GNU Linux-libre 4.9.309-gnu1
[releases.git] / drivers / tty / n_hdlc.c
1 /* generic HDLC line discipline for Linux
2  *
3  * Written by Paul Fulghum paulkf@microgate.com
4  * for Microgate Corporation
5  *
6  * Microgate and SyncLink are registered trademarks of Microgate Corporation
7  *
8  * Adapted from ppp.c, written by Michael Callahan <callahan@maths.ox.ac.uk>,
9  *      Al Longyear <longyear@netcom.com>,
10  *      Paul Mackerras <Paul.Mackerras@cs.anu.edu.au>
11  *
12  * Original release 01/11/99
13  *
14  * This code is released under the GNU General Public License (GPL)
15  *
16  * This module implements the tty line discipline N_HDLC for use with
17  * tty device drivers that support bit-synchronous HDLC communications.
18  *
19  * All HDLC data is frame oriented which means:
20  *
21  * 1. tty write calls represent one complete transmit frame of data
22  *    The device driver should accept the complete frame or none of 
23  *    the frame (busy) in the write method. Each write call should have
24  *    a byte count in the range of 2-65535 bytes (2 is min HDLC frame
25  *    with 1 addr byte and 1 ctrl byte). The max byte count of 65535
26  *    should include any crc bytes required. For example, when using
27  *    CCITT CRC32, 4 crc bytes are required, so the maximum size frame
28  *    the application may transmit is limited to 65531 bytes. For CCITT
29  *    CRC16, the maximum application frame size would be 65533.
30  *
31  *
32  * 2. receive callbacks from the device driver represents
33  *    one received frame. The device driver should bypass
34  *    the tty flip buffer and call the line discipline receive
35  *    callback directly to avoid fragmenting or concatenating
36  *    multiple frames into a single receive callback.
37  *
38  *    The HDLC line discipline queues the receive frames in separate
39  *    buffers so complete receive frames can be returned by the
40  *    tty read calls.
41  *
42  * 3. tty read calls returns an entire frame of data or nothing.
43  *    
44  * 4. all send and receive data is considered raw. No processing
45  *    or translation is performed by the line discipline, regardless
46  *    of the tty flags
47  *
48  * 5. When line discipline is queried for the amount of receive
49  *    data available (FIOC), 0 is returned if no data available,
50  *    otherwise the count of the next available frame is returned.
51  *    (instead of the sum of all received frame counts).
52  *
53  * These conventions allow the standard tty programming interface
54  * to be used for synchronous HDLC applications when used with
55  * this line discipline (or another line discipline that is frame
56  * oriented such as N_PPP).
57  *
58  * The SyncLink driver (synclink.c) implements both asynchronous
59  * (using standard line discipline N_TTY) and synchronous HDLC
60  * (using N_HDLC) communications, with the latter using the above
61  * conventions.
62  *
63  * This implementation is very basic and does not maintain
64  * any statistics. The main point is to enforce the raw data
65  * and frame orientation of HDLC communications.
66  *
67  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
68  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
69  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
70  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
71  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
72  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
73  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
74  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
75  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
76  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
77  * OF THE POSSIBILITY OF SUCH DAMAGE.
78  */
79
80 #define HDLC_MAGIC 0x239e
81
82 #include <linux/module.h>
83 #include <linux/init.h>
84 #include <linux/kernel.h>
85 #include <linux/sched.h>
86 #include <linux/types.h>
87 #include <linux/fcntl.h>
88 #include <linux/interrupt.h>
89 #include <linux/ptrace.h>
90
91 #undef VERSION
92 #define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
93
94 #include <linux/poll.h>
95 #include <linux/in.h>
96 #include <linux/ioctl.h>
97 #include <linux/slab.h>
98 #include <linux/tty.h>
99 #include <linux/errno.h>
100 #include <linux/string.h>       /* used in new tty drivers */
101 #include <linux/signal.h>       /* used in new tty drivers */
102 #include <linux/if.h>
103 #include <linux/bitops.h>
104
105 #include <asm/termios.h>
106 #include <asm/uaccess.h>
107
108 /*
109  * Buffers for individual HDLC frames
110  */
111 #define MAX_HDLC_FRAME_SIZE 65535 
112 #define DEFAULT_RX_BUF_COUNT 10
113 #define MAX_RX_BUF_COUNT 60
114 #define DEFAULT_TX_BUF_COUNT 3
115
116 struct n_hdlc_buf {
117         struct list_head  list_item;
118         int               count;
119         char              buf[1];
120 };
121
122 #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
123
124 struct n_hdlc_buf_list {
125         struct list_head  list;
126         int               count;
127         spinlock_t        spinlock;
128 };
129
130 /**
131  * struct n_hdlc - per device instance data structure
132  * @magic - magic value for structure
133  * @flags - miscellaneous control flags
134  * @tty - ptr to TTY structure
135  * @backup_tty - TTY to use if tty gets closed
136  * @tbusy - reentrancy flag for tx wakeup code
137  * @woke_up - FIXME: describe this field
138  * @tx_buf_list - list of pending transmit frame buffers
139  * @rx_buf_list - list of received frame buffers
140  * @tx_free_buf_list - list unused transmit frame buffers
141  * @rx_free_buf_list - list unused received frame buffers
142  */
143 struct n_hdlc {
144         int                     magic;
145         __u32                   flags;
146         struct tty_struct       *tty;
147         struct tty_struct       *backup_tty;
148         int                     tbusy;
149         int                     woke_up;
150         struct n_hdlc_buf_list  tx_buf_list;
151         struct n_hdlc_buf_list  rx_buf_list;
152         struct n_hdlc_buf_list  tx_free_buf_list;
153         struct n_hdlc_buf_list  rx_free_buf_list;
154 };
155
156 /*
157  * HDLC buffer list manipulation functions
158  */
159 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
160                                                 struct n_hdlc_buf *buf);
161 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
162                            struct n_hdlc_buf *buf);
163 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
164
165 /* Local functions */
166
167 static struct n_hdlc *n_hdlc_alloc (void);
168
169 /* debug level can be set by insmod for debugging purposes */
170 #define DEBUG_LEVEL_INFO        1
171 static int debuglevel;
172
173 /* max frame size for memory allocations */
174 static int maxframe = 4096;
175
176 /* TTY callbacks */
177
178 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
179                            __u8 __user *buf, size_t nr);
180 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
181                             const unsigned char *buf, size_t nr);
182 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
183                             unsigned int cmd, unsigned long arg);
184 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
185                                     poll_table *wait);
186 static int n_hdlc_tty_open(struct tty_struct *tty);
187 static void n_hdlc_tty_close(struct tty_struct *tty);
188 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
189                                char *fp, int count);
190 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
191
192 #define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
193
194 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
195 #define n_hdlc2tty(n_hdlc)      ((n_hdlc)->tty)
196
197 static void flush_rx_queue(struct tty_struct *tty)
198 {
199         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
200         struct n_hdlc_buf *buf;
201
202         while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
203                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
204 }
205
206 static void flush_tx_queue(struct tty_struct *tty)
207 {
208         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
209         struct n_hdlc_buf *buf;
210
211         while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
212                 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
213 }
214
215 static struct tty_ldisc_ops n_hdlc_ldisc = {
216         .owner          = THIS_MODULE,
217         .magic          = TTY_LDISC_MAGIC,
218         .name           = "hdlc",
219         .open           = n_hdlc_tty_open,
220         .close          = n_hdlc_tty_close,
221         .read           = n_hdlc_tty_read,
222         .write          = n_hdlc_tty_write,
223         .ioctl          = n_hdlc_tty_ioctl,
224         .poll           = n_hdlc_tty_poll,
225         .receive_buf    = n_hdlc_tty_receive,
226         .write_wakeup   = n_hdlc_tty_wakeup,
227         .flush_buffer   = flush_rx_queue,
228 };
229
230 /**
231  * n_hdlc_release - release an n_hdlc per device line discipline info structure
232  * @n_hdlc - per device line discipline info structure
233  */
234 static void n_hdlc_release(struct n_hdlc *n_hdlc)
235 {
236         struct tty_struct *tty = n_hdlc2tty (n_hdlc);
237         struct n_hdlc_buf *buf;
238         
239         if (debuglevel >= DEBUG_LEVEL_INFO)     
240                 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
241                 
242         /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
243         wake_up_interruptible (&tty->read_wait);
244         wake_up_interruptible (&tty->write_wait);
245
246         if (tty->disc_data == n_hdlc)
247                 tty->disc_data = NULL;  /* Break the tty->n_hdlc link */
248
249         /* Release transmit and receive buffers */
250         for(;;) {
251                 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
252                 if (buf) {
253                         kfree(buf);
254                 } else
255                         break;
256         }
257         for(;;) {
258                 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
259                 if (buf) {
260                         kfree(buf);
261                 } else
262                         break;
263         }
264         for(;;) {
265                 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
266                 if (buf) {
267                         kfree(buf);
268                 } else
269                         break;
270         }
271         for(;;) {
272                 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
273                 if (buf) {
274                         kfree(buf);
275                 } else
276                         break;
277         }
278         kfree(n_hdlc);
279         
280 }       /* end of n_hdlc_release() */
281
282 /**
283  * n_hdlc_tty_close - line discipline close
284  * @tty - pointer to tty info structure
285  *
286  * Called when the line discipline is changed to something
287  * else, the tty is closed, or the tty detects a hangup.
288  */
289 static void n_hdlc_tty_close(struct tty_struct *tty)
290 {
291         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
292
293         if (debuglevel >= DEBUG_LEVEL_INFO)     
294                 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
295                 
296         if (n_hdlc != NULL) {
297                 if (n_hdlc->magic != HDLC_MAGIC) {
298                         printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
299                         return;
300                 }
301 #if defined(TTY_NO_WRITE_SPLIT)
302                 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
303 #endif
304                 tty->disc_data = NULL;
305                 if (tty == n_hdlc->backup_tty)
306                         n_hdlc->backup_tty = NULL;
307                 if (tty != n_hdlc->tty)
308                         return;
309                 if (n_hdlc->backup_tty) {
310                         n_hdlc->tty = n_hdlc->backup_tty;
311                 } else {
312                         n_hdlc_release (n_hdlc);
313                 }
314         }
315         
316         if (debuglevel >= DEBUG_LEVEL_INFO)     
317                 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
318                 
319 }       /* end of n_hdlc_tty_close() */
320
321 /**
322  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
323  * @tty - pointer to tty info structure
324  *
325  * Returns 0 if success, otherwise error code
326  */
327 static int n_hdlc_tty_open (struct tty_struct *tty)
328 {
329         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
330
331         if (debuglevel >= DEBUG_LEVEL_INFO)     
332                 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
333                 __FILE__,__LINE__,
334                 tty->name);
335                 
336         /* There should not be an existing table for this slot. */
337         if (n_hdlc) {
338                 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
339                 return -EEXIST;
340         }
341         
342         n_hdlc = n_hdlc_alloc();
343         if (!n_hdlc) {
344                 printk (KERN_ERR "n_hdlc_alloc failed\n");
345                 return -ENFILE;
346         }
347                 
348         tty->disc_data = n_hdlc;
349         n_hdlc->tty    = tty;
350         tty->receive_room = 65536;
351         
352 #if defined(TTY_NO_WRITE_SPLIT)
353         /* change tty_io write() to not split large writes into 8K chunks */
354         set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
355 #endif
356         
357         /* flush receive data from driver */
358         tty_driver_flush_buffer(tty);
359                 
360         if (debuglevel >= DEBUG_LEVEL_INFO)     
361                 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
362                 
363         return 0;
364         
365 }       /* end of n_tty_hdlc_open() */
366
367 /**
368  * n_hdlc_send_frames - send frames on pending send buffer list
369  * @n_hdlc - pointer to ldisc instance data
370  * @tty - pointer to tty instance data
371  *
372  * Send frames on pending send buffer list until the driver does not accept a
373  * frame (busy) this function is called after adding a frame to the send buffer
374  * list and by the tty wakeup callback.
375  */
376 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
377 {
378         register int actual;
379         unsigned long flags;
380         struct n_hdlc_buf *tbuf;
381
382         if (debuglevel >= DEBUG_LEVEL_INFO)     
383                 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
384  check_again:
385                 
386         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
387         if (n_hdlc->tbusy) {
388                 n_hdlc->woke_up = 1;
389                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
390                 return;
391         }
392         n_hdlc->tbusy = 1;
393         n_hdlc->woke_up = 0;
394         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
395
396         tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
397         while (tbuf) {
398                 if (debuglevel >= DEBUG_LEVEL_INFO)     
399                         printk("%s(%d)sending frame %p, count=%d\n",
400                                 __FILE__,__LINE__,tbuf,tbuf->count);
401                         
402                 /* Send the next block of data to device */
403                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
404                 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
405
406                 /* rollback was possible and has been done */
407                 if (actual == -ERESTARTSYS) {
408                         n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
409                         break;
410                 }
411                 /* if transmit error, throw frame away by */
412                 /* pretending it was accepted by driver */
413                 if (actual < 0)
414                         actual = tbuf->count;
415                 
416                 if (actual == tbuf->count) {
417                         if (debuglevel >= DEBUG_LEVEL_INFO)     
418                                 printk("%s(%d)frame %p completed\n",
419                                         __FILE__,__LINE__,tbuf);
420                                         
421                         /* free current transmit buffer */
422                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
423
424                         /* wait up sleeping writers */
425                         wake_up_interruptible(&tty->write_wait);
426         
427                         /* get next pending transmit buffer */
428                         tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
429                 } else {
430                         if (debuglevel >= DEBUG_LEVEL_INFO)     
431                                 printk("%s(%d)frame %p pending\n",
432                                         __FILE__,__LINE__,tbuf);
433
434                         /*
435                          * the buffer was not accepted by driver,
436                          * return it back into tx queue
437                          */
438                         n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
439                         break;
440                 }
441         }
442         
443         if (!tbuf)
444                 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
445         
446         /* Clear the re-entry flag */
447         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
448         n_hdlc->tbusy = 0;
449         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 
450         
451         if (n_hdlc->woke_up)
452           goto check_again;
453
454         if (debuglevel >= DEBUG_LEVEL_INFO)     
455                 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
456                 
457 }       /* end of n_hdlc_send_frames() */
458
459 /**
460  * n_hdlc_tty_wakeup - Callback for transmit wakeup
461  * @tty - pointer to associated tty instance data
462  *
463  * Called when low level device driver can accept more send data.
464  */
465 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
466 {
467         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
468
469         if (debuglevel >= DEBUG_LEVEL_INFO)     
470                 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
471                 
472         if (!n_hdlc)
473                 return;
474
475         if (tty != n_hdlc->tty) {
476                 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
477                 return;
478         }
479
480         n_hdlc_send_frames (n_hdlc, tty);
481                 
482 }       /* end of n_hdlc_tty_wakeup() */
483
484 /**
485  * n_hdlc_tty_receive - Called by tty driver when receive data is available
486  * @tty - pointer to tty instance data
487  * @data - pointer to received data
488  * @flags - pointer to flags for data
489  * @count - count of received data in bytes
490  *
491  * Called by tty low level driver when receive data is available. Data is
492  * interpreted as one HDLC frame.
493  */
494 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
495                                char *flags, int count)
496 {
497         register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
498         register struct n_hdlc_buf *buf;
499
500         if (debuglevel >= DEBUG_LEVEL_INFO)     
501                 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
502                         __FILE__,__LINE__, count);
503                 
504         /* This can happen if stuff comes in on the backup tty */
505         if (!n_hdlc || tty != n_hdlc->tty)
506                 return;
507                 
508         /* verify line is using HDLC discipline */
509         if (n_hdlc->magic != HDLC_MAGIC) {
510                 printk("%s(%d) line not using HDLC discipline\n",
511                         __FILE__,__LINE__);
512                 return;
513         }
514         
515         if ( count>maxframe ) {
516                 if (debuglevel >= DEBUG_LEVEL_INFO)     
517                         printk("%s(%d) rx count>maxframesize, data discarded\n",
518                                __FILE__,__LINE__);
519                 return;
520         }
521
522         /* get a free HDLC buffer */    
523         buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
524         if (!buf) {
525                 /* no buffers in free list, attempt to allocate another rx buffer */
526                 /* unless the maximum count has been reached */
527                 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
528                         buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
529         }
530         
531         if (!buf) {
532                 if (debuglevel >= DEBUG_LEVEL_INFO)     
533                         printk("%s(%d) no more rx buffers, data discarded\n",
534                                __FILE__,__LINE__);
535                 return;
536         }
537                 
538         /* copy received data to HDLC buffer */
539         memcpy(buf->buf,data,count);
540         buf->count=count;
541
542         /* add HDLC buffer to list of received frames */
543         n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
544         
545         /* wake up any blocked reads and perform async signalling */
546         wake_up_interruptible (&tty->read_wait);
547         if (n_hdlc->tty->fasync != NULL)
548                 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
549
550 }       /* end of n_hdlc_tty_receive() */
551
552 /**
553  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
554  * @tty - pointer to tty instance data
555  * @file - pointer to open file object
556  * @buf - pointer to returned data buffer
557  * @nr - size of returned data buffer
558  *      
559  * Returns the number of bytes returned or error code.
560  */
561 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
562                            __u8 __user *buf, size_t nr)
563 {
564         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
565         int ret = 0;
566         struct n_hdlc_buf *rbuf;
567         DECLARE_WAITQUEUE(wait, current);
568
569         if (debuglevel >= DEBUG_LEVEL_INFO)     
570                 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
571                 
572         /* Validate the pointers */
573         if (!n_hdlc)
574                 return -EIO;
575
576         /* verify user access to buffer */
577         if (!access_ok(VERIFY_WRITE, buf, nr)) {
578                 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
579                 "buffer\n", __FILE__, __LINE__);
580                 return -EFAULT;
581         }
582
583         add_wait_queue(&tty->read_wait, &wait);
584
585         for (;;) {
586                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
587                         ret = -EIO;
588                         break;
589                 }
590                 if (tty_hung_up_p(file))
591                         break;
592
593                 set_current_state(TASK_INTERRUPTIBLE);
594
595                 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
596                 if (rbuf) {
597                         if (rbuf->count > nr) {
598                                 /* too large for caller's buffer */
599                                 ret = -EOVERFLOW;
600                         } else {
601                                 __set_current_state(TASK_RUNNING);
602                                 if (copy_to_user(buf, rbuf->buf, rbuf->count))
603                                         ret = -EFAULT;
604                                 else
605                                         ret = rbuf->count;
606                         }
607
608                         if (n_hdlc->rx_free_buf_list.count >
609                             DEFAULT_RX_BUF_COUNT)
610                                 kfree(rbuf);
611                         else
612                                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
613                         break;
614                 }
615                         
616                 /* no data */
617                 if (tty_io_nonblock(tty, file)) {
618                         ret = -EAGAIN;
619                         break;
620                 }
621
622                 schedule();
623
624                 if (signal_pending(current)) {
625                         ret = -EINTR;
626                         break;
627                 }
628         }
629
630         remove_wait_queue(&tty->read_wait, &wait);
631         __set_current_state(TASK_RUNNING);
632
633         return ret;
634         
635 }       /* end of n_hdlc_tty_read() */
636
637 /**
638  * n_hdlc_tty_write - write a single frame of data to device
639  * @tty - pointer to associated tty device instance data
640  * @file - pointer to file object data
641  * @data - pointer to transmit data (one frame)
642  * @count - size of transmit frame in bytes
643  *              
644  * Returns the number of bytes written (or error code).
645  */
646 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
647                             const unsigned char *data, size_t count)
648 {
649         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
650         int error = 0;
651         DECLARE_WAITQUEUE(wait, current);
652         struct n_hdlc_buf *tbuf;
653
654         if (debuglevel >= DEBUG_LEVEL_INFO)     
655                 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
656                         __FILE__,__LINE__,count);
657                 
658         /* Verify pointers */
659         if (!n_hdlc)
660                 return -EIO;
661
662         if (n_hdlc->magic != HDLC_MAGIC)
663                 return -EIO;
664
665         /* verify frame size */
666         if (count > maxframe ) {
667                 if (debuglevel & DEBUG_LEVEL_INFO)
668                         printk (KERN_WARNING
669                                 "n_hdlc_tty_write: truncating user packet "
670                                 "from %lu to %d\n", (unsigned long) count,
671                                 maxframe );
672                 count = maxframe;
673         }
674         
675         add_wait_queue(&tty->write_wait, &wait);
676
677         for (;;) {
678                 set_current_state(TASK_INTERRUPTIBLE);
679         
680                 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
681                 if (tbuf)
682                         break;
683
684                 if (tty_io_nonblock(tty, file)) {
685                         error = -EAGAIN;
686                         break;
687                 }
688                 schedule();
689                         
690                 n_hdlc = tty2n_hdlc (tty);
691                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC || 
692                     tty != n_hdlc->tty) {
693                         printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
694                         error = -EIO;
695                         break;
696                 }
697                         
698                 if (signal_pending(current)) {
699                         error = -EINTR;
700                         break;
701                 }
702         }
703
704         __set_current_state(TASK_RUNNING);
705         remove_wait_queue(&tty->write_wait, &wait);
706
707         if (!error) {           
708                 /* Retrieve the user's buffer */
709                 memcpy(tbuf->buf, data, count);
710
711                 /* Send the data */
712                 tbuf->count = error = count;
713                 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
714                 n_hdlc_send_frames(n_hdlc,tty);
715         }
716
717         return error;
718         
719 }       /* end of n_hdlc_tty_write() */
720
721 /**
722  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
723  * @tty - pointer to tty instance data
724  * @file - pointer to open file object for device
725  * @cmd - IOCTL command code
726  * @arg - argument for IOCTL call (cmd dependent)
727  *
728  * Returns command dependent result.
729  */
730 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
731                             unsigned int cmd, unsigned long arg)
732 {
733         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
734         int error = 0;
735         int count;
736         unsigned long flags;
737         struct n_hdlc_buf *buf = NULL;
738
739         if (debuglevel >= DEBUG_LEVEL_INFO)     
740                 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
741                         __FILE__,__LINE__,cmd);
742                 
743         /* Verify the status of the device */
744         if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
745                 return -EBADF;
746
747         switch (cmd) {
748         case FIONREAD:
749                 /* report count of read data available */
750                 /* in next available frame (if any) */
751                 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
752                 buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
753                                                 struct n_hdlc_buf, list_item);
754                 if (buf)
755                         count = buf->count;
756                 else
757                         count = 0;
758                 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
759                 error = put_user(count, (int __user *)arg);
760                 break;
761
762         case TIOCOUTQ:
763                 /* get the pending tx byte count in the driver */
764                 count = tty_chars_in_buffer(tty);
765                 /* add size of next output frame in queue */
766                 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
767                 buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
768                                                 struct n_hdlc_buf, list_item);
769                 if (buf)
770                         count += buf->count;
771                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
772                 error = put_user(count, (int __user *)arg);
773                 break;
774
775         case TCFLSH:
776                 switch (arg) {
777                 case TCIOFLUSH:
778                 case TCOFLUSH:
779                         flush_tx_queue(tty);
780                 }
781                 /* fall through to default */
782
783         default:
784                 error = n_tty_ioctl_helper(tty, file, cmd, arg);
785                 break;
786         }
787         return error;
788         
789 }       /* end of n_hdlc_tty_ioctl() */
790
791 /**
792  * n_hdlc_tty_poll - TTY callback for poll system call
793  * @tty - pointer to tty instance data
794  * @filp - pointer to open file object for device
795  * @poll_table - wait queue for operations
796  * 
797  * Determine which operations (read/write) will not block and return info
798  * to caller.
799  * Returns a bit mask containing info on which ops will not block.
800  */
801 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
802                                     poll_table *wait)
803 {
804         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
805         unsigned int mask = 0;
806
807         if (debuglevel >= DEBUG_LEVEL_INFO)     
808                 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
809                 
810         if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
811                 /* queue current process into any wait queue that */
812                 /* may awaken in the future (read and write) */
813
814                 poll_wait(filp, &tty->read_wait, wait);
815                 poll_wait(filp, &tty->write_wait, wait);
816
817                 /* set bits for operations that won't block */
818                 if (!list_empty(&n_hdlc->rx_buf_list.list))
819                         mask |= POLLIN | POLLRDNORM;    /* readable */
820                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
821                         mask |= POLLHUP;
822                 if (tty_hung_up_p(filp))
823                         mask |= POLLHUP;
824                 if (!tty_is_writelocked(tty) &&
825                                 !list_empty(&n_hdlc->tx_free_buf_list.list))
826                         mask |= POLLOUT | POLLWRNORM;   /* writable */
827         }
828         return mask;
829 }       /* end of n_hdlc_tty_poll() */
830
831 /**
832  * n_hdlc_alloc - allocate an n_hdlc instance data structure
833  *
834  * Returns a pointer to newly created structure if success, otherwise %NULL
835  */
836 static struct n_hdlc *n_hdlc_alloc(void)
837 {
838         struct n_hdlc_buf *buf;
839         int i;
840         struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL);
841
842         if (!n_hdlc)
843                 return NULL;
844
845         spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);
846         spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
847         spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
848         spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
849
850         INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);
851         INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);
852         INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);
853         INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);
854
855         /* allocate free rx buffer list */
856         for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
857                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
858                 if (buf)
859                         n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
860                 else if (debuglevel >= DEBUG_LEVEL_INFO)        
861                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
862         }
863         
864         /* allocate free tx buffer list */
865         for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
866                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
867                 if (buf)
868                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
869                 else if (debuglevel >= DEBUG_LEVEL_INFO)        
870                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
871         }
872         
873         /* Initialize the control block */
874         n_hdlc->magic  = HDLC_MAGIC;
875         n_hdlc->flags  = 0;
876         
877         return n_hdlc;
878         
879 }       /* end of n_hdlc_alloc() */
880
881 /**
882  * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
883  * @buf_list - pointer to the buffer list
884  * @buf - pointer to the buffer
885  */
886 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
887                                                 struct n_hdlc_buf *buf)
888 {
889         unsigned long flags;
890
891         spin_lock_irqsave(&buf_list->spinlock, flags);
892
893         list_add(&buf->list_item, &buf_list->list);
894         buf_list->count++;
895
896         spin_unlock_irqrestore(&buf_list->spinlock, flags);
897 }
898
899 /**
900  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
901  * @buf_list - pointer to buffer list
902  * @buf - pointer to buffer
903  */
904 static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
905                            struct n_hdlc_buf *buf)
906 {
907         unsigned long flags;
908
909         spin_lock_irqsave(&buf_list->spinlock, flags);
910
911         list_add_tail(&buf->list_item, &buf_list->list);
912         buf_list->count++;
913
914         spin_unlock_irqrestore(&buf_list->spinlock, flags);
915 }       /* end of n_hdlc_buf_put() */
916
917 /**
918  * n_hdlc_buf_get - remove and return an HDLC buffer from list
919  * @buf_list - pointer to HDLC buffer list
920  * 
921  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
922  * list.
923  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
924  */
925 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
926 {
927         unsigned long flags;
928         struct n_hdlc_buf *buf;
929
930         spin_lock_irqsave(&buf_list->spinlock, flags);
931
932         buf = list_first_entry_or_null(&buf_list->list,
933                                                 struct n_hdlc_buf, list_item);
934         if (buf) {
935                 list_del(&buf->list_item);
936                 buf_list->count--;
937         }
938
939         spin_unlock_irqrestore(&buf_list->spinlock, flags);
940         return buf;
941 }       /* end of n_hdlc_buf_get() */
942
943 static char hdlc_banner[] __initdata =
944         KERN_INFO "HDLC line discipline maxframe=%u\n";
945 static char hdlc_register_ok[] __initdata =
946         KERN_INFO "N_HDLC line discipline registered.\n";
947 static char hdlc_register_fail[] __initdata =
948         KERN_ERR "error registering line discipline: %d\n";
949
950 static int __init n_hdlc_init(void)
951 {
952         int status;
953
954         /* range check maxframe arg */
955         if (maxframe < 4096)
956                 maxframe = 4096;
957         else if (maxframe > 65535)
958                 maxframe = 65535;
959
960         printk(hdlc_banner, maxframe);
961
962         status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
963         if (!status)
964                 printk(hdlc_register_ok);
965         else
966                 printk(hdlc_register_fail, status);
967
968         return status;
969         
970 }       /* end of init_module() */
971
972 static char hdlc_unregister_ok[] __exitdata =
973         KERN_INFO "N_HDLC: line discipline unregistered\n";
974 static char hdlc_unregister_fail[] __exitdata =
975         KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
976
977 static void __exit n_hdlc_exit(void)
978 {
979         /* Release tty registration of line discipline */
980         int status = tty_unregister_ldisc(N_HDLC);
981
982         if (status)
983                 printk(hdlc_unregister_fail, status);
984         else
985                 printk(hdlc_unregister_ok);
986 }
987
988 module_init(n_hdlc_init);
989 module_exit(n_hdlc_exit);
990
991 MODULE_LICENSE("GPL");
992 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
993 module_param(debuglevel, int, 0);
994 module_param(maxframe, int, 0);
995 MODULE_ALIAS_LDISC(N_HDLC);