1 /* generic HDLC line discipline for Linux
2 *
3 * Written by Paul Fulghum paulkf@microgate.com
4 * for Microgate Corporation
5 *
6 * Microgate and SyncLink are registered trademarks of Microgate Corporation
7 *
8 * Adapted from ppp.c, written by Michael Callahan <callahan@maths.ox.ac.uk>,
9 * Al Longyear <longyear@netcom.com>, Paul Mackerras <Paul.Mackerras@cs.anu.edu.au>
10 *
11 * Original release 01/11/99
12 * $Id: n_hdlc.c,v 3.7 2003/05/01 15:45:29 paulkf Exp $
13 *
14 * This code is released under the GNU General Public License (GPL)
15 *
16 * This module implements the tty line discipline N_HDLC for use with
17 * tty device drivers that support bit-synchronous HDLC communications.
18 *
19 * All HDLC data is frame oriented which means:
20 *
21 * 1. tty write calls represent one complete transmit frame of data
22 * The device driver should accept the complete frame or none of
23 * the frame (busy) in the write method. Each write call should have
24 * a byte count in the range of 2-65535 bytes (2 is min HDLC frame
25 * with 1 addr byte and 1 ctrl byte). The max byte count of 65535
26 * should include any crc bytes required. For example, when using
27 * CCITT CRC32, 4 crc bytes are required, so the maximum size frame
28 * the application may transmit is limited to 65531 bytes. For CCITT
29 * CRC16, the maximum application frame size would be 65533.
30 *
31 *
32 * 2. receive callbacks from the device driver represents
33 * one received frame. The device driver should bypass
34 * the tty flip buffer and call the line discipline receive
35 * callback directly to avoid fragmenting or concatenating
36 * multiple frames into a single receive callback.
37 *
38 * The HDLC line discipline queues the receive frames in seperate
39 * buffers so complete receive frames can be returned by the
40 * tty read calls.
41 *
42 * 3. tty read calls returns an entire frame of data or nothing.
43 *
44 * 4. all send and receive data is considered raw. No processing
45 * or translation is performed by the line discipline, regardless
46 * of the tty flags
47 *
48 * 5. When line discipline is queried for the amount of receive
49 * data available (FIOC), 0 is returned if no data available,
50 * otherwise the count of the next available frame is returned.
51 * (instead of the sum of all received frame counts).
52 *
53 * These conventions allow the standard tty programming interface
54 * to be used for synchronous HDLC applications when used with
55 * this line discipline (or another line discipline that is frame
56 * oriented such as N_PPP).
57 *
58 * The SyncLink driver (synclink.c) implements both asynchronous
59 * (using standard line discipline N_TTY) and synchronous HDLC
60 * (using N_HDLC) communications, with the latter using the above
61 * conventions.
62 *
63 * This implementation is very basic and does not maintain
64 * any statistics. The main point is to enforce the raw data
65 * and frame orientation of HDLC communications.
66 *
67 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
68 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
69 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
70 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
71 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
72 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
73 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
74 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
75 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
76 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
77 * OF THE POSSIBILITY OF SUCH DAMAGE.
78 */
79
80 #define HDLC_MAGIC 0x239e
81 #define HDLC_VERSION "$Revision: 3.7 $"
82
83 #include <linux/version.h>
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/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 <asm/system.h>
105 #include <asm/bitops.h>
106 #include <asm/termios.h>
107 #include <linux/if.h>
108
109 #include <linux/ioctl.h>
110
111 #ifdef CONFIG_KERNELD
112 #include <linux/kerneld.h>
113 #endif
114
115 #include <asm/segment.h>
116 #define GET_USER(error,value,addr) error = get_user(value,addr)
117 #define COPY_FROM_USER(error,dest,src,size) error = copy_from_user(dest,src,size) ? -EFAULT : 0
118 #define PUT_USER(error,value,addr) error = put_user(value,addr)
119 #define COPY_TO_USER(error,dest,src,size) error = copy_to_user(dest,src,size) ? -EFAULT : 0
120
121 #include <asm/uaccess.h>
122
123 typedef ssize_t rw_ret_t;
124 typedef size_t rw_count_t;
125
126 /*
127 * Buffers for individual HDLC frames
128 */
129 #define MAX_HDLC_FRAME_SIZE 65535
130 #define DEFAULT_RX_BUF_COUNT 10
131 #define MAX_RX_BUF_COUNT 60
132 #define DEFAULT_TX_BUF_COUNT 1
133
134
135 typedef struct _n_hdlc_buf
136 {
137 struct _n_hdlc_buf *link;
138 int count;
139 char buf[1];
140 } N_HDLC_BUF;
141
142 #define N_HDLC_BUF_SIZE (sizeof(N_HDLC_BUF)+maxframe)
143
144 typedef struct _n_hdlc_buf_list
145 {
146 N_HDLC_BUF *head;
147 N_HDLC_BUF *tail;
148 int count;
149 spinlock_t spinlock;
150
151 } N_HDLC_BUF_LIST;
152
153 /*
154 * Per device instance data structure
155 */
156 struct n_hdlc {
157 int magic; /* magic value for structure */
158 __u32 flags; /* miscellaneous control flags */
159
160 struct tty_struct *tty; /* ptr to TTY structure */
161 struct tty_struct *backup_tty; /* TTY to use if tty gets closed */
162
163 int tbusy; /* reentrancy flag for tx wakeup code */
164 int woke_up;
165 N_HDLC_BUF *tbuf; /* currently transmitting tx buffer */
166 N_HDLC_BUF_LIST tx_buf_list; /* list of pending transmit frame buffers */
167 N_HDLC_BUF_LIST rx_buf_list; /* list of received frame buffers */
168 N_HDLC_BUF_LIST tx_free_buf_list; /* list unused transmit frame buffers */
169 N_HDLC_BUF_LIST rx_free_buf_list; /* list unused received frame buffers */
170 };
171
172 /*
173 * HDLC buffer list manipulation functions
174 */
175 static void n_hdlc_buf_list_init(N_HDLC_BUF_LIST *list);
176 static void n_hdlc_buf_put(N_HDLC_BUF_LIST *list,N_HDLC_BUF *buf);
177 static N_HDLC_BUF* n_hdlc_buf_get(N_HDLC_BUF_LIST *list);
178
179 /* Local functions */
180
181 static struct n_hdlc *n_hdlc_alloc (void);
182
183 MODULE_PARM(debuglevel, "i");
184 MODULE_PARM(maxframe, "i");
185
186 #ifdef MODULE_LICENSE
187 MODULE_LICENSE("GPL");
188 #endif
189
190 /* debug level can be set by insmod for debugging purposes */
191 #define DEBUG_LEVEL_INFO 1
192 static int debuglevel=0;
193
194 /* max frame size for memory allocations */
195 static ssize_t maxframe=4096;
196
197 /* TTY callbacks */
198
199 static rw_ret_t n_hdlc_tty_read(struct tty_struct *,
200 struct file *, __u8 *, rw_count_t);
201 static rw_ret_t n_hdlc_tty_write(struct tty_struct *,
202 struct file *, const __u8 *, rw_count_t);
203 static int n_hdlc_tty_ioctl(struct tty_struct *,
204 struct file *, unsigned int, unsigned long);
205 static unsigned int n_hdlc_tty_poll (struct tty_struct *tty, struct file *filp,
206 poll_table * wait);
207 static int n_hdlc_tty_open (struct tty_struct *);
208 static void n_hdlc_tty_close (struct tty_struct *);
209 static int n_hdlc_tty_room (struct tty_struct *tty);
210 static void n_hdlc_tty_receive (struct tty_struct *tty,
211 const __u8 * cp, char *fp, int count);
212 static void n_hdlc_tty_wakeup (struct tty_struct *tty);
213
214 #define bset(p,b) ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
215
216 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
217 #define n_hdlc2tty(n_hdlc) ((n_hdlc)->tty)
218
219 /* Define this string only once for all macro invocations */
220 static char szVersion[] = HDLC_VERSION;
221
222 /* n_hdlc_release()
223 *
224 * release an n_hdlc per device line discipline info structure
225 *
226 */
n_hdlc_release(struct n_hdlc * n_hdlc)227 static void n_hdlc_release (struct n_hdlc *n_hdlc)
228 {
229 struct tty_struct *tty = n_hdlc2tty (n_hdlc);
230 N_HDLC_BUF *buf;
231
232 if (debuglevel >= DEBUG_LEVEL_INFO)
233 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
234
235 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
236 wake_up_interruptible (&tty->read_wait);
237 wake_up_interruptible (&tty->write_wait);
238
239 if (tty != NULL && tty->disc_data == n_hdlc)
240 tty->disc_data = NULL; /* Break the tty->n_hdlc link */
241
242 /* Release transmit and receive buffers */
243 for(;;) {
244 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
245 if (buf) {
246 kfree(buf);
247 } else
248 break;
249 }
250 for(;;) {
251 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
252 if (buf) {
253 kfree(buf);
254 } else
255 break;
256 }
257 for(;;) {
258 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
259 if (buf) {
260 kfree(buf);
261 } else
262 break;
263 }
264 for(;;) {
265 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
266 if (buf) {
267 kfree(buf);
268 } else
269 break;
270 }
271 if (n_hdlc->tbuf)
272 kfree(n_hdlc->tbuf);
273 kfree(n_hdlc);
274
275 } /* end of n_hdlc_release() */
276
277 /* n_hdlc_tty_close()
278 *
279 * Called when the line discipline is changed to something
280 * else, the tty is closed, or the tty detects a hangup.
281 */
n_hdlc_tty_close(struct tty_struct * tty)282 static void n_hdlc_tty_close(struct tty_struct *tty)
283 {
284 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
285
286 if (debuglevel >= DEBUG_LEVEL_INFO)
287 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
288
289 if (n_hdlc != NULL) {
290 if (n_hdlc->magic != HDLC_MAGIC) {
291 printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
292 return;
293 }
294 #if defined(TTY_NO_WRITE_SPLIT)
295 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
296 #endif
297 tty->disc_data = NULL;
298 if (tty == n_hdlc->backup_tty)
299 n_hdlc->backup_tty = 0;
300 if (tty != n_hdlc->tty)
301 return;
302 if (n_hdlc->backup_tty) {
303 n_hdlc->tty = n_hdlc->backup_tty;
304 } else {
305 n_hdlc_release (n_hdlc);
306 MOD_DEC_USE_COUNT;
307 }
308 }
309
310 if (debuglevel >= DEBUG_LEVEL_INFO)
311 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
312
313 } /* end of n_hdlc_tty_close() */
314
315 /* n_hdlc_tty_open
316 *
317 * called when line discipline changed to n_hdlc
318 *
319 * Arguments: tty pointer to tty info structure
320 * Return Value: 0 if success, otherwise error code
321 */
n_hdlc_tty_open(struct tty_struct * tty)322 static int n_hdlc_tty_open (struct tty_struct *tty)
323 {
324 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
325
326 if (debuglevel >= DEBUG_LEVEL_INFO)
327 printk("%s(%d)n_hdlc_tty_open() called (major=%u,minor=%u)\n",
328 __FILE__,__LINE__,
329 MAJOR(tty->device), MINOR(tty->device));
330
331 /* There should not be an existing table for this slot. */
332 if (n_hdlc) {
333 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
334 return -EEXIST;
335 }
336
337 n_hdlc = n_hdlc_alloc();
338 if (!n_hdlc) {
339 printk (KERN_ERR "n_hdlc_alloc failed\n");
340 return -ENFILE;
341 }
342
343 tty->disc_data = n_hdlc;
344 n_hdlc->tty = tty;
345
346 MOD_INC_USE_COUNT;
347
348 #if defined(TTY_NO_WRITE_SPLIT)
349 /* change tty_io write() to not split large writes into 8K chunks */
350 set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
351 #endif
352
353 /* Flush any pending characters in the driver and discipline. */
354
355 tty_ldisc_flush(tty);
356
357 if (tty->driver.flush_buffer)
358 tty->driver.flush_buffer (tty);
359
360 if (debuglevel >= DEBUG_LEVEL_INFO)
361 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
362
363 return 0;
364
365 } /* end of n_tty_hdlc_open() */
366
367 /* n_hdlc_send_frames()
368 *
369 * send frames on pending send buffer list until the
370 * driver does not accept a frame (busy)
371 * this function is called after adding a frame to the
372 * send buffer list and by the tty wakeup callback
373 *
374 * Arguments: n_hdlc pointer to ldisc instance data
375 * tty pointer to tty instance data
376 * Return Value: None
377 */
n_hdlc_send_frames(struct n_hdlc * n_hdlc,struct tty_struct * tty)378 static void n_hdlc_send_frames (struct n_hdlc *n_hdlc, struct tty_struct *tty)
379 {
380 register int actual;
381 unsigned long flags;
382 N_HDLC_BUF *tbuf;
383
384 if (debuglevel >= DEBUG_LEVEL_INFO)
385 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
386 check_again:
387
388 save_flags(flags);
389 cli ();
390 if (n_hdlc->tbusy) {
391 n_hdlc->woke_up = 1;
392 restore_flags(flags);
393 return;
394 }
395 n_hdlc->tbusy = 1;
396 n_hdlc->woke_up = 0;
397 restore_flags(flags);
398
399 /* get current transmit buffer or get new transmit */
400 /* buffer from list of pending transmit buffers */
401
402 tbuf = n_hdlc->tbuf;
403 if (!tbuf)
404 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
405
406 while (tbuf) {
407 if (debuglevel >= DEBUG_LEVEL_INFO)
408 printk("%s(%d)sending frame %p, count=%d\n",
409 __FILE__,__LINE__,tbuf,tbuf->count);
410
411 /* Send the next block of data to device */
412 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
413 actual = tty->driver.write(tty, 0, tbuf->buf, tbuf->count);
414
415 /* if transmit error, throw frame away by */
416 /* pretending it was accepted by driver */
417 if (actual < 0)
418 actual = tbuf->count;
419
420 if (actual == tbuf->count) {
421 if (debuglevel >= DEBUG_LEVEL_INFO)
422 printk("%s(%d)frame %p completed\n",
423 __FILE__,__LINE__,tbuf);
424
425 /* free current transmit buffer */
426 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,tbuf);
427
428 /* this tx buffer is done */
429 n_hdlc->tbuf = NULL;
430
431 /* wait up sleeping writers */
432 wake_up_interruptible(&tty->write_wait);
433
434 /* get next pending transmit buffer */
435 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
436 } else {
437 if (debuglevel >= DEBUG_LEVEL_INFO)
438 printk("%s(%d)frame %p pending\n",
439 __FILE__,__LINE__,tbuf);
440
441 /* buffer not accepted by driver */
442 /* set this buffer as pending buffer */
443 n_hdlc->tbuf = tbuf;
444 break;
445 }
446 }
447
448 if (!tbuf)
449 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
450
451 /* Clear the re-entry flag */
452 save_flags(flags);
453 cli ();
454 n_hdlc->tbusy = 0;
455 restore_flags(flags);
456
457 if (n_hdlc->woke_up)
458 goto check_again;
459
460 if (debuglevel >= DEBUG_LEVEL_INFO)
461 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
462
463 } /* end of n_hdlc_send_frames() */
464
465 /* n_hdlc_tty_wakeup()
466 *
467 * Callback for transmit wakeup. Called when low level
468 * device driver can accept more send data.
469 *
470 * Arguments: tty pointer to associated tty instance data
471 * Return Value: None
472 */
n_hdlc_tty_wakeup(struct tty_struct * tty)473 static void n_hdlc_tty_wakeup (struct tty_struct *tty)
474 {
475 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
476
477 if (debuglevel >= DEBUG_LEVEL_INFO)
478 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
479
480 if (!n_hdlc)
481 return;
482
483 if (tty != n_hdlc->tty) {
484 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
485 return;
486 }
487
488 n_hdlc_send_frames (n_hdlc, tty);
489
490 } /* end of n_hdlc_tty_wakeup() */
491
492 /* n_hdlc_tty_room()
493 *
494 * Callback function from tty driver. Return the amount of
495 * space left in the receiver's buffer to decide if remote
496 * transmitter is to be throttled.
497 *
498 * Arguments: tty pointer to associated tty instance data
499 * Return Value: number of bytes left in receive buffer
500 */
n_hdlc_tty_room(struct tty_struct * tty)501 static int n_hdlc_tty_room (struct tty_struct *tty)
502 {
503 if (debuglevel >= DEBUG_LEVEL_INFO)
504 printk("%s(%d)n_hdlc_tty_room() called\n",__FILE__,__LINE__);
505 /* always return a larger number to prevent */
506 /* throttling of remote transmitter. */
507 return 65536;
508 } /* end of n_hdlc_tty_root() */
509
510 /* n_hdlc_tty_receive()
511 *
512 * Called by tty low level driver when receive data is
513 * available. Data is interpreted as one HDLC frame.
514 *
515 * Arguments: tty pointer to tty isntance data
516 * data pointer to received data
517 * flags pointer to flags for data
518 * count count of received data in bytes
519 *
520 * Return Value: None
521 */
n_hdlc_tty_receive(struct tty_struct * tty,const __u8 * data,char * flags,int count)522 static void n_hdlc_tty_receive(struct tty_struct *tty,
523 const __u8 * data, char *flags, int count)
524 {
525 register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
526 register N_HDLC_BUF *buf;
527
528 if (debuglevel >= DEBUG_LEVEL_INFO)
529 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
530 __FILE__,__LINE__, count);
531
532 /* This can happen if stuff comes in on the backup tty */
533 if (n_hdlc == 0 || tty != n_hdlc->tty)
534 return;
535
536 /* verify line is using HDLC discipline */
537 if (n_hdlc->magic != HDLC_MAGIC) {
538 printk("%s(%d) line not using HDLC discipline\n",
539 __FILE__,__LINE__);
540 return;
541 }
542
543 if ( count>maxframe ) {
544 if (debuglevel >= DEBUG_LEVEL_INFO)
545 printk("%s(%d) rx count>maxframesize, data discarded\n",
546 __FILE__,__LINE__);
547 return;
548 }
549
550 /* get a free HDLC buffer */
551 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
552 if (!buf) {
553 /* no buffers in free list, attempt to allocate another rx buffer */
554 /* unless the maximum count has been reached */
555 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
556 buf = (N_HDLC_BUF*)kmalloc(N_HDLC_BUF_SIZE,GFP_ATOMIC);
557 }
558
559 if (!buf) {
560 if (debuglevel >= DEBUG_LEVEL_INFO)
561 printk("%s(%d) no more rx buffers, data discarded\n",
562 __FILE__,__LINE__);
563 return;
564 }
565
566 /* copy received data to HDLC buffer */
567 memcpy(buf->buf,data,count);
568 buf->count=count;
569
570 /* add HDLC buffer to list of received frames */
571 n_hdlc_buf_put(&n_hdlc->rx_buf_list,buf);
572
573 /* wake up any blocked reads and perform async signalling */
574 wake_up_interruptible (&tty->read_wait);
575 if (n_hdlc->tty->fasync != NULL)
576 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
577
578 } /* end of n_hdlc_tty_receive() */
579
580 /* n_hdlc_tty_read()
581 *
582 * Called to retreive one frame of data (if available)
583 *
584 * Arguments:
585 *
586 * tty pointer to tty instance data
587 * file pointer to open file object
588 * buf pointer to returned data buffer
589 * nr size of returned data buffer
590 *
591 * Return Value:
592 *
593 * Number of bytes returned or error code
594 */
n_hdlc_tty_read(struct tty_struct * tty,struct file * file,__u8 * buf,rw_count_t nr)595 static rw_ret_t n_hdlc_tty_read (struct tty_struct *tty,
596 struct file *file, __u8 * buf, rw_count_t nr)
597 {
598 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
599 int error;
600 rw_ret_t ret;
601 N_HDLC_BUF *rbuf;
602
603 if (debuglevel >= DEBUG_LEVEL_INFO)
604 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
605
606 /* Validate the pointers */
607 if (!n_hdlc)
608 return -EIO;
609
610 /* verify user access to buffer */
611 error = verify_area (VERIFY_WRITE, buf, nr);
612 if (error != 0) {
613 printk(KERN_WARNING"%s(%d) n_hdlc_tty_read() can't verify user "
614 "buffer\n",__FILE__,__LINE__);
615 return (error);
616 }
617
618 for (;;) {
619 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
620 return -EIO;
621
622 n_hdlc = tty2n_hdlc (tty);
623 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
624 tty != n_hdlc->tty)
625 return 0;
626
627 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
628 if (rbuf)
629 break;
630
631 /* no data */
632 if (file->f_flags & O_NONBLOCK)
633 return -EAGAIN;
634
635 interruptible_sleep_on (&tty->read_wait);
636 if (signal_pending(current))
637 return -EINTR;
638 }
639
640 if (rbuf->count > nr) {
641 /* frame too large for caller's buffer (discard frame) */
642 ret = (rw_ret_t)-EOVERFLOW;
643 } else {
644 /* Copy the data to the caller's buffer */
645 COPY_TO_USER(error,buf,rbuf->buf,rbuf->count);
646 if (error)
647 ret = (rw_ret_t)error;
648 else
649 ret = (rw_ret_t)rbuf->count;
650 }
651
652 /* return HDLC buffer to free list unless the free list */
653 /* count has exceeded the default value, in which case the */
654 /* buffer is freed back to the OS to conserve memory */
655 if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
656 kfree(rbuf);
657 else
658 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
659
660 return ret;
661
662 } /* end of n_hdlc_tty_read() */
663
664 /* n_hdlc_tty_write()
665 *
666 * write a single frame of data to device
667 *
668 * Arguments: tty pointer to associated tty device instance data
669 * file pointer to file object data
670 * data pointer to transmit data (one frame)
671 * count size of transmit frame in bytes
672 *
673 * Return Value: number of bytes written (or error code)
674 */
n_hdlc_tty_write(struct tty_struct * tty,struct file * file,const __u8 * data,rw_count_t count)675 static rw_ret_t n_hdlc_tty_write (struct tty_struct *tty, struct file *file,
676 const __u8 * data, rw_count_t count)
677 {
678 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
679 int error = 0;
680 DECLARE_WAITQUEUE(wait, current);
681 N_HDLC_BUF *tbuf;
682
683 if (debuglevel >= DEBUG_LEVEL_INFO)
684 printk("%s(%d)n_hdlc_tty_write() called count=%d\n",
685 __FILE__,__LINE__,count);
686
687 /* Verify pointers */
688 if (!n_hdlc)
689 return -EIO;
690
691 if (n_hdlc->magic != HDLC_MAGIC)
692 return -EIO;
693
694 /* verify frame size */
695 if (count > maxframe ) {
696 if (debuglevel & DEBUG_LEVEL_INFO)
697 printk (KERN_WARNING
698 "n_hdlc_tty_write: truncating user packet "
699 "from %lu to %d\n", (unsigned long) count,
700 maxframe );
701 count = maxframe;
702 }
703
704 add_wait_queue(&tty->write_wait, &wait);
705 set_current_state(TASK_INTERRUPTIBLE);
706
707 /* Allocate transmit buffer */
708 /* sleep until transmit buffer available */
709 while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
710 schedule();
711
712 n_hdlc = tty2n_hdlc (tty);
713 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
714 tty != n_hdlc->tty) {
715 printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
716 error = -EIO;
717 break;
718 }
719
720 if (signal_pending(current)) {
721 error = -EINTR;
722 break;
723 }
724 }
725
726 set_current_state(TASK_RUNNING);
727 remove_wait_queue(&tty->write_wait, &wait);
728
729 if (!error) {
730 /* Retrieve the user's buffer */
731 COPY_FROM_USER (error, tbuf->buf, data, count);
732 if (error) {
733 /* return tx buffer to free list */
734 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,tbuf);
735 } else {
736 /* Send the data */
737 tbuf->count = error = count;
738 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
739 n_hdlc_send_frames(n_hdlc,tty);
740 }
741 }
742
743 return error;
744
745 } /* end of n_hdlc_tty_write() */
746
747 /* n_hdlc_tty_ioctl()
748 *
749 * Process IOCTL system call for the tty device.
750 *
751 * Arguments:
752 *
753 * tty pointer to tty instance data
754 * file pointer to open file object for device
755 * cmd IOCTL command code
756 * arg argument for IOCTL call (cmd dependent)
757 *
758 * Return Value: Command dependent
759 */
n_hdlc_tty_ioctl(struct tty_struct * tty,struct file * file,unsigned int cmd,unsigned long arg)760 static int n_hdlc_tty_ioctl (struct tty_struct *tty, struct file * file,
761 unsigned int cmd, unsigned long arg)
762 {
763 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
764 int error = 0;
765 int count;
766 unsigned long flags;
767
768 if (debuglevel >= DEBUG_LEVEL_INFO)
769 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
770 __FILE__,__LINE__,cmd);
771
772 /* Verify the status of the device */
773 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
774 return -EBADF;
775
776 switch (cmd) {
777 case FIONREAD:
778 /* report count of read data available */
779 /* in next available frame (if any) */
780 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
781 if (n_hdlc->rx_buf_list.head)
782 count = n_hdlc->rx_buf_list.head->count;
783 else
784 count = 0;
785 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
786 PUT_USER (error, count, (int *) arg);
787 break;
788
789 case TIOCOUTQ:
790 /* get the pending tx byte count in the driver */
791 count = tty->driver.chars_in_buffer ?
792 tty->driver.chars_in_buffer(tty) : 0;
793 /* add size of next output frame in queue */
794 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
795 if (n_hdlc->tx_buf_list.head)
796 count += n_hdlc->tx_buf_list.head->count;
797 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
798 PUT_USER (error, count, (int*)arg);
799 break;
800
801 default:
802 error = n_tty_ioctl (tty, file, cmd, arg);
803 break;
804 }
805 return error;
806
807 } /* end of n_hdlc_tty_ioctl() */
808
809 /* n_hdlc_tty_poll()
810 *
811 * TTY callback for poll system call. Determine which
812 * operations (read/write) will not block and return
813 * info to caller.
814 *
815 * Arguments:
816 *
817 * tty pointer to tty instance data
818 * filp pointer to open file object for device
819 * poll_table wait queue for operations
820 *
821 * Return Value:
822 *
823 * bit mask containing info on which ops will not block
824 */
n_hdlc_tty_poll(struct tty_struct * tty,struct file * filp,poll_table * wait)825 static unsigned int n_hdlc_tty_poll (struct tty_struct *tty,
826 struct file *filp, poll_table * wait)
827 {
828 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
829 unsigned int mask = 0;
830
831 if (debuglevel >= DEBUG_LEVEL_INFO)
832 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
833
834 if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
835 /* queue current process into any wait queue that */
836 /* may awaken in the future (read and write) */
837
838 poll_wait(filp, &tty->read_wait, wait);
839 poll_wait(filp, &tty->write_wait, wait);
840
841 /* set bits for operations that wont block */
842 if(n_hdlc->rx_buf_list.head)
843 mask |= POLLIN | POLLRDNORM; /* readable */
844 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
845 mask |= POLLHUP;
846 if(tty_hung_up_p(filp))
847 mask |= POLLHUP;
848 if(n_hdlc->tx_free_buf_list.head)
849 mask |= POLLOUT | POLLWRNORM; /* writable */
850 }
851 return mask;
852 } /* end of n_hdlc_tty_poll() */
853
854 /* n_hdlc_alloc()
855 *
856 * Allocate an n_hdlc instance data structure
857 *
858 * Arguments: None
859 * Return Value: pointer to structure if success, otherwise 0
860 */
n_hdlc_alloc(void)861 static struct n_hdlc *n_hdlc_alloc (void)
862 {
863 struct n_hdlc *n_hdlc;
864 N_HDLC_BUF *buf;
865 int i;
866
867 n_hdlc = (struct n_hdlc *)kmalloc(sizeof(struct n_hdlc), GFP_KERNEL);
868 if (!n_hdlc)
869 return 0;
870
871 memset(n_hdlc, 0, sizeof(*n_hdlc));
872
873 n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
874 n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
875 n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
876 n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
877
878 /* allocate free rx buffer list */
879 for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
880 buf = (N_HDLC_BUF*)kmalloc(N_HDLC_BUF_SIZE,GFP_KERNEL);
881 if (buf)
882 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
883 else if (debuglevel >= DEBUG_LEVEL_INFO)
884 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
885 }
886
887 /* allocate free tx buffer list */
888 for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
889 buf = (N_HDLC_BUF*)kmalloc(N_HDLC_BUF_SIZE,GFP_KERNEL);
890 if (buf)
891 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
892 else if (debuglevel >= DEBUG_LEVEL_INFO)
893 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
894 }
895
896 /* Initialize the control block */
897 n_hdlc->magic = HDLC_MAGIC;
898 n_hdlc->flags = 0;
899
900 return n_hdlc;
901
902 } /* end of n_hdlc_alloc() */
903
904 /* n_hdlc_buf_list_init()
905 *
906 * initialize specified HDLC buffer list
907 *
908 * Arguments: list pointer to buffer list
909 * Return Value: None
910 */
n_hdlc_buf_list_init(N_HDLC_BUF_LIST * list)911 static void n_hdlc_buf_list_init(N_HDLC_BUF_LIST *list)
912 {
913 memset(list,0,sizeof(N_HDLC_BUF_LIST));
914 spin_lock_init(&list->spinlock);
915 } /* end of n_hdlc_buf_list_init() */
916
917 /* n_hdlc_buf_put()
918 *
919 * add specified HDLC buffer to tail of specified list
920 *
921 * Arguments:
922 *
923 * list pointer to buffer list
924 * buf pointer to buffer
925 *
926 * Return Value: None
927 */
n_hdlc_buf_put(N_HDLC_BUF_LIST * list,N_HDLC_BUF * buf)928 static void n_hdlc_buf_put(N_HDLC_BUF_LIST *list,N_HDLC_BUF *buf)
929 {
930 unsigned long flags;
931 spin_lock_irqsave(&list->spinlock,flags);
932
933 buf->link=NULL;
934 if(list->tail)
935 list->tail->link = buf;
936 else
937 list->head = buf;
938 list->tail = buf;
939 (list->count)++;
940
941 spin_unlock_irqrestore(&list->spinlock,flags);
942
943 } /* end of n_hdlc_buf_put() */
944
945 /* n_hdlc_buf_get()
946 *
947 * remove and return an HDLC buffer from the
948 * head of the specified HDLC buffer list
949 *
950 * Arguments:
951 *
952 * list pointer to HDLC buffer list
953 *
954 * Return Value:
955 *
956 * pointer to HDLC buffer if available, otherwise NULL
957 */
n_hdlc_buf_get(N_HDLC_BUF_LIST * list)958 static N_HDLC_BUF* n_hdlc_buf_get(N_HDLC_BUF_LIST *list)
959 {
960 unsigned long flags;
961 N_HDLC_BUF *buf;
962 spin_lock_irqsave(&list->spinlock,flags);
963
964 buf = list->head;
965 if (buf) {
966 list->head = buf->link;
967 (list->count)--;
968 }
969 if (!list->head)
970 list->tail = NULL;
971
972 spin_unlock_irqrestore(&list->spinlock,flags);
973 return buf;
974
975 } /* end of n_hdlc_buf_get() */
976
n_hdlc_init(void)977 static int __init n_hdlc_init(void)
978 {
979 static struct tty_ldisc n_hdlc_ldisc;
980 int status;
981
982 /* range check maxframe arg */
983 if ( maxframe<4096)
984 maxframe=4096;
985 else if ( maxframe>65535)
986 maxframe=65535;
987
988 printk("HDLC line discipline: version %s, maxframe=%u\n",
989 szVersion, maxframe);
990
991 /* Register the tty discipline */
992
993 memset(&n_hdlc_ldisc, 0, sizeof (n_hdlc_ldisc));
994 n_hdlc_ldisc.magic = TTY_LDISC_MAGIC;
995 n_hdlc_ldisc.name = "hdlc";
996 n_hdlc_ldisc.open = n_hdlc_tty_open;
997 n_hdlc_ldisc.close = n_hdlc_tty_close;
998 n_hdlc_ldisc.read = n_hdlc_tty_read;
999 n_hdlc_ldisc.write = n_hdlc_tty_write;
1000 n_hdlc_ldisc.ioctl = n_hdlc_tty_ioctl;
1001 n_hdlc_ldisc.poll = n_hdlc_tty_poll;
1002 n_hdlc_ldisc.receive_room = n_hdlc_tty_room;
1003 n_hdlc_ldisc.receive_buf = n_hdlc_tty_receive;
1004 n_hdlc_ldisc.write_wakeup = n_hdlc_tty_wakeup;
1005
1006 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
1007 if (!status)
1008 printk (KERN_INFO"N_HDLC line discipline registered.\n");
1009 else
1010 printk (KERN_ERR"error registering line discipline: %d\n",status);
1011
1012 if (status)
1013 printk(KERN_INFO"N_HDLC: init failure %d\n", status);
1014 return (status);
1015
1016 } /* end of init_module() */
1017
n_hdlc_exit(void)1018 static void __exit n_hdlc_exit(void)
1019 {
1020 int status;
1021 /* Release tty registration of line discipline */
1022 if ((status = tty_register_ldisc(N_HDLC, NULL)))
1023 printk("N_HDLC: can't unregister line discipline (err = %d)\n", status);
1024 else
1025 printk("N_HDLC: line discipline unregistered\n");
1026 }
1027
1028 module_init(n_hdlc_init);
1029 module_exit(n_hdlc_exit);
1030
1031 EXPORT_NO_SYMBOLS;
1032