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Merge branch 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[karo-tx-linux.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 <linux/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 n_hdlc_buf *link;
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 n_hdlc_buf *head;
126         struct n_hdlc_buf *tail;
127         int               count;
128         spinlock_t        spinlock;
129 };
130
131 /**
132  * struct n_hdlc - per device instance data structure
133  * @magic - magic value for structure
134  * @flags - miscellaneous control flags
135  * @tty - ptr to TTY structure
136  * @backup_tty - TTY to use if tty gets closed
137  * @tbusy - reentrancy flag for tx wakeup code
138  * @woke_up - FIXME: describe this field
139  * @tbuf - currently transmitting tx buffer
140  * @tx_buf_list - list of pending transmit frame buffers
141  * @rx_buf_list - list of received frame buffers
142  * @tx_free_buf_list - list unused transmit frame buffers
143  * @rx_free_buf_list - list unused received frame buffers
144  */
145 struct n_hdlc {
146         int                     magic;
147         __u32                   flags;
148         struct tty_struct       *tty;
149         struct tty_struct       *backup_tty;
150         int                     tbusy;
151         int                     woke_up;
152         struct n_hdlc_buf       *tbuf;
153         struct n_hdlc_buf_list  tx_buf_list;
154         struct n_hdlc_buf_list  rx_buf_list;
155         struct n_hdlc_buf_list  tx_free_buf_list;
156         struct n_hdlc_buf_list  rx_free_buf_list;
157 };
158
159 /*
160  * HDLC buffer list manipulation functions
161  */
162 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
163                            struct n_hdlc_buf *buf);
164 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
165
166 /* Local functions */
167
168 static struct n_hdlc *n_hdlc_alloc (void);
169
170 /* debug level can be set by insmod for debugging purposes */
171 #define DEBUG_LEVEL_INFO        1
172 static int debuglevel;
173
174 /* max frame size for memory allocations */
175 static int maxframe = 4096;
176
177 /* TTY callbacks */
178
179 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
180                            __u8 __user *buf, size_t nr);
181 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
182                             const unsigned char *buf, size_t nr);
183 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
184                             unsigned int cmd, unsigned long arg);
185 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
186                                     poll_table *wait);
187 static int n_hdlc_tty_open(struct tty_struct *tty);
188 static void n_hdlc_tty_close(struct tty_struct *tty);
189 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
190                                char *fp, int count);
191 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
192
193 #define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
194
195 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
196 #define n_hdlc2tty(n_hdlc)      ((n_hdlc)->tty)
197
198 static void flush_rx_queue(struct tty_struct *tty)
199 {
200         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
201         struct n_hdlc_buf *buf;
202
203         while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
204                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
205 }
206
207 static void flush_tx_queue(struct tty_struct *tty)
208 {
209         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
210         struct n_hdlc_buf *buf;
211         unsigned long flags;
212
213         while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
214                 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
215         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
216         if (n_hdlc->tbuf) {
217                 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, n_hdlc->tbuf);
218                 n_hdlc->tbuf = NULL;
219         }
220         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
221 }
222
223 static struct tty_ldisc_ops n_hdlc_ldisc = {
224         .owner          = THIS_MODULE,
225         .magic          = TTY_LDISC_MAGIC,
226         .name           = "hdlc",
227         .open           = n_hdlc_tty_open,
228         .close          = n_hdlc_tty_close,
229         .read           = n_hdlc_tty_read,
230         .write          = n_hdlc_tty_write,
231         .ioctl          = n_hdlc_tty_ioctl,
232         .poll           = n_hdlc_tty_poll,
233         .receive_buf    = n_hdlc_tty_receive,
234         .write_wakeup   = n_hdlc_tty_wakeup,
235         .flush_buffer   = flush_rx_queue,
236 };
237
238 /**
239  * n_hdlc_release - release an n_hdlc per device line discipline info structure
240  * @n_hdlc - per device line discipline info structure
241  */
242 static void n_hdlc_release(struct n_hdlc *n_hdlc)
243 {
244         struct tty_struct *tty = n_hdlc2tty (n_hdlc);
245         struct n_hdlc_buf *buf;
246         
247         if (debuglevel >= DEBUG_LEVEL_INFO)     
248                 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
249                 
250         /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
251         wake_up_interruptible (&tty->read_wait);
252         wake_up_interruptible (&tty->write_wait);
253
254         if (tty->disc_data == n_hdlc)
255                 tty->disc_data = NULL;  /* Break the tty->n_hdlc link */
256
257         /* Release transmit and receive buffers */
258         for(;;) {
259                 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
260                 if (buf) {
261                         kfree(buf);
262                 } else
263                         break;
264         }
265         for(;;) {
266                 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
267                 if (buf) {
268                         kfree(buf);
269                 } else
270                         break;
271         }
272         for(;;) {
273                 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
274                 if (buf) {
275                         kfree(buf);
276                 } else
277                         break;
278         }
279         for(;;) {
280                 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
281                 if (buf) {
282                         kfree(buf);
283                 } else
284                         break;
285         }
286         kfree(n_hdlc->tbuf);
287         kfree(n_hdlc);
288         
289 }       /* end of n_hdlc_release() */
290
291 /**
292  * n_hdlc_tty_close - line discipline close
293  * @tty - pointer to tty info structure
294  *
295  * Called when the line discipline is changed to something
296  * else, the tty is closed, or the tty detects a hangup.
297  */
298 static void n_hdlc_tty_close(struct tty_struct *tty)
299 {
300         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
301
302         if (debuglevel >= DEBUG_LEVEL_INFO)     
303                 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
304                 
305         if (n_hdlc != NULL) {
306                 if (n_hdlc->magic != HDLC_MAGIC) {
307                         printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
308                         return;
309                 }
310 #if defined(TTY_NO_WRITE_SPLIT)
311                 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
312 #endif
313                 tty->disc_data = NULL;
314                 if (tty == n_hdlc->backup_tty)
315                         n_hdlc->backup_tty = NULL;
316                 if (tty != n_hdlc->tty)
317                         return;
318                 if (n_hdlc->backup_tty) {
319                         n_hdlc->tty = n_hdlc->backup_tty;
320                 } else {
321                         n_hdlc_release (n_hdlc);
322                 }
323         }
324         
325         if (debuglevel >= DEBUG_LEVEL_INFO)     
326                 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
327                 
328 }       /* end of n_hdlc_tty_close() */
329
330 /**
331  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
332  * @tty - pointer to tty info structure
333  *
334  * Returns 0 if success, otherwise error code
335  */
336 static int n_hdlc_tty_open (struct tty_struct *tty)
337 {
338         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
339
340         if (debuglevel >= DEBUG_LEVEL_INFO)     
341                 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
342                 __FILE__,__LINE__,
343                 tty->name);
344                 
345         /* There should not be an existing table for this slot. */
346         if (n_hdlc) {
347                 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
348                 return -EEXIST;
349         }
350         
351         n_hdlc = n_hdlc_alloc();
352         if (!n_hdlc) {
353                 printk (KERN_ERR "n_hdlc_alloc failed\n");
354                 return -ENFILE;
355         }
356                 
357         tty->disc_data = n_hdlc;
358         n_hdlc->tty    = tty;
359         tty->receive_room = 65536;
360         
361 #if defined(TTY_NO_WRITE_SPLIT)
362         /* change tty_io write() to not split large writes into 8K chunks */
363         set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
364 #endif
365         
366         /* flush receive data from driver */
367         tty_driver_flush_buffer(tty);
368                 
369         if (debuglevel >= DEBUG_LEVEL_INFO)     
370                 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
371                 
372         return 0;
373         
374 }       /* end of n_tty_hdlc_open() */
375
376 /**
377  * n_hdlc_send_frames - send frames on pending send buffer list
378  * @n_hdlc - pointer to ldisc instance data
379  * @tty - pointer to tty instance data
380  *
381  * Send frames on pending send buffer list until the driver does not accept a
382  * frame (busy) this function is called after adding a frame to the send buffer
383  * list and by the tty wakeup callback.
384  */
385 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
386 {
387         register int actual;
388         unsigned long flags;
389         struct n_hdlc_buf *tbuf;
390
391         if (debuglevel >= DEBUG_LEVEL_INFO)     
392                 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
393  check_again:
394                 
395         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
396         if (n_hdlc->tbusy) {
397                 n_hdlc->woke_up = 1;
398                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
399                 return;
400         }
401         n_hdlc->tbusy = 1;
402         n_hdlc->woke_up = 0;
403         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
404
405         /* get current transmit buffer or get new transmit */
406         /* buffer from list of pending transmit buffers */
407                 
408         tbuf = n_hdlc->tbuf;
409         if (!tbuf)
410                 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
411                 
412         while (tbuf) {
413                 if (debuglevel >= DEBUG_LEVEL_INFO)     
414                         printk("%s(%d)sending frame %p, count=%d\n",
415                                 __FILE__,__LINE__,tbuf,tbuf->count);
416                         
417                 /* Send the next block of data to device */
418                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
419                 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
420
421                 /* rollback was possible and has been done */
422                 if (actual == -ERESTARTSYS) {
423                         n_hdlc->tbuf = tbuf;
424                         break;
425                 }
426                 /* if transmit error, throw frame away by */
427                 /* pretending it was accepted by driver */
428                 if (actual < 0)
429                         actual = tbuf->count;
430                 
431                 if (actual == tbuf->count) {
432                         if (debuglevel >= DEBUG_LEVEL_INFO)     
433                                 printk("%s(%d)frame %p completed\n",
434                                         __FILE__,__LINE__,tbuf);
435                                         
436                         /* free current transmit buffer */
437                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
438                         
439                         /* this tx buffer is done */
440                         n_hdlc->tbuf = NULL;
441                         
442                         /* wait up sleeping writers */
443                         wake_up_interruptible(&tty->write_wait);
444         
445                         /* get next pending transmit buffer */
446                         tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
447                 } else {
448                         if (debuglevel >= DEBUG_LEVEL_INFO)     
449                                 printk("%s(%d)frame %p pending\n",
450                                         __FILE__,__LINE__,tbuf);
451                                         
452                         /* buffer not accepted by driver */
453                         /* set this buffer as pending buffer */
454                         n_hdlc->tbuf = tbuf;
455                         break;
456                 }
457         }
458         
459         if (!tbuf)
460                 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
461         
462         /* Clear the re-entry flag */
463         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
464         n_hdlc->tbusy = 0;
465         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 
466         
467         if (n_hdlc->woke_up)
468           goto check_again;
469
470         if (debuglevel >= DEBUG_LEVEL_INFO)     
471                 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
472                 
473 }       /* end of n_hdlc_send_frames() */
474
475 /**
476  * n_hdlc_tty_wakeup - Callback for transmit wakeup
477  * @tty - pointer to associated tty instance data
478  *
479  * Called when low level device driver can accept more send data.
480  */
481 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
482 {
483         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
484
485         if (debuglevel >= DEBUG_LEVEL_INFO)     
486                 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
487                 
488         if (!n_hdlc)
489                 return;
490
491         if (tty != n_hdlc->tty) {
492                 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
493                 return;
494         }
495
496         n_hdlc_send_frames (n_hdlc, tty);
497                 
498 }       /* end of n_hdlc_tty_wakeup() */
499
500 /**
501  * n_hdlc_tty_receive - Called by tty driver when receive data is available
502  * @tty - pointer to tty instance data
503  * @data - pointer to received data
504  * @flags - pointer to flags for data
505  * @count - count of received data in bytes
506  *
507  * Called by tty low level driver when receive data is available. Data is
508  * interpreted as one HDLC frame.
509  */
510 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
511                                char *flags, int count)
512 {
513         register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
514         register struct n_hdlc_buf *buf;
515
516         if (debuglevel >= DEBUG_LEVEL_INFO)     
517                 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
518                         __FILE__,__LINE__, count);
519                 
520         /* This can happen if stuff comes in on the backup tty */
521         if (!n_hdlc || tty != n_hdlc->tty)
522                 return;
523                 
524         /* verify line is using HDLC discipline */
525         if (n_hdlc->magic != HDLC_MAGIC) {
526                 printk("%s(%d) line not using HDLC discipline\n",
527                         __FILE__,__LINE__);
528                 return;
529         }
530         
531         if ( count>maxframe ) {
532                 if (debuglevel >= DEBUG_LEVEL_INFO)     
533                         printk("%s(%d) rx count>maxframesize, data discarded\n",
534                                __FILE__,__LINE__);
535                 return;
536         }
537
538         /* get a free HDLC buffer */    
539         buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
540         if (!buf) {
541                 /* no buffers in free list, attempt to allocate another rx buffer */
542                 /* unless the maximum count has been reached */
543                 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
544                         buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
545         }
546         
547         if (!buf) {
548                 if (debuglevel >= DEBUG_LEVEL_INFO)     
549                         printk("%s(%d) no more rx buffers, data discarded\n",
550                                __FILE__,__LINE__);
551                 return;
552         }
553                 
554         /* copy received data to HDLC buffer */
555         memcpy(buf->buf,data,count);
556         buf->count=count;
557
558         /* add HDLC buffer to list of received frames */
559         n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
560         
561         /* wake up any blocked reads and perform async signalling */
562         wake_up_interruptible (&tty->read_wait);
563         if (n_hdlc->tty->fasync != NULL)
564                 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
565
566 }       /* end of n_hdlc_tty_receive() */
567
568 /**
569  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
570  * @tty - pointer to tty instance data
571  * @file - pointer to open file object
572  * @buf - pointer to returned data buffer
573  * @nr - size of returned data buffer
574  *      
575  * Returns the number of bytes returned or error code.
576  */
577 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
578                            __u8 __user *buf, size_t nr)
579 {
580         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
581         int ret = 0;
582         struct n_hdlc_buf *rbuf;
583         DECLARE_WAITQUEUE(wait, current);
584
585         if (debuglevel >= DEBUG_LEVEL_INFO)     
586                 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
587                 
588         /* Validate the pointers */
589         if (!n_hdlc)
590                 return -EIO;
591
592         /* verify user access to buffer */
593         if (!access_ok(VERIFY_WRITE, buf, nr)) {
594                 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
595                 "buffer\n", __FILE__, __LINE__);
596                 return -EFAULT;
597         }
598
599         add_wait_queue(&tty->read_wait, &wait);
600
601         for (;;) {
602                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
603                         ret = -EIO;
604                         break;
605                 }
606                 if (tty_hung_up_p(file))
607                         break;
608
609                 set_current_state(TASK_INTERRUPTIBLE);
610
611                 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
612                 if (rbuf) {
613                         if (rbuf->count > nr) {
614                                 /* too large for caller's buffer */
615                                 ret = -EOVERFLOW;
616                         } else {
617                                 if (copy_to_user(buf, rbuf->buf, rbuf->count))
618                                         ret = -EFAULT;
619                                 else
620                                         ret = rbuf->count;
621                         }
622
623                         if (n_hdlc->rx_free_buf_list.count >
624                             DEFAULT_RX_BUF_COUNT)
625                                 kfree(rbuf);
626                         else
627                                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
628                         break;
629                 }
630                         
631                 /* no data */
632                 if (file->f_flags & O_NONBLOCK) {
633                         ret = -EAGAIN;
634                         break;
635                 }
636
637                 schedule();
638
639                 if (signal_pending(current)) {
640                         ret = -EINTR;
641                         break;
642                 }
643         }
644
645         remove_wait_queue(&tty->read_wait, &wait);
646         __set_current_state(TASK_RUNNING);
647
648         return ret;
649         
650 }       /* end of n_hdlc_tty_read() */
651
652 /**
653  * n_hdlc_tty_write - write a single frame of data to device
654  * @tty - pointer to associated tty device instance data
655  * @file - pointer to file object data
656  * @data - pointer to transmit data (one frame)
657  * @count - size of transmit frame in bytes
658  *              
659  * Returns the number of bytes written (or error code).
660  */
661 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
662                             const unsigned char *data, size_t count)
663 {
664         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
665         int error = 0;
666         DECLARE_WAITQUEUE(wait, current);
667         struct n_hdlc_buf *tbuf;
668
669         if (debuglevel >= DEBUG_LEVEL_INFO)     
670                 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
671                         __FILE__,__LINE__,count);
672                 
673         /* Verify pointers */
674         if (!n_hdlc)
675                 return -EIO;
676
677         if (n_hdlc->magic != HDLC_MAGIC)
678                 return -EIO;
679
680         /* verify frame size */
681         if (count > maxframe ) {
682                 if (debuglevel & DEBUG_LEVEL_INFO)
683                         printk (KERN_WARNING
684                                 "n_hdlc_tty_write: truncating user packet "
685                                 "from %lu to %d\n", (unsigned long) count,
686                                 maxframe );
687                 count = maxframe;
688         }
689         
690         add_wait_queue(&tty->write_wait, &wait);
691
692         for (;;) {
693                 set_current_state(TASK_INTERRUPTIBLE);
694         
695                 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
696                 if (tbuf)
697                         break;
698
699                 if (file->f_flags & O_NONBLOCK) {
700                         error = -EAGAIN;
701                         break;
702                 }
703                 schedule();
704                         
705                 n_hdlc = tty2n_hdlc (tty);
706                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC || 
707                     tty != n_hdlc->tty) {
708                         printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
709                         error = -EIO;
710                         break;
711                 }
712                         
713                 if (signal_pending(current)) {
714                         error = -EINTR;
715                         break;
716                 }
717         }
718
719         __set_current_state(TASK_RUNNING);
720         remove_wait_queue(&tty->write_wait, &wait);
721
722         if (!error) {           
723                 /* Retrieve the user's buffer */
724                 memcpy(tbuf->buf, data, count);
725
726                 /* Send the data */
727                 tbuf->count = error = count;
728                 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
729                 n_hdlc_send_frames(n_hdlc,tty);
730         }
731
732         return error;
733         
734 }       /* end of n_hdlc_tty_write() */
735
736 /**
737  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
738  * @tty - pointer to tty instance data
739  * @file - pointer to open file object for device
740  * @cmd - IOCTL command code
741  * @arg - argument for IOCTL call (cmd dependent)
742  *
743  * Returns command dependent result.
744  */
745 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
746                             unsigned int cmd, unsigned long arg)
747 {
748         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
749         int error = 0;
750         int count;
751         unsigned long flags;
752         
753         if (debuglevel >= DEBUG_LEVEL_INFO)     
754                 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
755                         __FILE__,__LINE__,cmd);
756                 
757         /* Verify the status of the device */
758         if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
759                 return -EBADF;
760
761         switch (cmd) {
762         case FIONREAD:
763                 /* report count of read data available */
764                 /* in next available frame (if any) */
765                 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
766                 if (n_hdlc->rx_buf_list.head)
767                         count = n_hdlc->rx_buf_list.head->count;
768                 else
769                         count = 0;
770                 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
771                 error = put_user(count, (int __user *)arg);
772                 break;
773
774         case TIOCOUTQ:
775                 /* get the pending tx byte count in the driver */
776                 count = tty_chars_in_buffer(tty);
777                 /* add size of next output frame in queue */
778                 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
779                 if (n_hdlc->tx_buf_list.head)
780                         count += n_hdlc->tx_buf_list.head->count;
781                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
782                 error = put_user(count, (int __user *)arg);
783                 break;
784
785         case TCFLSH:
786                 switch (arg) {
787                 case TCIOFLUSH:
788                 case TCOFLUSH:
789                         flush_tx_queue(tty);
790                 }
791                 /* fall through to default */
792
793         default:
794                 error = n_tty_ioctl_helper(tty, file, cmd, arg);
795                 break;
796         }
797         return error;
798         
799 }       /* end of n_hdlc_tty_ioctl() */
800
801 /**
802  * n_hdlc_tty_poll - TTY callback for poll system call
803  * @tty - pointer to tty instance data
804  * @filp - pointer to open file object for device
805  * @poll_table - wait queue for operations
806  * 
807  * Determine which operations (read/write) will not block and return info
808  * to caller.
809  * Returns a bit mask containing info on which ops will not block.
810  */
811 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
812                                     poll_table *wait)
813 {
814         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
815         unsigned int mask = 0;
816
817         if (debuglevel >= DEBUG_LEVEL_INFO)     
818                 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
819                 
820         if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
821                 /* queue current process into any wait queue that */
822                 /* may awaken in the future (read and write) */
823
824                 poll_wait(filp, &tty->read_wait, wait);
825                 poll_wait(filp, &tty->write_wait, wait);
826
827                 /* set bits for operations that won't block */
828                 if (n_hdlc->rx_buf_list.head)
829                         mask |= POLLIN | POLLRDNORM;    /* readable */
830                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
831                         mask |= POLLHUP;
832                 if (tty_hung_up_p(filp))
833                         mask |= POLLHUP;
834                 if (!tty_is_writelocked(tty) &&
835                                 n_hdlc->tx_free_buf_list.head)
836                         mask |= POLLOUT | POLLWRNORM;   /* writable */
837         }
838         return mask;
839 }       /* end of n_hdlc_tty_poll() */
840
841 /**
842  * n_hdlc_alloc - allocate an n_hdlc instance data structure
843  *
844  * Returns a pointer to newly created structure if success, otherwise %NULL
845  */
846 static struct n_hdlc *n_hdlc_alloc(void)
847 {
848         struct n_hdlc_buf *buf;
849         int i;
850         struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL);
851
852         if (!n_hdlc)
853                 return NULL;
854
855         spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);
856         spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
857         spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
858         spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
859         
860         /* allocate free rx buffer list */
861         for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
862                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
863                 if (buf)
864                         n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
865                 else if (debuglevel >= DEBUG_LEVEL_INFO)        
866                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
867         }
868         
869         /* allocate free tx buffer list */
870         for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
871                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
872                 if (buf)
873                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
874                 else if (debuglevel >= DEBUG_LEVEL_INFO)        
875                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
876         }
877         
878         /* Initialize the control block */
879         n_hdlc->magic  = HDLC_MAGIC;
880         n_hdlc->flags  = 0;
881         
882         return n_hdlc;
883         
884 }       /* end of n_hdlc_alloc() */
885
886 /**
887  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
888  * @list - pointer to buffer list
889  * @buf - pointer to buffer
890  */
891 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
892                            struct n_hdlc_buf *buf)
893 {
894         unsigned long flags;
895         spin_lock_irqsave(&list->spinlock,flags);
896         
897         buf->link=NULL;
898         if (list->tail)
899                 list->tail->link = buf;
900         else
901                 list->head = buf;
902         list->tail = buf;
903         (list->count)++;
904         
905         spin_unlock_irqrestore(&list->spinlock,flags);
906         
907 }       /* end of n_hdlc_buf_put() */
908
909 /**
910  * n_hdlc_buf_get - remove and return an HDLC buffer from list
911  * @list - pointer to HDLC buffer list
912  * 
913  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
914  * list.
915  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
916  */
917 static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
918 {
919         unsigned long flags;
920         struct n_hdlc_buf *buf;
921         spin_lock_irqsave(&list->spinlock,flags);
922         
923         buf = list->head;
924         if (buf) {
925                 list->head = buf->link;
926                 (list->count)--;
927         }
928         if (!list->head)
929                 list->tail = NULL;
930         
931         spin_unlock_irqrestore(&list->spinlock,flags);
932         return buf;
933         
934 }       /* end of n_hdlc_buf_get() */
935
936 static char hdlc_banner[] __initdata =
937         KERN_INFO "HDLC line discipline maxframe=%u\n";
938 static char hdlc_register_ok[] __initdata =
939         KERN_INFO "N_HDLC line discipline registered.\n";
940 static char hdlc_register_fail[] __initdata =
941         KERN_ERR "error registering line discipline: %d\n";
942
943 static int __init n_hdlc_init(void)
944 {
945         int status;
946
947         /* range check maxframe arg */
948         if (maxframe < 4096)
949                 maxframe = 4096;
950         else if (maxframe > 65535)
951                 maxframe = 65535;
952
953         printk(hdlc_banner, maxframe);
954
955         status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
956         if (!status)
957                 printk(hdlc_register_ok);
958         else
959                 printk(hdlc_register_fail, status);
960
961         return status;
962         
963 }       /* end of init_module() */
964
965 static char hdlc_unregister_ok[] __exitdata =
966         KERN_INFO "N_HDLC: line discipline unregistered\n";
967 static char hdlc_unregister_fail[] __exitdata =
968         KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
969
970 static void __exit n_hdlc_exit(void)
971 {
972         /* Release tty registration of line discipline */
973         int status = tty_unregister_ldisc(N_HDLC);
974
975         if (status)
976                 printk(hdlc_unregister_fail, status);
977         else
978                 printk(hdlc_unregister_ok);
979 }
980
981 module_init(n_hdlc_init);
982 module_exit(n_hdlc_exit);
983
984 MODULE_LICENSE("GPL");
985 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
986 module_param(debuglevel, int, 0);
987 module_param(maxframe, int, 0);
988 MODULE_ALIAS_LDISC(N_HDLC);