFO "HDLC line discipline: version " HDLC_VERSION
910 ", maxframe=%u\n";
911static char hdlc_register_ok[] __initdata =
912 KERN_INFO "N_HDLC line discipline registered.\n";
913static char hdlc_register_fail[] __initdata =
914 KERN_ERR "error registering line discipline: %d\n";
915static char hdlc_init_fail[] __initdata =
916 KERN_INFO "N_HDLC: init failure %d\n";
917
918static int __init n_hdlc_init(void)
919{
920 int status;
921
922 /* range check maxframe arg */
923 if (maxframe < 4096)
924 maxframe = 4096;
925 else if (maxframe > 65535)
926 maxframe = 65535;
927
928 printk(hdlc_banner, maxframe);
929
930 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
931 if (!status)
932 printk(hdlc_register_ok);
933 else
934 printk(hdlc_register_fail, status);
935
936 if (status)
937 printk(hdlc_init_fail, status);
938 return status;
939
940} /* end of init_module() */
941
942static char hdlc_unregister_ok[] __exitdata =
943 KERN_INFO "N_HDLC: line discipline unregistered\n";
944static char hdlc_unregister_fail[] __exitdata =
945 KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
946
947static void __exit n_hdlc_exit(void)
948{
949 /* Release tty registration of line discipline */
Alexey Dobriyan64ccd712005-06-23 00:10:33 -0700950 int status = tty_unregister_ldisc(N_HDLC);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700951
952 if (status)
953 printk(hdlc_unregister_fail, status);
954 else
955 printk(hdlc_unregister_ok);
956}
957
958module_init(n_hdlc_init);
959module_exit(n_hdlc_exit);
960
961MODULE_LICENSE("GPL");
962MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
963module_param(debuglevel, int, 0);
964module_param(maxframe, int, 0);
965MODULE_ALIAS_LDISC(N_HDLC);