Revert "ARM: tegra: tegratab: dummy change"
[linux-2.6.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 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_list_init(struct n_hdlc_buf_list *list);
163 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
164                            struct n_hdlc_buf *buf);
165 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
166
167 /* Local functions */
168
169 static struct n_hdlc *n_hdlc_alloc (void);
170
171 /* debug level can be set by insmod for debugging purposes */
172 #define DEBUG_LEVEL_INFO        1
173 static int debuglevel;
174
175 /* max frame size for memory allocations */
176 static int maxframe = 4096;
177
178 /* TTY callbacks */
179
180 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
181                            __u8 __user *buf, size_t nr);
182 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
183                             const unsigned char *buf, size_t nr);
184 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
185                             unsigned int cmd, unsigned long arg);
186 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
187                                     poll_table *wait);
188 static int n_hdlc_tty_open(struct tty_struct *tty);
189 static void n_hdlc_tty_close(struct tty_struct *tty);
190 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
191                                char *fp, int count);
192 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
193
194 #define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
195
196 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
197 #define n_hdlc2tty(n_hdlc)      ((n_hdlc)->tty)
198
199 static void flush_rx_queue(struct tty_struct *tty)
200 {
201         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
202         struct n_hdlc_buf *buf;
203
204         while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
205                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
206 }
207
208 static void flush_tx_queue(struct tty_struct *tty)
209 {
210         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
211         struct n_hdlc_buf *buf;
212         unsigned long flags;
213
214         while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
215                 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
216         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
217         if (n_hdlc->tbuf) {
218                 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, n_hdlc->tbuf);
219                 n_hdlc->tbuf = NULL;
220         }
221         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
222 }
223
224 static struct tty_ldisc_ops n_hdlc_ldisc = {
225         .owner          = THIS_MODULE,
226         .magic          = TTY_LDISC_MAGIC,
227         .name           = "hdlc",
228         .open           = n_hdlc_tty_open,
229         .close          = n_hdlc_tty_close,
230         .read           = n_hdlc_tty_read,
231         .write          = n_hdlc_tty_write,
232         .ioctl          = n_hdlc_tty_ioctl,
233         .poll           = n_hdlc_tty_poll,
234         .receive_buf    = n_hdlc_tty_receive,
235         .write_wakeup   = n_hdlc_tty_wakeup,
236         .flush_buffer   = flush_rx_queue,
237 };
238
239 /**
240  * n_hdlc_release - release an n_hdlc per device line discipline info structure
241  * @n_hdlc - per device line discipline info structure
242  */
243 static void n_hdlc_release(struct n_hdlc *n_hdlc)
244 {
245         struct tty_struct *tty = n_hdlc2tty (n_hdlc);
246         struct n_hdlc_buf *buf;
247         
248         if (debuglevel >= DEBUG_LEVEL_INFO)     
249                 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
250                 
251         /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
252         wake_up_interruptible (&tty->read_wait);
253         wake_up_interruptible (&tty->write_wait);
254
255         if (tty->disc_data == n_hdlc)
256                 tty->disc_data = NULL;  /* Break the tty->n_hdlc link */
257
258         /* Release transmit and receive buffers */
259         for(;;) {
260                 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
261                 if (buf) {
262                         kfree(buf);
263                 } else
264                         break;
265         }
266         for(;;) {
267                 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
268                 if (buf) {
269                         kfree(buf);
270                 } else
271                         break;
272         }
273         for(;;) {
274                 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
275                 if (buf) {
276                         kfree(buf);
277                 } else
278                         break;
279         }
280         for(;;) {
281                 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
282                 if (buf) {
283                         kfree(buf);
284                 } else
285                         break;
286         }
287         kfree(n_hdlc->tbuf);
288         kfree(n_hdlc);
289         
290 }       /* end of n_hdlc_release() */
291
292 /**
293  * n_hdlc_tty_close - line discipline close
294  * @tty - pointer to tty info structure
295  *
296  * Called when the line discipline is changed to something
297  * else, the tty is closed, or the tty detects a hangup.
298  */
299 static void n_hdlc_tty_close(struct tty_struct *tty)
300 {
301         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
302
303         if (debuglevel >= DEBUG_LEVEL_INFO)     
304                 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
305                 
306         if (n_hdlc != NULL) {
307                 if (n_hdlc->magic != HDLC_MAGIC) {
308                         printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
309                         return;
310                 }
311 #if defined(TTY_NO_WRITE_SPLIT)
312                 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
313 #endif
314                 tty->disc_data = NULL;
315                 if (tty == n_hdlc->backup_tty)
316                         n_hdlc->backup_tty = NULL;
317                 if (tty != n_hdlc->tty)
318                         return;
319                 if (n_hdlc->backup_tty) {
320                         n_hdlc->tty = n_hdlc->backup_tty;
321                 } else {
322                         n_hdlc_release (n_hdlc);
323                 }
324         }
325         
326         if (debuglevel >= DEBUG_LEVEL_INFO)     
327                 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
328                 
329 }       /* end of n_hdlc_tty_close() */
330
331 /**
332  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
333  * @tty - pointer to tty info structure
334  *
335  * Returns 0 if success, otherwise error code
336  */
337 static int n_hdlc_tty_open (struct tty_struct *tty)
338 {
339         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
340
341         if (debuglevel >= DEBUG_LEVEL_INFO)     
342                 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
343                 __FILE__,__LINE__,
344                 tty->name);
345                 
346         /* There should not be an existing table for this slot. */
347         if (n_hdlc) {
348                 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
349                 return -EEXIST;
350         }
351         
352         n_hdlc = n_hdlc_alloc();
353         if (!n_hdlc) {
354                 printk (KERN_ERR "n_hdlc_alloc failed\n");
355                 return -ENFILE;
356         }
357                 
358         tty->disc_data = n_hdlc;
359         n_hdlc->tty    = tty;
360         tty->receive_room = 65536;
361         
362 #if defined(TTY_NO_WRITE_SPLIT)
363         /* change tty_io write() to not split large writes into 8K chunks */
364         set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
365 #endif
366         
367         /* flush receive data from driver */
368         tty_driver_flush_buffer(tty);
369                 
370         if (debuglevel >= DEBUG_LEVEL_INFO)     
371                 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
372                 
373         return 0;
374         
375 }       /* end of n_tty_hdlc_open() */
376
377 /**
378  * n_hdlc_send_frames - send frames on pending send buffer list
379  * @n_hdlc - pointer to ldisc instance data
380  * @tty - pointer to tty instance data
381  *
382  * Send frames on pending send buffer list until the driver does not accept a
383  * frame (busy) this function is called after adding a frame to the send buffer
384  * list and by the tty wakeup callback.
385  */
386 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
387 {
388         register int actual;
389         unsigned long flags;
390         struct n_hdlc_buf *tbuf;
391
392         if (debuglevel >= DEBUG_LEVEL_INFO)     
393                 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
394  check_again:
395                 
396         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
397         if (n_hdlc->tbusy) {
398                 n_hdlc->woke_up = 1;
399                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
400                 return;
401         }
402         n_hdlc->tbusy = 1;
403         n_hdlc->woke_up = 0;
404         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
405
406         /* get current transmit buffer or get new transmit */
407         /* buffer from list of pending transmit buffers */
408                 
409         tbuf = n_hdlc->tbuf;
410         if (!tbuf)
411                 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
412                 
413         while (tbuf) {
414                 if (debuglevel >= DEBUG_LEVEL_INFO)     
415                         printk("%s(%d)sending frame %p, count=%d\n",
416                                 __FILE__,__LINE__,tbuf,tbuf->count);
417                         
418                 /* Send the next block of data to device */
419                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
420                 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
421
422                 /* rollback was possible and has been done */
423                 if (actual == -ERESTARTSYS) {
424                         n_hdlc->tbuf = tbuf;
425                         break;
426                 }
427                 /* if transmit error, throw frame away by */
428                 /* pretending it was accepted by driver */
429                 if (actual < 0)
430                         actual = tbuf->count;
431                 
432                 if (actual == tbuf->count) {
433                         if (debuglevel >= DEBUG_LEVEL_INFO)     
434                                 printk("%s(%d)frame %p completed\n",
435                                         __FILE__,__LINE__,tbuf);
436                                         
437                         /* free current transmit buffer */
438                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
439                         
440                         /* this tx buffer is done */
441                         n_hdlc->tbuf = NULL;
442                         
443                         /* wait up sleeping writers */
444                         wake_up_interruptible(&tty->write_wait);
445         
446                         /* get next pending transmit buffer */
447                         tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
448                 } else {
449                         if (debuglevel >= DEBUG_LEVEL_INFO)     
450                                 printk("%s(%d)frame %p pending\n",
451                                         __FILE__,__LINE__,tbuf);
452                                         
453                         /* buffer not accepted by driver */
454                         /* set this buffer as pending buffer */
455                         n_hdlc->tbuf = tbuf;
456                         break;
457                 }
458         }
459         
460         if (!tbuf)
461                 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
462         
463         /* Clear the re-entry flag */
464         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
465         n_hdlc->tbusy = 0;
466         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 
467         
468         if (n_hdlc->woke_up)
469           goto check_again;
470
471         if (debuglevel >= DEBUG_LEVEL_INFO)     
472                 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
473                 
474 }       /* end of n_hdlc_send_frames() */
475
476 /**
477  * n_hdlc_tty_wakeup - Callback for transmit wakeup
478  * @tty - pointer to associated tty instance data
479  *
480  * Called when low level device driver can accept more send data.
481  */
482 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
483 {
484         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
485
486         if (debuglevel >= DEBUG_LEVEL_INFO)     
487                 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
488                 
489         if (!n_hdlc)
490                 return;
491
492         if (tty != n_hdlc->tty) {
493                 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
494                 return;
495         }
496
497         n_hdlc_send_frames (n_hdlc, tty);
498                 
499 }       /* end of n_hdlc_tty_wakeup() */
500
501 /**
502  * n_hdlc_tty_receive - Called by tty driver when receive data is available
503  * @tty - pointer to tty instance data
504  * @data - pointer to received data
505  * @flags - pointer to flags for data
506  * @count - count of received data in bytes
507  *
508  * Called by tty low level driver when receive data is available. Data is
509  * interpreted as one HDLC frame.
510  */
511 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
512                                char *flags, int count)
513 {
514         register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
515         register struct n_hdlc_buf *buf;
516
517         if (debuglevel >= DEBUG_LEVEL_INFO)     
518                 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
519                         __FILE__,__LINE__, count);
520                 
521         /* This can happen if stuff comes in on the backup tty */
522         if (!n_hdlc || tty != n_hdlc->tty)
523                 return;
524                 
525         /* verify line is using HDLC discipline */
526         if (n_hdlc->magic != HDLC_MAGIC) {
527                 printk("%s(%d) line not using HDLC discipline\n",
528                         __FILE__,__LINE__);
529                 return;
530         }
531         
532         if ( count>maxframe ) {
533                 if (debuglevel >= DEBUG_LEVEL_INFO)     
534                         printk("%s(%d) rx count>maxframesize, data discarded\n",
535                                __FILE__,__LINE__);
536                 return;
537         }
538
539         /* get a free HDLC buffer */    
540         buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
541         if (!buf) {
542                 /* no buffers in free list, attempt to allocate another rx buffer */
543                 /* unless the maximum count has been reached */
544                 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
545                         buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
546         }
547         
548         if (!buf) {
549                 if (debuglevel >= DEBUG_LEVEL_INFO)     
550                         printk("%s(%d) no more rx buffers, data discarded\n",
551                                __FILE__,__LINE__);
552                 return;
553         }
554                 
555         /* copy received data to HDLC buffer */
556         memcpy(buf->buf,data,count);
557         buf->count=count;
558
559         /* add HDLC buffer to list of received frames */
560         n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
561         
562         /* wake up any blocked reads and perform async signalling */
563         wake_up_interruptible (&tty->read_wait);
564         if (n_hdlc->tty->fasync != NULL)
565                 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
566
567 }       /* end of n_hdlc_tty_receive() */
568
569 /**
570  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
571  * @tty - pointer to tty instance data
572  * @file - pointer to open file object
573  * @buf - pointer to returned data buffer
574  * @nr - size of returned data buffer
575  *      
576  * Returns the number of bytes returned or error code.
577  */
578 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
579                            __u8 __user *buf, size_t nr)
580 {
581         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
582         int ret = 0;
583         struct n_hdlc_buf *rbuf;
584         DECLARE_WAITQUEUE(wait, current);
585
586         if (debuglevel >= DEBUG_LEVEL_INFO)     
587                 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
588                 
589         /* Validate the pointers */
590         if (!n_hdlc)
591                 return -EIO;
592
593         /* verify user access to buffer */
594         if (!access_ok(VERIFY_WRITE, buf, nr)) {
595                 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
596                 "buffer\n", __FILE__, __LINE__);
597                 return -EFAULT;
598         }
599
600         add_wait_queue(&tty->read_wait, &wait);
601
602         for (;;) {
603                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
604                         ret = -EIO;
605                         break;
606                 }
607                 if (tty_hung_up_p(file))
608                         break;
609
610                 set_current_state(TASK_INTERRUPTIBLE);
611
612                 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
613                 if (rbuf) {
614                         if (rbuf->count > nr) {
615                                 /* too large for caller's buffer */
616                                 ret = -EOVERFLOW;
617                         } else {
618                                 if (copy_to_user(buf, rbuf->buf, rbuf->count))
619                                         ret = -EFAULT;
620                                 else
621                                         ret = rbuf->count;
622                         }
623
624                         if (n_hdlc->rx_free_buf_list.count >
625                             DEFAULT_RX_BUF_COUNT)
626                                 kfree(rbuf);
627                         else
628                                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
629                         break;
630                 }
631                         
632                 /* no data */
633                 if (file->f_flags & O_NONBLOCK) {
634                         ret = -EAGAIN;
635                         break;
636                 }
637
638                 schedule();
639
640                 if (signal_pending(current)) {
641                         ret = -EINTR;
642                         break;
643                 }
644         }
645
646         remove_wait_queue(&tty->read_wait, &wait);
647         __set_current_state(TASK_RUNNING);
648
649         return ret;
650         
651 }       /* end of n_hdlc_tty_read() */
652
653 /**
654  * n_hdlc_tty_write - write a single frame of data to device
655  * @tty - pointer to associated tty device instance data
656  * @file - pointer to file object data
657  * @data - pointer to transmit data (one frame)
658  * @count - size of transmit frame in bytes
659  *              
660  * Returns the number of bytes written (or error code).
661  */
662 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
663                             const unsigned char *data, size_t count)
664 {
665         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
666         int error = 0;
667         DECLARE_WAITQUEUE(wait, current);
668         struct n_hdlc_buf *tbuf;
669
670         if (debuglevel >= DEBUG_LEVEL_INFO)     
671                 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
672                         __FILE__,__LINE__,count);
673                 
674         /* Verify pointers */
675         if (!n_hdlc)
676                 return -EIO;
677
678         if (n_hdlc->magic != HDLC_MAGIC)
679                 return -EIO;
680
681         /* verify frame size */
682         if (count > maxframe ) {
683                 if (debuglevel & DEBUG_LEVEL_INFO)
684                         printk (KERN_WARNING
685                                 "n_hdlc_tty_write: truncating user packet "
686                                 "from %lu to %d\n", (unsigned long) count,
687                                 maxframe );
688                 count = maxframe;
689         }
690         
691         add_wait_queue(&tty->write_wait, &wait);
692
693         for (;;) {
694                 set_current_state(TASK_INTERRUPTIBLE);
695         
696                 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
697                 if (tbuf)
698                         break;
699
700                 if (file->f_flags & O_NONBLOCK) {
701                         error = -EAGAIN;
702                         break;
703                 }
704                 schedule();
705                         
706                 n_hdlc = tty2n_hdlc (tty);
707                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC || 
708                     tty != n_hdlc->tty) {
709                         printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
710                         error = -EIO;
711                         break;
712                 }
713                         
714                 if (signal_pending(current)) {
715                         error = -EINTR;
716                         break;
717                 }
718         }
719
720         __set_current_state(TASK_RUNNING);
721         remove_wait_queue(&tty->write_wait, &wait);
722
723         if (!error) {           
724                 /* Retrieve the user's buffer */
725                 memcpy(tbuf->buf, data, count);
726
727                 /* Send the data */
728                 tbuf->count = error = count;
729                 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
730                 n_hdlc_send_frames(n_hdlc,tty);
731         }
732
733         return error;
734         
735 }       /* end of n_hdlc_tty_write() */
736
737 /**
738  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
739  * @tty - pointer to tty instance data
740  * @file - pointer to open file object for device
741  * @cmd - IOCTL command code
742  * @arg - argument for IOCTL call (cmd dependent)
743  *
744  * Returns command dependent result.
745  */
746 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
747                             unsigned int cmd, unsigned long arg)
748 {
749         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
750         int error = 0;
751         int count;
752         unsigned long flags;
753         
754         if (debuglevel >= DEBUG_LEVEL_INFO)     
755                 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
756                         __FILE__,__LINE__,cmd);
757                 
758         /* Verify the status of the device */
759         if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
760                 return -EBADF;
761
762         switch (cmd) {
763         case FIONREAD:
764                 /* report count of read data available */
765                 /* in next available frame (if any) */
766                 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
767                 if (n_hdlc->rx_buf_list.head)
768                         count = n_hdlc->rx_buf_list.head->count;
769                 else
770                         count = 0;
771                 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
772                 error = put_user(count, (int __user *)arg);
773                 break;
774
775         case TIOCOUTQ:
776                 /* get the pending tx byte count in the driver */
777                 count = tty_chars_in_buffer(tty);
778                 /* add size of next output frame in queue */
779                 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
780                 if (n_hdlc->tx_buf_list.head)
781                         count += n_hdlc->tx_buf_list.head->count;
782                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
783                 error = put_user(count, (int __user *)arg);
784                 break;
785
786         case TCFLSH:
787                 switch (arg) {
788                 case TCIOFLUSH:
789                 case TCOFLUSH:
790                         flush_tx_queue(tty);
791                 }
792                 /* fall through to default */
793
794         default:
795                 error = n_tty_ioctl_helper(tty, file, cmd, arg);
796                 break;
797         }
798         return error;
799         
800 }       /* end of n_hdlc_tty_ioctl() */
801
802 /**
803  * n_hdlc_tty_poll - TTY callback for poll system call
804  * @tty - pointer to tty instance data
805  * @filp - pointer to open file object for device
806  * @poll_table - wait queue for operations
807  * 
808  * Determine which operations (read/write) will not block and return info
809  * to caller.
810  * Returns a bit mask containing info on which ops will not block.
811  */
812 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
813                                     poll_table *wait)
814 {
815         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
816         unsigned int mask = 0;
817
818         if (debuglevel >= DEBUG_LEVEL_INFO)     
819                 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
820                 
821         if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
822                 /* queue current process into any wait queue that */
823                 /* may awaken in the future (read and write) */
824
825                 poll_wait(filp, &tty->read_wait, wait);
826                 poll_wait(filp, &tty->write_wait, wait);
827
828                 /* set bits for operations that won't block */
829                 if (n_hdlc->rx_buf_list.head)
830                         mask |= POLLIN | POLLRDNORM;    /* readable */
831                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
832                         mask |= POLLHUP;
833                 if (tty_hung_up_p(filp))
834                         mask |= POLLHUP;
835                 if (!tty_is_writelocked(tty) &&
836                                 n_hdlc->tx_free_buf_list.head)
837                         mask |= POLLOUT | POLLWRNORM;   /* writable */
838         }
839         return mask;
840 }       /* end of n_hdlc_tty_poll() */
841
842 /**
843  * n_hdlc_alloc - allocate an n_hdlc instance data structure
844  *
845  * Returns a pointer to newly created structure if success, otherwise %NULL
846  */
847 static struct n_hdlc *n_hdlc_alloc(void)
848 {
849         struct n_hdlc_buf *buf;
850         int i;
851         struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
852
853         if (!n_hdlc)
854                 return NULL;
855
856         memset(n_hdlc, 0, sizeof(*n_hdlc));
857
858         n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
859         n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
860         n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
861         n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
862         
863         /* allocate free rx buffer list */
864         for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
865                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
866                 if (buf)
867                         n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
868                 else if (debuglevel >= DEBUG_LEVEL_INFO)        
869                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
870         }
871         
872         /* allocate free tx buffer list */
873         for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
874                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
875                 if (buf)
876                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
877                 else if (debuglevel >= DEBUG_LEVEL_INFO)        
878                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
879         }
880         
881         /* Initialize the control block */
882         n_hdlc->magic  = HDLC_MAGIC;
883         n_hdlc->flags  = 0;
884         
885         return n_hdlc;
886         
887 }       /* end of n_hdlc_alloc() */
888
889 /**
890  * n_hdlc_buf_list_init - initialize specified HDLC buffer list
891  * @list - pointer to buffer list
892  */
893 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
894 {
895         memset(list, 0, sizeof(*list));
896         spin_lock_init(&list->spinlock);
897 }       /* end of n_hdlc_buf_list_init() */
898
899 /**
900  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
901  * @list - pointer to buffer list
902  * @buf - pointer to buffer
903  */
904 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
905                            struct n_hdlc_buf *buf)
906 {
907         unsigned long flags;
908         spin_lock_irqsave(&list->spinlock,flags);
909         
910         buf->link=NULL;
911         if (list->tail)
912                 list->tail->link = buf;
913         else
914                 list->head = buf;
915         list->tail = buf;
916         (list->count)++;
917         
918         spin_unlock_irqrestore(&list->spinlock,flags);
919         
920 }       /* end of n_hdlc_buf_put() */
921
922 /**
923  * n_hdlc_buf_get - remove and return an HDLC buffer from list
924  * @list - pointer to HDLC buffer list
925  * 
926  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
927  * list.
928  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
929  */
930 static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
931 {
932         unsigned long flags;
933         struct n_hdlc_buf *buf;
934         spin_lock_irqsave(&list->spinlock,flags);
935         
936         buf = list->head;
937         if (buf) {
938                 list->head = buf->link;
939                 (list->count)--;
940         }
941         if (!list->head)
942                 list->tail = NULL;
943         
944         spin_unlock_irqrestore(&list->spinlock,flags);
945         return buf;
946         
947 }       /* end of n_hdlc_buf_get() */
948
949 static char hdlc_banner[] __initdata =
950         KERN_INFO "HDLC line discipline maxframe=%u\n";
951 static char hdlc_register_ok[] __initdata =
952         KERN_INFO "N_HDLC line discipline registered.\n";
953 static char hdlc_register_fail[] __initdata =
954         KERN_ERR "error registering line discipline: %d\n";
955 static char hdlc_init_fail[] __initdata =
956         KERN_INFO "N_HDLC: init failure %d\n";
957
958 static int __init n_hdlc_init(void)
959 {
960         int status;
961
962         /* range check maxframe arg */
963         if (maxframe < 4096)
964                 maxframe = 4096;
965         else if (maxframe > 65535)
966                 maxframe = 65535;
967
968         printk(hdlc_banner, maxframe);
969
970         status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
971         if (!status)
972                 printk(hdlc_register_ok);
973         else
974                 printk(hdlc_register_fail, status);
975
976         if (status)
977                 printk(hdlc_init_fail, status);
978         return status;
979         
980 }       /* end of init_module() */
981
982 static char hdlc_unregister_ok[] __exitdata =
983         KERN_INFO "N_HDLC: line discipline unregistered\n";
984 static char hdlc_unregister_fail[] __exitdata =
985         KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
986
987 static void __exit n_hdlc_exit(void)
988 {
989         /* Release tty registration of line discipline */
990         int status = tty_unregister_ldisc(N_HDLC);
991
992         if (status)
993                 printk(hdlc_unregister_fail, status);
994         else
995                 printk(hdlc_unregister_ok);
996 }
997
998 module_init(n_hdlc_init);
999 module_exit(n_hdlc_exit);
1000
1001 MODULE_LICENSE("GPL");
1002 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
1003 module_param(debuglevel, int, 0);
1004 module_param(maxframe, int, 0);
1005 MODULE_ALIAS_LDISC(N_HDLC);