Update Yoichi Yuasa's email address.
[linux-2.6] / drivers / char / 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  * $Id: n_hdlc.c,v 4.8 2003/05/06 21:18:51 paulkf Exp $
14  *
15  * This code is released under the GNU General Public License (GPL)
16  *
17  * This module implements the tty line discipline N_HDLC for use with
18  * tty device drivers that support bit-synchronous HDLC communications.
19  *
20  * All HDLC data is frame oriented which means:
21  *
22  * 1. tty write calls represent one complete transmit frame of data
23  *    The device driver should accept the complete frame or none of 
24  *    the frame (busy) in the write method. Each write call should have
25  *    a byte count in the range of 2-65535 bytes (2 is min HDLC frame
26  *    with 1 addr byte and 1 ctrl byte). The max byte count of 65535
27  *    should include any crc bytes required. For example, when using
28  *    CCITT CRC32, 4 crc bytes are required, so the maximum size frame
29  *    the application may transmit is limited to 65531 bytes. For CCITT
30  *    CRC16, the maximum application frame size would be 65533.
31  *
32  *
33  * 2. receive callbacks from the device driver represents
34  *    one received frame. The device driver should bypass
35  *    the tty flip buffer and call the line discipline receive
36  *    callback directly to avoid fragmenting or concatenating
37  *    multiple frames into a single receive callback.
38  *
39  *    The HDLC line discipline queues the receive frames in separate
40  *    buffers so complete receive frames can be returned by the
41  *    tty read calls.
42  *
43  * 3. tty read calls returns an entire frame of data or nothing.
44  *    
45  * 4. all send and receive data is considered raw. No processing
46  *    or translation is performed by the line discipline, regardless
47  *    of the tty flags
48  *
49  * 5. When line discipline is queried for the amount of receive
50  *    data available (FIOC), 0 is returned if no data available,
51  *    otherwise the count of the next available frame is returned.
52  *    (instead of the sum of all received frame counts).
53  *
54  * These conventions allow the standard tty programming interface
55  * to be used for synchronous HDLC applications when used with
56  * this line discipline (or another line discipline that is frame
57  * oriented such as N_PPP).
58  *
59  * The SyncLink driver (synclink.c) implements both asynchronous
60  * (using standard line discipline N_TTY) and synchronous HDLC
61  * (using N_HDLC) communications, with the latter using the above
62  * conventions.
63  *
64  * This implementation is very basic and does not maintain
65  * any statistics. The main point is to enforce the raw data
66  * and frame orientation of HDLC communications.
67  *
68  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
69  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
70  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
71  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
72  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
73  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
74  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
75  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
76  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
77  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
78  * OF THE POSSIBILITY OF SUCH DAMAGE.
79  */
80
81 #define HDLC_MAGIC 0x239e
82 #define HDLC_VERSION "$Revision: 4.8 $"
83
84 #include <linux/config.h>
85 #include <linux/module.h>
86 #include <linux/init.h>
87 #include <linux/kernel.h>
88 #include <linux/sched.h>
89 #include <linux/types.h>
90 #include <linux/fcntl.h>
91 #include <linux/interrupt.h>
92 #include <linux/ptrace.h>
93
94 #undef VERSION
95 #define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
96
97 #include <linux/poll.h>
98 #include <linux/in.h>
99 #include <linux/ioctl.h>
100 #include <linux/slab.h>
101 #include <linux/tty.h>
102 #include <linux/errno.h>
103 #include <linux/string.h>       /* used in new tty drivers */
104 #include <linux/signal.h>       /* used in new tty drivers */
105 #include <linux/if.h>
106 #include <linux/bitops.h>
107
108 #include <asm/system.h>
109 #include <asm/termios.h>
110 #include <asm/uaccess.h>
111
112 /*
113  * Buffers for individual HDLC frames
114  */
115 #define MAX_HDLC_FRAME_SIZE 65535 
116 #define DEFAULT_RX_BUF_COUNT 10
117 #define MAX_RX_BUF_COUNT 60
118 #define DEFAULT_TX_BUF_COUNT 1
119
120 struct n_hdlc_buf {
121         struct n_hdlc_buf *link;
122         int               count;
123         char              buf[1];
124 };
125
126 #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
127
128 struct n_hdlc_buf_list {
129         struct n_hdlc_buf *head;
130         struct n_hdlc_buf *tail;
131         int               count;
132         spinlock_t        spinlock;
133 };
134
135 /**
136  * struct n_hdlc - per device instance data structure
137  * @magic - magic value for structure
138  * @flags - miscellaneous control flags
139  * @tty - ptr to TTY structure
140  * @backup_tty - TTY to use if tty gets closed
141  * @tbusy - reentrancy flag for tx wakeup code
142  * @woke_up - FIXME: describe this field
143  * @tbuf - currently transmitting tx buffer
144  * @tx_buf_list - list of pending transmit frame buffers
145  * @rx_buf_list - list of received frame buffers
146  * @tx_free_buf_list - list unused transmit frame buffers
147  * @rx_free_buf_list - list unused received frame buffers
148  */
149 struct n_hdlc {
150         int                     magic;
151         __u32                   flags;
152         struct tty_struct       *tty;
153         struct tty_struct       *backup_tty;
154         int                     tbusy;
155         int                     woke_up;
156         struct n_hdlc_buf       *tbuf;
157         struct n_hdlc_buf_list  tx_buf_list;
158         struct n_hdlc_buf_list  rx_buf_list;
159         struct n_hdlc_buf_list  tx_free_buf_list;
160         struct n_hdlc_buf_list  rx_free_buf_list;
161 };
162
163 /*
164  * HDLC buffer list manipulation functions
165  */
166 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list);
167 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
168                            struct n_hdlc_buf *buf);
169 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
170
171 /* Local functions */
172
173 static struct n_hdlc *n_hdlc_alloc (void);
174
175 /* debug level can be set by insmod for debugging purposes */
176 #define DEBUG_LEVEL_INFO        1
177 static int debuglevel;
178
179 /* max frame size for memory allocations */
180 static int maxframe = 4096;
181
182 /* TTY callbacks */
183
184 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
185                            __u8 __user *buf, size_t nr);
186 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
187                             const unsigned char *buf, size_t nr);
188 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
189                             unsigned int cmd, unsigned long arg);
190 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
191                                     poll_table *wait);
192 static int n_hdlc_tty_open(struct tty_struct *tty);
193 static void n_hdlc_tty_close(struct tty_struct *tty);
194 static int n_hdlc_tty_room(struct tty_struct *tty);
195 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
196                                char *fp, int count);
197 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
198
199 #define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
200
201 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
202 #define n_hdlc2tty(n_hdlc)      ((n_hdlc)->tty)
203
204 static struct tty_ldisc n_hdlc_ldisc = {
205         .owner          = THIS_MODULE,
206         .magic          = TTY_LDISC_MAGIC,
207         .name           = "hdlc",
208         .open           = n_hdlc_tty_open,
209         .close          = n_hdlc_tty_close,
210         .read           = n_hdlc_tty_read,
211         .write          = n_hdlc_tty_write,
212         .ioctl          = n_hdlc_tty_ioctl,
213         .poll           = n_hdlc_tty_poll,
214         .receive_buf    = n_hdlc_tty_receive,
215         .receive_room   = n_hdlc_tty_room,
216         .write_wakeup   = n_hdlc_tty_wakeup,
217 };
218
219 /**
220  * n_hdlc_release - release an n_hdlc per device line discipline info structure
221  * @n_hdlc - per device line discipline info structure
222  */
223 static void n_hdlc_release(struct n_hdlc *n_hdlc)
224 {
225         struct tty_struct *tty = n_hdlc2tty (n_hdlc);
226         struct n_hdlc_buf *buf;
227         
228         if (debuglevel >= DEBUG_LEVEL_INFO)     
229                 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
230                 
231         /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
232         wake_up_interruptible (&tty->read_wait);
233         wake_up_interruptible (&tty->write_wait);
234
235         if (tty != NULL && tty->disc_data == n_hdlc)
236                 tty->disc_data = NULL;  /* Break the tty->n_hdlc link */
237
238         /* Release transmit and receive buffers */
239         for(;;) {
240                 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
241                 if (buf) {
242                         kfree(buf);
243                 } else
244                         break;
245         }
246         for(;;) {
247                 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
248                 if (buf) {
249                         kfree(buf);
250                 } else
251                         break;
252         }
253         for(;;) {
254                 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
255                 if (buf) {
256                         kfree(buf);
257                 } else
258                         break;
259         }
260         for(;;) {
261                 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
262                 if (buf) {
263                         kfree(buf);
264                 } else
265                         break;
266         }
267         kfree(n_hdlc->tbuf);
268         kfree(n_hdlc);
269         
270 }       /* end of n_hdlc_release() */
271
272 /**
273  * n_hdlc_tty_close - line discipline close
274  * @tty - pointer to tty info structure
275  *
276  * Called when the line discipline is changed to something
277  * else, the tty is closed, or the tty detects a hangup.
278  */
279 static void n_hdlc_tty_close(struct tty_struct *tty)
280 {
281         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
282
283         if (debuglevel >= DEBUG_LEVEL_INFO)     
284                 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
285                 
286         if (n_hdlc != NULL) {
287                 if (n_hdlc->magic != HDLC_MAGIC) {
288                         printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
289                         return;
290                 }
291 #if defined(TTY_NO_WRITE_SPLIT)
292                 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
293 #endif
294                 tty->disc_data = NULL;
295                 if (tty == n_hdlc->backup_tty)
296                         n_hdlc->backup_tty = NULL;
297                 if (tty != n_hdlc->tty)
298                         return;
299                 if (n_hdlc->backup_tty) {
300                         n_hdlc->tty = n_hdlc->backup_tty;
301                 } else {
302                         n_hdlc_release (n_hdlc);
303                 }
304         }
305         
306         if (debuglevel >= DEBUG_LEVEL_INFO)     
307                 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
308                 
309 }       /* end of n_hdlc_tty_close() */
310
311 /**
312  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
313  * @tty - pointer to tty info structure
314  *
315  * Returns 0 if success, otherwise error code
316  */
317 static int n_hdlc_tty_open (struct tty_struct *tty)
318 {
319         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
320
321         if (debuglevel >= DEBUG_LEVEL_INFO)     
322                 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
323                 __FILE__,__LINE__,
324                 tty->name);
325                 
326         /* There should not be an existing table for this slot. */
327         if (n_hdlc) {
328                 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
329                 return -EEXIST;
330         }
331         
332         n_hdlc = n_hdlc_alloc();
333         if (!n_hdlc) {
334                 printk (KERN_ERR "n_hdlc_alloc failed\n");
335                 return -ENFILE;
336         }
337                 
338         tty->disc_data = n_hdlc;
339         n_hdlc->tty    = tty;
340         
341 #if defined(TTY_NO_WRITE_SPLIT)
342         /* change tty_io write() to not split large writes into 8K chunks */
343         set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
344 #endif
345         
346         /* Flush any pending characters in the driver and discipline. */
347         
348         if (tty->ldisc.flush_buffer)
349                 tty->ldisc.flush_buffer (tty);
350
351         if (tty->driver->flush_buffer)
352                 tty->driver->flush_buffer (tty);
353                 
354         if (debuglevel >= DEBUG_LEVEL_INFO)     
355                 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
356                 
357         return 0;
358         
359 }       /* end of n_tty_hdlc_open() */
360
361 /**
362  * n_hdlc_send_frames - send frames on pending send buffer list
363  * @n_hdlc - pointer to ldisc instance data
364  * @tty - pointer to tty instance data
365  *
366  * Send frames on pending send buffer list until the driver does not accept a
367  * frame (busy) this function is called after adding a frame to the send buffer
368  * list and by the tty wakeup callback.
369  */
370 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
371 {
372         register int actual;
373         unsigned long flags;
374         struct n_hdlc_buf *tbuf;
375
376         if (debuglevel >= DEBUG_LEVEL_INFO)     
377                 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
378  check_again:
379                 
380         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
381         if (n_hdlc->tbusy) {
382                 n_hdlc->woke_up = 1;
383                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
384                 return;
385         }
386         n_hdlc->tbusy = 1;
387         n_hdlc->woke_up = 0;
388         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
389
390         /* get current transmit buffer or get new transmit */
391         /* buffer from list of pending transmit buffers */
392                 
393         tbuf = n_hdlc->tbuf;
394         if (!tbuf)
395                 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
396                 
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                 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
404                 actual = tty->driver->write(tty, tbuf->buf, tbuf->count);
405                     
406                 /* if transmit error, throw frame away by */
407                 /* pretending it was accepted by driver */
408                 if (actual < 0)
409                         actual = tbuf->count;
410                 
411                 if (actual == tbuf->count) {
412                         if (debuglevel >= DEBUG_LEVEL_INFO)     
413                                 printk("%s(%d)frame %p completed\n",
414                                         __FILE__,__LINE__,tbuf);
415                                         
416                         /* free current transmit buffer */
417                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
418                         
419                         /* this tx buffer is done */
420                         n_hdlc->tbuf = NULL;
421                         
422                         /* wait up sleeping writers */
423                         wake_up_interruptible(&tty->write_wait);
424         
425                         /* get next pending transmit buffer */
426                         tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
427                 } else {
428                         if (debuglevel >= DEBUG_LEVEL_INFO)     
429                                 printk("%s(%d)frame %p pending\n",
430                                         __FILE__,__LINE__,tbuf);
431                                         
432                         /* buffer not accepted by driver */
433                         /* set this buffer as pending buffer */
434                         n_hdlc->tbuf = tbuf;
435                         break;
436                 }
437         }
438         
439         if (!tbuf)
440                 tty->flags  &= ~(1 << TTY_DO_WRITE_WAKEUP);
441         
442         /* Clear the re-entry flag */
443         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
444         n_hdlc->tbusy = 0;
445         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 
446         
447         if (n_hdlc->woke_up)
448           goto check_again;
449
450         if (debuglevel >= DEBUG_LEVEL_INFO)     
451                 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
452                 
453 }       /* end of n_hdlc_send_frames() */
454
455 /**
456  * n_hdlc_tty_wakeup - Callback for transmit wakeup
457  * @tty - pointer to associated tty instance data
458  *
459  * Called when low level device driver can accept more send data.
460  */
461 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
462 {
463         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
464
465         if (debuglevel >= DEBUG_LEVEL_INFO)     
466                 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
467                 
468         if (!n_hdlc)
469                 return;
470
471         if (tty != n_hdlc->tty) {
472                 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
473                 return;
474         }
475
476         n_hdlc_send_frames (n_hdlc, tty);
477                 
478 }       /* end of n_hdlc_tty_wakeup() */
479
480 /**
481  * n_hdlc_tty_room - Return the amount of space left in the receiver's buffer
482  * @tty - pointer to associated tty instance data
483  *
484  * Callback function from tty driver. Return the amount of space left in the
485  * receiver's buffer to decide if remote transmitter is to be throttled.
486  */
487 static int n_hdlc_tty_room(struct tty_struct *tty)
488 {
489         if (debuglevel >= DEBUG_LEVEL_INFO)     
490                 printk("%s(%d)n_hdlc_tty_room() called\n",__FILE__,__LINE__);
491         /* always return a larger number to prevent */
492         /* throttling of remote transmitter. */
493         return 65536;
494 }       /* end of n_hdlc_tty_root() */
495
496 /**
497  * n_hdlc_tty_receive - Called by tty driver when receive data is available
498  * @tty - pointer to tty instance data
499  * @data - pointer to received data
500  * @flags - pointer to flags for data
501  * @count - count of received data in bytes
502  *
503  * Called by tty low level driver when receive data is available. Data is
504  * interpreted as one HDLC frame.
505  */
506 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
507                                char *flags, int count)
508 {
509         register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
510         register struct n_hdlc_buf *buf;
511
512         if (debuglevel >= DEBUG_LEVEL_INFO)     
513                 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
514                         __FILE__,__LINE__, count);
515                 
516         /* This can happen if stuff comes in on the backup tty */
517         if (n_hdlc == 0 || tty != n_hdlc->tty)
518                 return;
519                 
520         /* verify line is using HDLC discipline */
521         if (n_hdlc->magic != HDLC_MAGIC) {
522                 printk("%s(%d) line not using HDLC discipline\n",
523                         __FILE__,__LINE__);
524                 return;
525         }
526         
527         if ( count>maxframe ) {
528                 if (debuglevel >= DEBUG_LEVEL_INFO)     
529                         printk("%s(%d) rx count>maxframesize, data discarded\n",
530                                __FILE__,__LINE__);
531                 return;
532         }
533
534         /* get a free HDLC buffer */    
535         buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
536         if (!buf) {
537                 /* no buffers in free list, attempt to allocate another rx buffer */
538                 /* unless the maximum count has been reached */
539                 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
540                         buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
541         }
542         
543         if (!buf) {
544                 if (debuglevel >= DEBUG_LEVEL_INFO)     
545                         printk("%s(%d) no more rx buffers, data discarded\n",
546                                __FILE__,__LINE__);
547                 return;
548         }
549                 
550         /* copy received data to HDLC buffer */
551         memcpy(buf->buf,data,count);
552         buf->count=count;
553
554         /* add HDLC buffer to list of received frames */
555         n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
556         
557         /* wake up any blocked reads and perform async signalling */
558         wake_up_interruptible (&tty->read_wait);
559         if (n_hdlc->tty->fasync != NULL)
560                 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
561
562 }       /* end of n_hdlc_tty_receive() */
563
564 /**
565  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
566  * @tty - pointer to tty instance data
567  * @file - pointer to open file object
568  * @buf - pointer to returned data buffer
569  * @nr - size of returned data buffer
570  *      
571  * Returns the number of bytes returned or error code.
572  */
573 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
574                            __u8 __user *buf, size_t nr)
575 {
576         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
577         int ret;
578         struct n_hdlc_buf *rbuf;
579
580         if (debuglevel >= DEBUG_LEVEL_INFO)     
581                 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
582                 
583         /* Validate the pointers */
584         if (!n_hdlc)
585                 return -EIO;
586
587         /* verify user access to buffer */
588         if (!access_ok(VERIFY_WRITE, buf, nr)) {
589                 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
590                 "buffer\n", __FILE__, __LINE__);
591                 return -EFAULT;
592         }
593
594         for (;;) {
595                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
596                         return -EIO;
597
598                 n_hdlc = tty2n_hdlc (tty);
599                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
600                          tty != n_hdlc->tty)
601                         return 0;
602
603                 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
604                 if (rbuf)
605                         break;
606                         
607                 /* no data */
608                 if (file->f_flags & O_NONBLOCK)
609                         return -EAGAIN;
610                         
611                 interruptible_sleep_on (&tty->read_wait);
612                 if (signal_pending(current))
613                         return -EINTR;
614         }
615                 
616         if (rbuf->count > nr)
617                 /* frame too large for caller's buffer (discard frame) */
618                 ret = -EOVERFLOW;
619         else {
620                 /* Copy the data to the caller's buffer */
621                 if (copy_to_user(buf, rbuf->buf, rbuf->count))
622                         ret = -EFAULT;
623                 else
624                         ret = rbuf->count;
625         }
626         
627         /* return HDLC buffer to free list unless the free list */
628         /* count has exceeded the default value, in which case the */
629         /* buffer is freed back to the OS to conserve memory */
630         if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
631                 kfree(rbuf);
632         else    
633                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
634         
635         return ret;
636         
637 }       /* end of n_hdlc_tty_read() */
638
639 /**
640  * n_hdlc_tty_write - write a single frame of data to device
641  * @tty - pointer to associated tty device instance data
642  * @file - pointer to file object data
643  * @data - pointer to transmit data (one frame)
644  * @count - size of transmit frame in bytes
645  *              
646  * Returns the number of bytes written (or error code).
647  */
648 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
649                             const unsigned char *data, size_t count)
650 {
651         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
652         int error = 0;
653         DECLARE_WAITQUEUE(wait, current);
654         struct n_hdlc_buf *tbuf;
655
656         if (debuglevel >= DEBUG_LEVEL_INFO)     
657                 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
658                         __FILE__,__LINE__,count);
659                 
660         /* Verify pointers */
661         if (!n_hdlc)
662                 return -EIO;
663
664         if (n_hdlc->magic != HDLC_MAGIC)
665                 return -EIO;
666
667         /* verify frame size */
668         if (count > maxframe ) {
669                 if (debuglevel & DEBUG_LEVEL_INFO)
670                         printk (KERN_WARNING
671                                 "n_hdlc_tty_write: truncating user packet "
672                                 "from %lu to %d\n", (unsigned long) count,
673                                 maxframe );
674                 count = maxframe;
675         }
676         
677         add_wait_queue(&tty->write_wait, &wait);
678         set_current_state(TASK_INTERRUPTIBLE);
679         
680         /* Allocate transmit buffer */
681         /* sleep until transmit buffer available */             
682         while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
683                 schedule();
684                         
685                 n_hdlc = tty2n_hdlc (tty);
686                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC || 
687                     tty != n_hdlc->tty) {
688                         printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
689                         error = -EIO;
690                         break;
691                 }
692                         
693                 if (signal_pending(current)) {
694                         error = -EINTR;
695                         break;
696                 }
697         }
698
699         set_current_state(TASK_RUNNING);
700         remove_wait_queue(&tty->write_wait, &wait);
701
702         if (!error) {           
703                 /* Retrieve the user's buffer */
704                 memcpy(tbuf->buf, data, count);
705
706                 /* Send the data */
707                 tbuf->count = error = count;
708                 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
709                 n_hdlc_send_frames(n_hdlc,tty);
710         }
711
712         return error;
713         
714 }       /* end of n_hdlc_tty_write() */
715
716 /**
717  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
718  * @tty - pointer to tty instance data
719  * @file - pointer to open file object for device
720  * @cmd - IOCTL command code
721  * @arg - argument for IOCTL call (cmd dependent)
722  *
723  * Returns command dependent result.
724  */
725 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
726                             unsigned int cmd, unsigned long arg)
727 {
728         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
729         int error = 0;
730         int count;
731         unsigned long flags;
732         
733         if (debuglevel >= DEBUG_LEVEL_INFO)     
734                 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
735                         __FILE__,__LINE__,cmd);
736                 
737         /* Verify the status of the device */
738         if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
739                 return -EBADF;
740
741         switch (cmd) {
742         case FIONREAD:
743                 /* report count of read data available */
744                 /* in next available frame (if any) */
745                 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
746                 if (n_hdlc->rx_buf_list.head)
747                         count = n_hdlc->rx_buf_list.head->count;
748                 else
749                         count = 0;
750                 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
751                 error = put_user(count, (int __user *)arg);
752                 break;
753
754         case TIOCOUTQ:
755                 /* get the pending tx byte count in the driver */
756                 count = tty->driver->chars_in_buffer ?
757                                 tty->driver->chars_in_buffer(tty) : 0;
758                 /* add size of next output frame in queue */
759                 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
760                 if (n_hdlc->tx_buf_list.head)
761                         count += n_hdlc->tx_buf_list.head->count;
762                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
763                 error = put_user(count, (int __user *)arg);
764                 break;
765
766         default:
767                 error = n_tty_ioctl (tty, file, cmd, arg);
768                 break;
769         }
770         return error;
771         
772 }       /* end of n_hdlc_tty_ioctl() */
773
774 /**
775  * n_hdlc_tty_poll - TTY callback for poll system call
776  * @tty - pointer to tty instance data
777  * @filp - pointer to open file object for device
778  * @poll_table - wait queue for operations
779  * 
780  * Determine which operations (read/write) will not block and return info
781  * to caller.
782  * Returns a bit mask containing info on which ops will not block.
783  */
784 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
785                                     poll_table *wait)
786 {
787         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
788         unsigned int mask = 0;
789
790         if (debuglevel >= DEBUG_LEVEL_INFO)     
791                 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
792                 
793         if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
794                 /* queue current process into any wait queue that */
795                 /* may awaken in the future (read and write) */
796
797                 poll_wait(filp, &tty->read_wait, wait);
798                 poll_wait(filp, &tty->write_wait, wait);
799
800                 /* set bits for operations that won't block */
801                 if(n_hdlc->rx_buf_list.head)
802                         mask |= POLLIN | POLLRDNORM;    /* readable */
803                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
804                         mask |= POLLHUP;
805                 if(tty_hung_up_p(filp))
806                         mask |= POLLHUP;
807                 if(n_hdlc->tx_free_buf_list.head)
808                         mask |= POLLOUT | POLLWRNORM;   /* writable */
809         }
810         return mask;
811 }       /* end of n_hdlc_tty_poll() */
812
813 /**
814  * n_hdlc_alloc - allocate an n_hdlc instance data structure
815  *
816  * Returns a pointer to newly created structure if success, otherwise %NULL
817  */
818 static struct n_hdlc *n_hdlc_alloc(void)
819 {
820         struct n_hdlc_buf *buf;
821         int i;
822         struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
823
824         if (!n_hdlc)
825                 return NULL;
826
827         memset(n_hdlc, 0, sizeof(*n_hdlc));
828
829         n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
830         n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
831         n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
832         n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
833         
834         /* allocate free rx buffer list */
835         for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
836                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
837                 if (buf)
838                         n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
839                 else if (debuglevel >= DEBUG_LEVEL_INFO)        
840                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
841         }
842         
843         /* allocate free tx buffer list */
844         for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
845                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
846                 if (buf)
847                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
848                 else if (debuglevel >= DEBUG_LEVEL_INFO)        
849                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
850         }
851         
852         /* Initialize the control block */
853         n_hdlc->magic  = HDLC_MAGIC;
854         n_hdlc->flags  = 0;
855         
856         return n_hdlc;
857         
858 }       /* end of n_hdlc_alloc() */
859
860 /**
861  * n_hdlc_buf_list_init - initialize specified HDLC buffer list
862  * @list - pointer to buffer list
863  */
864 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
865 {
866         memset(list, 0, sizeof(*list));
867         spin_lock_init(&list->spinlock);
868 }       /* end of n_hdlc_buf_list_init() */
869
870 /**
871  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
872  * @list - pointer to buffer list
873  * @buf - pointer to buffer
874  */
875 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
876                            struct n_hdlc_buf *buf)
877 {
878         unsigned long flags;
879         spin_lock_irqsave(&list->spinlock,flags);
880         
881         buf->link=NULL;
882         if(list->tail)
883                 list->tail->link = buf;
884         else
885                 list->head = buf;
886         list->tail = buf;
887         (list->count)++;
888         
889         spin_unlock_irqrestore(&list->spinlock,flags);
890         
891 }       /* end of n_hdlc_buf_put() */
892
893 /**
894  * n_hdlc_buf_get - remove and return an HDLC buffer from list
895  * @list - pointer to HDLC buffer list
896  * 
897  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
898  * list.
899  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
900  */
901 static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
902 {
903         unsigned long flags;
904         struct n_hdlc_buf *buf;
905         spin_lock_irqsave(&list->spinlock,flags);
906         
907         buf = list->head;
908         if (buf) {
909                 list->head = buf->link;
910                 (list->count)--;
911         }
912         if (!list->head)
913                 list->tail = NULL;
914         
915         spin_unlock_irqrestore(&list->spinlock,flags);
916         return buf;
917         
918 }       /* end of n_hdlc_buf_get() */
919
920 static char hdlc_banner[] __initdata =
921         KERN_INFO "HDLC line discipline: version " HDLC_VERSION
922         ", maxframe=%u\n";
923 static char hdlc_register_ok[] __initdata =
924         KERN_INFO "N_HDLC line discipline registered.\n";
925 static char hdlc_register_fail[] __initdata =
926         KERN_ERR "error registering line discipline: %d\n";
927 static char hdlc_init_fail[] __initdata =
928         KERN_INFO "N_HDLC: init failure %d\n";
929
930 static int __init n_hdlc_init(void)
931 {
932         int status;
933
934         /* range check maxframe arg */
935         if (maxframe < 4096)
936                 maxframe = 4096;
937         else if (maxframe > 65535)
938                 maxframe = 65535;
939
940         printk(hdlc_banner, maxframe);
941
942         status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
943         if (!status)
944                 printk(hdlc_register_ok);
945         else
946                 printk(hdlc_register_fail, status);
947
948         if (status)
949                 printk(hdlc_init_fail, status);
950         return status;
951         
952 }       /* end of init_module() */
953
954 static char hdlc_unregister_ok[] __exitdata =
955         KERN_INFO "N_HDLC: line discipline unregistered\n";
956 static char hdlc_unregister_fail[] __exitdata =
957         KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
958
959 static void __exit n_hdlc_exit(void)
960 {
961         /* Release tty registration of line discipline */
962         int status = tty_unregister_ldisc(N_HDLC);
963
964         if (status)
965                 printk(hdlc_unregister_fail, status);
966         else
967                 printk(hdlc_unregister_ok);
968 }
969
970 module_init(n_hdlc_init);
971 module_exit(n_hdlc_exit);
972
973 MODULE_LICENSE("GPL");
974 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
975 module_param(debuglevel, int, 0);
976 module_param(maxframe, int, 0);
977 MODULE_ALIAS_LDISC(N_HDLC);