blob: 69ec6399c714b206ea11de8c30d8ba75fd0a9bd6 [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
Alan Coxa352def2008-07-16 21:53:12 +0100202static struct tty_ldisc_ops n_hdlc_ldisc = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700203 .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. */
Alan Coxa352def2008-07-16 21:53:12 +0100345 if (tty->ldisc.ops->flush_buffer)
346 tty->ldisc.ops->flush_buffer(tty);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347
Alan Coxf34d7a52008-04-30 00:54:13 -0700348 tty_driver_flush_buffer(tty);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349
350 if (debuglevel >= DEBUG_LEVEL_INFO)
351 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
352
353 return 0;
354
355} /* end of n_tty_hdlc_open() */
356
357/**
358 * n_hdlc_send_frames - send frames on pending send buffer list
359 * @n_hdlc - pointer to ldisc instance data
360 * @tty - pointer to tty instance data
361 *
362 * Send frames on pending send buffer list until the driver does not accept a
363 * frame (busy) this function is called after adding a frame to the send buffer
364 * list and by the tty wakeup callback.
365 */
366static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
367{
368 register int actual;
369 unsigned long flags;
370 struct n_hdlc_buf *tbuf;
371
372 if (debuglevel >= DEBUG_LEVEL_INFO)
373 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
374 check_again:
375
376 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
377 if (n_hdlc->tbusy) {
378 n_hdlc->woke_up = 1;
379 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
380 return;
381 }
382 n_hdlc->tbusy = 1;
383 n_hdlc->woke_up = 0;
384 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
385
386 /* get current transmit buffer or get new transmit */
387 /* buffer from list of pending transmit buffers */
388
389 tbuf = n_hdlc->tbuf;
390 if (!tbuf)
391 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
392
393 while (tbuf) {
394 if (debuglevel >= DEBUG_LEVEL_INFO)
395 printk("%s(%d)sending frame %p, count=%d\n",
396 __FILE__,__LINE__,tbuf,tbuf->count);
397
398 /* Send the next block of data to device */
399 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
Alan Coxf34d7a52008-04-30 00:54:13 -0700400 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
Jiri Slabyb0fed312007-07-15 23:40:12 -0700401
402 /* rollback was possible and has been done */
403 if (actual == -ERESTARTSYS) {
404 n_hdlc->tbuf = tbuf;
405 break;
406 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700407 /* 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/**
Linus Torvalds1da177e2005-04-16 15:20:36 -0700482 * n_hdlc_tty_receive - Called by tty driver when receive data is available
483 * @tty - pointer to tty instance data
484 * @data - pointer to received data
485 * @flags - pointer to flags for data
486 * @count - count of received data in bytes
487 *
488 * Called by tty low level driver when receive data is available. Data is
489 * interpreted as one HDLC frame.
490 */
491static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
492 char *flags, int count)
493{
494 register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
495 register struct n_hdlc_buf *buf;
496
497 if (debuglevel >= DEBUG_LEVEL_INFO)
498 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
499 __FILE__,__LINE__, count);
500
501 /* This can happen if stuff comes in on the backup tty */
Harvey Harrisona01e0352008-04-28 16:50:04 -0700502 if (!n_hdlc || tty != n_hdlc->tty)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700503 return;
504
505 /* verify line is using HDLC discipline */
506 if (n_hdlc->magic != HDLC_MAGIC) {
507 printk("%s(%d) line not using HDLC discipline\n",
508 __FILE__,__LINE__);
509 return;
510 }
511
512 if ( count>maxframe ) {
513 if (debuglevel >= DEBUG_LEVEL_INFO)
514 printk("%s(%d) rx count>maxframesize, data discarded\n",
515 __FILE__,__LINE__);
516 return;
517 }
518
519 /* get a free HDLC buffer */
520 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
521 if (!buf) {
522 /* no buffers in free list, attempt to allocate another rx buffer */
523 /* unless the maximum count has been reached */
524 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
525 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
526 }
527
528 if (!buf) {
529 if (debuglevel >= DEBUG_LEVEL_INFO)
530 printk("%s(%d) no more rx buffers, data discarded\n",
531 __FILE__,__LINE__);
532 return;
533 }
534
535 /* copy received data to HDLC buffer */
536 memcpy(buf->buf,data,count);
537 buf->count=count;
538
539 /* add HDLC buffer to list of received frames */
540 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
541
542 /* wake up any blocked reads and perform async signalling */
543 wake_up_interruptible (&tty->read_wait);
544 if (n_hdlc->tty->fasync != NULL)
545 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
546
547} /* end of n_hdlc_tty_receive() */
548
549/**
Matt Mackall4a4efbd2006-01-03 13:27:11 +0100550 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700551 * @tty - pointer to tty instance data
552 * @file - pointer to open file object
553 * @buf - pointer to returned data buffer
554 * @nr - size of returned data buffer
555 *
556 * Returns the number of bytes returned or error code.
557 */
558static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
559 __u8 __user *buf, size_t nr)
560{
561 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
562 int ret;
563 struct n_hdlc_buf *rbuf;
564
565 if (debuglevel >= DEBUG_LEVEL_INFO)
566 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
567
568 /* Validate the pointers */
569 if (!n_hdlc)
570 return -EIO;
571
572 /* verify user access to buffer */
573 if (!access_ok(VERIFY_WRITE, buf, nr)) {
574 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
575 "buffer\n", __FILE__, __LINE__);
576 return -EFAULT;
577 }
578
Alan Cox04f378b2008-04-30 00:53:29 -0700579 lock_kernel();
580
Linus Torvalds1da177e2005-04-16 15:20:36 -0700581 for (;;) {
Alan Cox04f378b2008-04-30 00:53:29 -0700582 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
583 unlock_kernel();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700584 return -EIO;
Alan Cox04f378b2008-04-30 00:53:29 -0700585 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700586
587 n_hdlc = tty2n_hdlc (tty);
588 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
Alan Cox04f378b2008-04-30 00:53:29 -0700589 tty != n_hdlc->tty) {
590 unlock_kernel();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700591 return 0;
Alan Cox04f378b2008-04-30 00:53:29 -0700592 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593
594 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
595 if (rbuf)
596 break;
597
598 /* no data */
Alan Cox04f378b2008-04-30 00:53:29 -0700599 if (file->f_flags & O_NONBLOCK) {
600 unlock_kernel();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700601 return -EAGAIN;
Alan Cox04f378b2008-04-30 00:53:29 -0700602 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700603
604 interruptible_sleep_on (&tty->read_wait);
Alan Cox04f378b2008-04-30 00:53:29 -0700605 if (signal_pending(current)) {
606 unlock_kernel();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700607 return -EINTR;
Alan Cox04f378b2008-04-30 00:53:29 -0700608 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700609 }
610
611 if (rbuf->count > nr)
612 /* frame too large for caller's buffer (discard frame) */
613 ret = -EOVERFLOW;
614 else {
615 /* Copy the data to the caller's buffer */
616 if (copy_to_user(buf, rbuf->buf, rbuf->count))
617 ret = -EFAULT;
618 else
619 ret = rbuf->count;
620 }
621
622 /* return HDLC buffer to free list unless the free list */
623 /* count has exceeded the default value, in which case the */
624 /* buffer is freed back to the OS to conserve memory */
625 if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
626 kfree(rbuf);
627 else
628 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
Alan Cox04f378b2008-04-30 00:53:29 -0700629 unlock_kernel();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700630 return ret;
631
632} /* end of n_hdlc_tty_read() */
633
634/**
635 * n_hdlc_tty_write - write a single frame of data to device
636 * @tty - pointer to associated tty device instance data
637 * @file - pointer to file object data
638 * @data - pointer to transmit data (one frame)
639 * @count - size of transmit frame in bytes
640 *
641 * Returns the number of bytes written (or error code).
642 */
643static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
644 const unsigned char *data, size_t count)
645{
646 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
647 int error = 0;
648 DECLARE_WAITQUEUE(wait, current);
649 struct n_hdlc_buf *tbuf;
650
651 if (debuglevel >= DEBUG_LEVEL_INFO)
652 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
653 __FILE__,__LINE__,count);
654
655 /* Verify pointers */
656 if (!n_hdlc)
657 return -EIO;
658
659 if (n_hdlc->magic != HDLC_MAGIC)
660 return -EIO;
661
662 /* verify frame size */
663 if (count > maxframe ) {
664 if (debuglevel & DEBUG_LEVEL_INFO)
665 printk (KERN_WARNING
666 "n_hdlc_tty_write: truncating user packet "
667 "from %lu to %d\n", (unsigned long) count,
668 maxframe );
669 count = maxframe;
670 }
671
Alan Cox04f378b2008-04-30 00:53:29 -0700672 lock_kernel();
673
Linus Torvalds1da177e2005-04-16 15:20:36 -0700674 add_wait_queue(&tty->write_wait, &wait);
675 set_current_state(TASK_INTERRUPTIBLE);
676
677 /* Allocate transmit buffer */
678 /* sleep until transmit buffer available */
679 while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
Paul Fulghumc72f5272008-07-22 11:21:19 +0100680 if (file->f_flags & O_NONBLOCK) {
681 error = -EAGAIN;
682 break;
683 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700684 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 }
Alan Cox04f378b2008-04-30 00:53:29 -0700712 unlock_kernel();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700713 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 */
Alan Coxf34d7a52008-04-30 00:54:13 -0700757 count = tty_chars_in_buffer(tty);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700758 /* add size of next output frame in queue */
759 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
760 if (n_hdlc->tx_buf_list.head)
761 count += n_hdlc->tx_buf_list.head->count;
762 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
763 error = put_user(count, (int __user *)arg);
764 break;
765
766 default:
767 error = n_tty_ioctl (tty, file, cmd, arg);
768 break;
769 }
770 return error;
771
772} /* end of n_hdlc_tty_ioctl() */
773
774/**
775 * n_hdlc_tty_poll - TTY callback for poll system call
776 * @tty - pointer to tty instance data
777 * @filp - pointer to open file object for device
778 * @poll_table - wait queue for operations
779 *
780 * Determine which operations (read/write) will not block and return info
781 * to caller.
782 * Returns a bit mask containing info on which ops will not block.
783 */
784static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
785 poll_table *wait)
786{
787 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
788 unsigned int mask = 0;
789
790 if (debuglevel >= DEBUG_LEVEL_INFO)
791 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
792
793 if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
794 /* queue current process into any wait queue that */
795 /* may awaken in the future (read and write) */
796
797 poll_wait(filp, &tty->read_wait, wait);
798 poll_wait(filp, &tty->write_wait, wait);
799
800 /* set bits for operations that won't block */
Alan Cox9c1729d2007-07-15 23:39:43 -0700801 if (n_hdlc->rx_buf_list.head)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700802 mask |= POLLIN | POLLRDNORM; /* readable */
803 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
804 mask |= POLLHUP;
Alan Cox9c1729d2007-07-15 23:39:43 -0700805 if (tty_hung_up_p(filp))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700806 mask |= POLLHUP;
Alan Cox9c1729d2007-07-15 23:39:43 -0700807 if (!tty_is_writelocked(tty) &&
808 n_hdlc->tx_free_buf_list.head)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700809 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;
Alan Cox9c1729d2007-07-15 23:39:43 -0700883 if (list->tail)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700884 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);