blob: 5079beda69b5af142af8e9bfaa4ffd62c635c881 [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
84#include <linux/config.h>
85#include <linux/module.h>
86#include <linux/init.h>
87#include <linux/kernel.h>
88#include <linux/sched.h>
89#include <linux/types.h>
90#include <linux/fcntl.h>
91#include <linux/interrupt.h>
92#include <linux/ptrace.h>
93
94#undef VERSION
95#define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
96
97#include <linux/poll.h>
98#include <linux/in.h>
99#include <linux/ioctl.h>
100#include <linux/slab.h>
101#include <linux/tty.h>
102#include <linux/errno.h>
103#include <linux/string.h> /* used in new tty drivers */
104#include <linux/signal.h> /* used in new tty drivers */
105#include <linux/if.h>
106#include <linux/bitops.h>
107
108#include <asm/system.h>
109#include <asm/termios.h>
110#include <asm/uaccess.h>
111
112/*
113 * Buffers for individual HDLC frames
114 */
115#define MAX_HDLC_FRAME_SIZE 65535
116#define DEFAULT_RX_BUF_COUNT 10
117#define MAX_RX_BUF_COUNT 60
118#define DEFAULT_TX_BUF_COUNT 1
119
120struct n_hdlc_buf {
121 struct n_hdlc_buf *link;
122 int count;
123 char buf[1];
124};
125
126#define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
127
128struct n_hdlc_buf_list {
129 struct n_hdlc_buf *head;
130 struct n_hdlc_buf *tail;
131 int count;
132 spinlock_t spinlock;
133};
134
135/**
136 * struct n_hdlc - per device instance data structure
137 * @magic - magic value for structure
138 * @flags - miscellaneous control flags
139 * @tty - ptr to TTY structure
140 * @backup_tty - TTY to use if tty gets closed
141 * @tbusy - reentrancy flag for tx wakeup code
142 * @woke_up - FIXME: describe this field
143 * @tbuf - currently transmitting tx buffer
144 * @tx_buf_list - list of pending transmit frame buffers
145 * @rx_buf_list - list of received frame buffers
146 * @tx_free_buf_list - list unused transmit frame buffers
147 * @rx_free_buf_list - list unused received frame buffers
148 */
149struct n_hdlc {
150 int magic;
151 __u32 flags;
152 struct tty_struct *tty;
153 struct tty_struct *backup_tty;
154 int tbusy;
155 int woke_up;
156 struct n_hdlc_buf *tbuf;
157 struct n_hdlc_buf_list tx_buf_list;
158 struct n_hdlc_buf_list rx_buf_list;
159 struct n_hdlc_buf_list tx_free_buf_list;
160 struct n_hdlc_buf_list rx_free_buf_list;
161};
162
163/*
164 * HDLC buffer list manipulation functions
165 */
166static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list);
167static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
168 struct n_hdlc_buf *buf);
169static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
170
171/* Local functions */
172
173static struct n_hdlc *n_hdlc_alloc (void);
174
175/* debug level can be set by insmod for debugging purposes */
176#define DEBUG_LEVEL_INFO 1
177static int debuglevel;
178
179/* max frame size for memory allocations */
180static int maxframe = 4096;
181
182/* TTY callbacks */
183
184static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
185 __u8 __user *buf, size_t nr);
186static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
187 const unsigned char *buf, size_t nr);
188static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
189 unsigned int cmd, unsigned long arg);
190static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
191 poll_table *wait);
192static int n_hdlc_tty_open(struct tty_struct *tty);
193static void n_hdlc_tty_close(struct tty_struct *tty);
194static int n_hdlc_tty_room(struct tty_struct *tty);
195static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
196 char *fp, int count);
197static void n_hdlc_tty_wakeup(struct tty_struct *tty);
198
199#define bset(p,b) ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
200
201#define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
202#define n_hdlc2tty(n_hdlc) ((n_hdlc)->tty)
203
204static struct tty_ldisc n_hdlc_ldisc = {
205 .owner = THIS_MODULE,
206 .magic = TTY_LDISC_MAGIC,
207 .name = "hdlc",
208 .open = n_hdlc_tty_open,
209 .close = n_hdlc_tty_close,
210 .read = n_hdlc_tty_read,
211 .write = n_hdlc_tty_write,
212 .ioctl = n_hdlc_tty_ioctl,
213 .poll = n_hdlc_tty_poll,
214 .receive_buf = n_hdlc_tty_receive,
215 .receive_room = n_hdlc_tty_room,
216 .write_wakeup = n_hdlc_tty_wakeup,
217};
218
219/**
220 * n_hdlc_release - release an n_hdlc per device line discipline info structure
221 * @n_hdlc - per device line discipline info structure
222 */
223static void n_hdlc_release(struct n_hdlc *n_hdlc)
224{
225 struct tty_struct *tty = n_hdlc2tty (n_hdlc);
226 struct n_hdlc_buf *buf;
227
228 if (debuglevel >= DEBUG_LEVEL_INFO)
229 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
230
231 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
232 wake_up_interruptible (&tty->read_wait);
233 wake_up_interruptible (&tty->write_wait);
234
235 if (tty != NULL && tty->disc_data == n_hdlc)
236 tty->disc_data = NULL; /* Break the tty->n_hdlc link */
237
238 /* Release transmit and receive buffers */
239 for(;;) {
240 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
241 if (buf) {
242 kfree(buf);
243 } else
244 break;
245 }
246 for(;;) {
247 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
248 if (buf) {
249 kfree(buf);
250 } else
251 break;
252 }
253 for(;;) {
254 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
255 if (buf) {
256 kfree(buf);
257 } else
258 break;
259 }
260 for(;;) {
261 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
262 if (buf) {
263 kfree(buf);
264 } else
265 break;
266 }
267 if (n_hdlc->tbuf)
268 kfree(n_hdlc->tbuf);
269 kfree(n_hdlc);
270
271} /* end of n_hdlc_release() */
272
273/**
274 * n_hdlc_tty_close - line discipline close
275 * @tty - pointer to tty info structure
276 *
277 * Called when the line discipline is changed to something
278 * else, the tty is closed, or the tty detects a hangup.
279 */
280static void n_hdlc_tty_close(struct tty_struct *tty)
281{
282 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
283
284 if (debuglevel >= DEBUG_LEVEL_INFO)
285 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
286
287 if (n_hdlc != NULL) {
288 if (n_hdlc->magic != HDLC_MAGIC) {
289 printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
290 return;
291 }
292#if defined(TTY_NO_WRITE_SPLIT)
293 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
294#endif
295 tty->disc_data = NULL;
296 if (tty == n_hdlc->backup_tty)
297 n_hdlc->backup_tty = NULL;
298 if (tty != n_hdlc->tty)
299 return;
300 if (n_hdlc->backup_tty) {
301 n_hdlc->tty = n_hdlc->backup_tty;
302 } else {
303 n_hdlc_release (n_hdlc);
304 }
305 }
306
307 if (debuglevel >= DEBUG_LEVEL_INFO)
308 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
309
310} /* end of n_hdlc_tty_close() */
311
312/**
313 * n_hdlc_tty_open - called when line discipline changed to n_hdlc
314 * @tty - pointer to tty info structure
315 *
316 * Returns 0 if success, otherwise error code
317 */
318static int n_hdlc_tty_open (struct tty_struct *tty)
319{
320 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
321
322 if (debuglevel >= DEBUG_LEVEL_INFO)
323 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
324 __FILE__,__LINE__,
325 tty->name);
326
327 /* There should not be an existing table for this slot. */
328 if (n_hdlc) {
329 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
330 return -EEXIST;
331 }
332
333 n_hdlc = n_hdlc_alloc();
334 if (!n_hdlc) {
335 printk (KERN_ERR "n_hdlc_alloc failed\n");
336 return -ENFILE;
337 }
338
339 tty->disc_data = n_hdlc;
340 n_hdlc->tty = tty;
341
342#if defined(TTY_NO_WRITE_SPLIT)
343 /* change tty_io write() to not split large writes into 8K chunks */
344 set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
345#endif
346
347 /* Flush any pending characters in the driver and discipline. */
348
349 if (tty->ldisc.flush_buffer)
350 tty->ldisc.flush_buffer (tty);
351
352 if (tty->driver->flush_buffer)
353 tty->driver->flush_buffer (tty);
354
355 if (debuglevel >= DEBUG_LEVEL_INFO)
356 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
357
358 return 0;
359
360} /* end of n_tty_hdlc_open() */
361
362/**
363 * n_hdlc_send_frames - send frames on pending send buffer list
364 * @n_hdlc - pointer to ldisc instance data
365 * @tty - pointer to tty instance data
366 *
367 * Send frames on pending send buffer list until the driver does not accept a
368 * frame (busy) this function is called after adding a frame to the send buffer
369 * list and by the tty wakeup callback.
370 */
371static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
372{
373 register int actual;
374 unsigned long flags;
375 struct n_hdlc_buf *tbuf;
376
377 if (debuglevel >= DEBUG_LEVEL_INFO)
378 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
379 check_again:
380
381 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
382 if (n_hdlc->tbusy) {
383 n_hdlc->woke_up = 1;
384 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
385 return;
386 }
387 n_hdlc->tbusy = 1;
388 n_hdlc->woke_up = 0;
389 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
390
391 /* get current transmit buffer or get new transmit */
392 /* buffer from list of pending transmit buffers */
393
394 tbuf = n_hdlc->tbuf;
395 if (!tbuf)
396 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
397
398 while (tbuf) {
399 if (debuglevel >= DEBUG_LEVEL_INFO)
400 printk("%s(%d)sending frame %p, count=%d\n",
401 __FILE__,__LINE__,tbuf,tbuf->count);
402
403 /* Send the next block of data to device */
404 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
405 actual = tty->driver->write(tty, tbuf->buf, tbuf->count);
406
407 /* if transmit error, throw frame away by */
408 /* pretending it was accepted by driver */
409 if (actual < 0)
410 actual = tbuf->count;
411
412 if (actual == tbuf->count) {
413 if (debuglevel >= DEBUG_LEVEL_INFO)
414 printk("%s(%d)frame %p completed\n",
415 __FILE__,__LINE__,tbuf);
416
417 /* free current transmit buffer */
418 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
419
420 /* this tx buffer is done */
421 n_hdlc->tbuf = NULL;
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 /* buffer not accepted by driver */
434 /* set this buffer as pending buffer */
435 n_hdlc->tbuf = tbuf;
436 break;
437 }
438 }
439
440 if (!tbuf)
441 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
442
443 /* Clear the re-entry flag */
444 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
445 n_hdlc->tbusy = 0;
446 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
447
448 if (n_hdlc->woke_up)
449 goto check_again;
450
451 if (debuglevel >= DEBUG_LEVEL_INFO)
452 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
453
454} /* end of n_hdlc_send_frames() */
455
456/**
457 * n_hdlc_tty_wakeup - Callback for transmit wakeup
458 * @tty - pointer to associated tty instance data
459 *
460 * Called when low level device driver can accept more send data.
461 */
462static void n_hdlc_tty_wakeup(struct tty_struct *tty)
463{
464 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
465
466 if (debuglevel >= DEBUG_LEVEL_INFO)
467 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
468
469 if (!n_hdlc)
470 return;
471
472 if (tty != n_hdlc->tty) {
473 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
474 return;
475 }
476
477 n_hdlc_send_frames (n_hdlc, tty);
478
479} /* end of n_hdlc_tty_wakeup() */
480
481/**
482 * n_hdlc_tty_room - Return the amount of space left in the receiver's buffer
483 * @tty - pointer to associated tty instance data
484 *
485 * Callback function from tty driver. Return the amount of space left in the
486 * receiver's buffer to decide if remote transmitter is to be throttled.
487 */
488static int n_hdlc_tty_room(struct tty_struct *tty)
489{
490 if (debuglevel >= DEBUG_LEVEL_INFO)
491 printk("%s(%d)n_hdlc_tty_room() called\n",__FILE__,__LINE__);
492 /* always return a larger number to prevent */
493 /* throttling of remote transmitter. */
494 return 65536;
495} /* end of n_hdlc_tty_root() */
496
497/**
498 * n_hdlc_tty_receive - Called by tty driver when receive data is available
499 * @tty - pointer to tty instance data
500 * @data - pointer to received data
501 * @flags - pointer to flags for data
502 * @count - count of received data in bytes
503 *
504 * Called by tty low level driver when receive data is available. Data is
505 * interpreted as one HDLC frame.
506 */
507static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
508 char *flags, int count)
509{
510 register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
511 register struct n_hdlc_buf *buf;
512
513 if (debuglevel >= DEBUG_LEVEL_INFO)
514 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
515 __FILE__,__LINE__, count);
516
517 /* This can happen if stuff comes in on the backup tty */
518 if (n_hdlc == 0 || tty != n_hdlc->tty)
519 return;
520
521 /* verify line is using HDLC discipline */
522 if (n_hdlc->magic != HDLC_MAGIC) {
523 printk("%s(%d) line not using HDLC discipline\n",
524 __FILE__,__LINE__);
525 return;
526 }
527
528 if ( count>maxframe ) {
529 if (debuglevel >= DEBUG_LEVEL_INFO)
530 printk("%s(%d) rx count>maxframesize, data discarded\n",
531 __FILE__,__LINE__);
532 return;
533 }
534
535 /* get a free HDLC buffer */
536 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
537 if (!buf) {
538 /* no buffers in free list, attempt to allocate another rx buffer */
539 /* unless the maximum count has been reached */
540 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
541 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
542 }
543
544 if (!buf) {
545 if (debuglevel >= DEBUG_LEVEL_INFO)
546 printk("%s(%d) no more rx buffers, data discarded\n",
547 __FILE__,__LINE__);
548 return;
549 }
550
551 /* copy received data to HDLC buffer */
552 memcpy(buf->buf,data,count);
553 buf->count=count;
554
555 /* add HDLC buffer to list of received frames */
556 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
557
558 /* wake up any blocked reads and perform async signalling */
559 wake_up_interruptible (&tty->read_wait);
560 if (n_hdlc->tty->fasync != NULL)
561 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
562
563} /* end of n_hdlc_tty_receive() */
564
565/**
566 * n_hdlc_tty_read - Called to retreive one frame of data (if available)
567 * @tty - pointer to tty instance data
568 * @file - pointer to open file object
569 * @buf - pointer to returned data buffer
570 * @nr - size of returned data buffer
571 *
572 * Returns the number of bytes returned or error code.
573 */
574static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
575 __u8 __user *buf, size_t nr)
576{
577 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
578 int ret;
579 struct n_hdlc_buf *rbuf;
580
581 if (debuglevel >= DEBUG_LEVEL_INFO)
582 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
583
584 /* Validate the pointers */
585 if (!n_hdlc)
586 return -EIO;
587
588 /* verify user access to buffer */
589 if (!access_ok(VERIFY_WRITE, buf, nr)) {
590 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
591 "buffer\n", __FILE__, __LINE__);
592 return -EFAULT;
593 }
594
595 for (;;) {
596 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
597 return -EIO;
598
599 n_hdlc = tty2n_hdlc (tty);
600 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
601 tty != n_hdlc->tty)
602 return 0;
603
604 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
605 if (rbuf)
606 break;
607
608 /* no data */
609 if (file->f_flags & O_NONBLOCK)
610 return -EAGAIN;
611
612 interruptible_sleep_on (&tty->read_wait);
613 if (signal_pending(current))
614 return -EINTR;
615 }
616
617 if (rbuf->count > nr)
618 /* frame too large for caller's buffer (discard frame) */
619 ret = -EOVERFLOW;
620 else {
621 /* Copy the data to the caller's buffer */
622 if (copy_to_user(buf, rbuf->buf, rbuf->count))
623 ret = -EFAULT;
624 else
625 ret = rbuf->count;
626 }
627
628 /* return HDLC buffer to free list unless the free list */
629 /* count has exceeded the default value, in which case the */
630 /* buffer is freed back to the OS to conserve memory */
631 if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
632 kfree(rbuf);
633 else
634 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
635
636 return ret;
637
638} /* end of n_hdlc_tty_read() */
639
640/**
641 * n_hdlc_tty_write - write a single frame of data to device
642 * @tty - pointer to associated tty device instance data
643 * @file - pointer to file object data
644 * @data - pointer to transmit data (one frame)
645 * @count - size of transmit frame in bytes
646 *
647 * Returns the number of bytes written (or error code).
648 */
649static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
650 const unsigned char *data, size_t count)
651{
652 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
653 int error = 0;
654 DECLARE_WAITQUEUE(wait, current);
655 struct n_hdlc_buf *tbuf;
656
657 if (debuglevel >= DEBUG_LEVEL_INFO)
658 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
659 __FILE__,__LINE__,count);
660
661 /* Verify pointers */
662 if (!n_hdlc)
663 return -EIO;
664
665 if (n_hdlc->magic != HDLC_MAGIC)
666 return -EIO;
667
668 /* verify frame size */
669 if (count > maxframe ) {
670 if (debuglevel & DEBUG_LEVEL_INFO)
671 printk (KERN_WARNING
672 "n_hdlc_tty_write: truncating user packet "
673 "from %lu to %d\n", (unsigned long) count,
674 maxframe );
675 count = maxframe;
676 }
677
678 add_wait_queue(&tty->write_wait, &wait);
679 set_current_state(TASK_INTERRUPTIBLE);
680
681 /* Allocate transmit buffer */
682 /* sleep until transmit buffer available */
683 while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
684 schedule();
685
686 n_hdlc = tty2n_hdlc (tty);
687 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
688 tty != n_hdlc->tty) {
689 printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
690 error = -EIO;
691 break;
692 }
693
694 if (signal_pending(current)) {
695 error = -EINTR;
696 break;
697 }
698 }
699
700 set_current_state(TASK_RUNNING);
701 remove_wait_queue(&tty->write_wait, &wait);
702
703 if (!error) {
704 /* Retrieve the user's buffer */
705 memcpy(tbuf->buf, data, count);
706
707 /* Send the data */
708 tbuf->count = error = count;
709 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
710 n_hdlc_send_frames(n_hdlc,tty);
711 }
712
713 return error;
714
715} /* end of n_hdlc_tty_write() */
716
717/**
718 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
719 * @tty - pointer to tty instance data
720 * @file - pointer to open file object for device
721 * @cmd - IOCTL command code
722 * @arg - argument for IOCTL call (cmd dependent)
723 *
724 * Returns command dependent result.
725 */
726static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
727 unsigned int cmd, unsigned long arg)
728{
729 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
730 int error = 0;
731 int count;
732 unsigned long flags;
733
734 if (debuglevel >= DEBUG_LEVEL_INFO)
735 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
736 __FILE__,__LINE__,cmd);
737
738 /* Verify the status of the device */
739 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
740 return -EBADF;
741
742 switch (cmd) {
743 case FIONREAD:
744 /* report count of read data available */
745 /* in next available frame (if any) */
746 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
747 if (n_hdlc->rx_buf_list.head)
748 count = n_hdlc->rx_buf_list.head->count;
749 else
750 count = 0;
751 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
752 error = put_user(count, (int __user *)arg);
753 break;
754
755 case TIOCOUTQ:
756 /* get the pending tx byte count in the driver */
757 count = tty->driver->chars_in_buffer ?
758 tty->driver->chars_in_buffer(tty) : 0;
759 /* add size of next output frame in queue */
760 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
761 if (n_hdlc->tx_buf_list.head)
762 count += n_hdlc->tx_buf_list.head->count;
763 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
764 error = put_user(count, (int __user *)arg);
765 break;
766
767 default:
768 error = n_tty_ioctl (tty, file, cmd, arg);
769 break;
770 }
771 return error;
772
773} /* end of n_hdlc_tty_ioctl() */
774
775/**
776 * n_hdlc_tty_poll - TTY callback for poll system call
777 * @tty - pointer to tty instance data
778 * @filp - pointer to open file object for device
779 * @poll_table - wait queue for operations
780 *
781 * Determine which operations (read/write) will not block and return info
782 * to caller.
783 * Returns a bit mask containing info on which ops will not block.
784 */
785static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
786 poll_table *wait)
787{
788 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
789 unsigned int mask = 0;
790
791 if (debuglevel >= DEBUG_LEVEL_INFO)
792 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
793
794 if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
795 /* queue current process into any wait queue that */
796 /* may awaken in the future (read and write) */
797
798 poll_wait(filp, &tty->read_wait, wait);
799 poll_wait(filp, &tty->write_wait, wait);
800
801 /* set bits for operations that won't block */
802 if(n_hdlc->rx_buf_list.head)
803 mask |= POLLIN | POLLRDNORM; /* readable */
804 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
805 mask |= POLLHUP;
806 if(tty_hung_up_p(filp))
807 mask |= POLLHUP;
808 if(n_hdlc->tx_free_buf_list.head)
809 mask |= POLLOUT | POLLWRNORM; /* writable */
810 }
811 return mask;
812} /* end of n_hdlc_tty_poll() */
813
814/**
815 * n_hdlc_alloc - allocate an n_hdlc instance data structure
816 *
817 * Returns a pointer to newly created structure if success, otherwise %NULL
818 */
819static struct n_hdlc *n_hdlc_alloc(void)
820{
821 struct n_hdlc_buf *buf;
822 int i;
823 struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
824
825 if (!n_hdlc)
826 return NULL;
827
828 memset(n_hdlc, 0, sizeof(*n_hdlc));
829
830 n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
831 n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
832 n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
833 n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
834
835 /* allocate free rx buffer list */
836 for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
837 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
838 if (buf)
839 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
840 else if (debuglevel >= DEBUG_LEVEL_INFO)
841 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
842 }
843
844 /* allocate free tx buffer list */
845 for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
846 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
847 if (buf)
848 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
849 else if (debuglevel >= DEBUG_LEVEL_INFO)
850 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
851 }
852
853 /* Initialize the control block */
854 n_hdlc->magic = HDLC_MAGIC;
855 n_hdlc->flags = 0;
856
857 return n_hdlc;
858
859} /* end of n_hdlc_alloc() */
860
861/**
862 * n_hdlc_buf_list_init - initialize specified HDLC buffer list
863 * @list - pointer to buffer list
864 */
865static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
866{
867 memset(list, 0, sizeof(*list));
868 spin_lock_init(&list->spinlock);
869} /* end of n_hdlc_buf_list_init() */
870
871/**
872 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
873 * @list - pointer to buffer list
874 * @buf - pointer to buffer
875 */
876static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
877 struct n_hdlc_buf *buf)
878{
879 unsigned long flags;
880 spin_lock_irqsave(&list->spinlock,flags);
881
882 buf->link=NULL;
883 if(list->tail)
884 list->tail->link = buf;
885 else
886 list->head = buf;
887 list->tail = buf;
888 (list->count)++;
889
890 spin_unlock_irqrestore(&list->spinlock,flags);
891
892} /* end of n_hdlc_buf_put() */
893
894/**
895 * n_hdlc_buf_get - remove and return an HDLC buffer from list
896 * @list - pointer to HDLC buffer list
897 *
898 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
899 * list.
900 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
901 */
902static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
903{
904 unsigned long flags;
905 struct n_hdlc_buf *buf;
906 spin_lock_irqsave(&list->spinlock,flags);
907
908 buf = list->head;
909 if (buf) {
910 list->head = buf->link;
911 (list->count)--;
912 }
913 if (!list->head)
914 list->tail = NULL;
915
916 spin_unlock_irqrestore(&list->spinlock,flags);
917 return buf;
918
919} /* end of n_hdlc_buf_get() */
920
921static char hdlc_banner[] __initdata =
922 KERN_INFO "HDLC line discipline: version " HDLC_VERSION
923 ", maxframe=%u\n";
924static char hdlc_register_ok[] __initdata =
925 KERN_INFO "N_HDLC line discipline registered.\n";
926static char hdlc_register_fail[] __initdata =
927 KERN_ERR "error registering line discipline: %d\n";
928static char hdlc_init_fail[] __initdata =
929 KERN_INFO "N_HDLC: init failure %d\n";
930
931static int __init n_hdlc_init(void)
932{
933 int status;
934
935 /* range check maxframe arg */
936 if (maxframe < 4096)
937 maxframe = 4096;
938 else if (maxframe > 65535)
939 maxframe = 65535;
940
941 printk(hdlc_banner, maxframe);
942
943 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
944 if (!status)
945 printk(hdlc_register_ok);
946 else
947 printk(hdlc_register_fail, status);
948
949 if (status)
950 printk(hdlc_init_fail, status);
951 return status;
952
953} /* end of init_module() */
954
955static char hdlc_unregister_ok[] __exitdata =
956 KERN_INFO "N_HDLC: line discipline unregistered\n";
957static char hdlc_unregister_fail[] __exitdata =
958 KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
959
960static void __exit n_hdlc_exit(void)
961{
962 /* Release tty registration of line discipline */
Alexey Dobriyan64ccd712005-06-23 00:10:33 -0700963 int status = tty_unregister_ldisc(N_HDLC);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700964
965 if (status)
966 printk(hdlc_unregister_fail, status);
967 else
968 printk(hdlc_unregister_ok);
969}
970
971module_init(n_hdlc_init);
972module_exit(n_hdlc_exit);
973
974MODULE_LICENSE("GPL");
975MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
976module_param(debuglevel, int, 0);
977module_param(maxframe, int, 0);
978MODULE_ALIAS_LDISC(N_HDLC);