[PATCH] drivers/char/pc8736x_gpio.c: unexport a static struct
[linux-2.6.git] / 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/module.h>
85 #include <linux/init.h>
86 #include <linux/kernel.h>
87 #include <linux/sched.h>
88 #include <linux/types.h>
89 #include <linux/fcntl.h>
90 #include <linux/interrupt.h>
91 #include <linux/ptrace.h>
92
93 #undef VERSION
94 #define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
95
96 #include <linux/poll.h>
97 #include <linux/in.h>
98 #include <linux/ioctl.h>
99 #include <linux/slab.h>
100 #include <linux/tty.h>
101 #include <linux/errno.h>
102 #include <linux/string.h>       /* used in new tty drivers */
103 #include <linux/signal.h>       /* used in new tty drivers */
104 #include <linux/if.h>
105 #include <linux/bitops.h>
106
107 #include <asm/system.h>
108 #include <asm/termios.h>
109 #include <asm/uaccess.h>
110
111 /*
112  * Buffers for individual HDLC frames
113  */
114 #define MAX_HDLC_FRAME_SIZE 65535 
115 #define DEFAULT_RX_BUF_COUNT 10
116 #define MAX_RX_BUF_COUNT 60
117 #define DEFAULT_TX_BUF_COUNT 1
118
119 struct n_hdlc_buf {
120         struct n_hdlc_buf *link;
121         int               count;
122         char              buf[1];
123 };
124
125 #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
126
127 struct n_hdlc_buf_list {
128         struct n_hdlc_buf *head;
129         struct n_hdlc_buf *tail;
130         int               count;
131         spinlock_t        spinlock;
132 };
133
134 /**
135  * struct n_hdlc - per device instance data structure
136  * @magic - magic value for structure
137  * @flags - miscellaneous control flags
138  * @tty - ptr to TTY structure
139  * @backup_tty - TTY to use if tty gets closed
140  * @tbusy - reentrancy flag for tx wakeup code
141  * @woke_up - FIXME: describe this field
142  * @tbuf - currently transmitting tx buffer
143  * @tx_buf_list - list of pending transmit frame buffers
144  * @rx_buf_list - list of received frame buffers
145  * @tx_free_buf_list - list unused transmit frame buffers
146  * @rx_free_buf_list - list unused received frame buffers
147  */
148 struct n_hdlc {
149         int                     magic;
150         __u32                   flags;
151         struct tty_struct       *tty;
152         struct tty_struct       *backup_tty;
153         int                     tbusy;
154         int                     woke_up;
155         struct n_hdlc_buf       *tbuf;
156         struct n_hdlc_buf_list  tx_buf_list;
157         struct n_hdlc_buf_list  rx_buf_list;
158         struct n_hdlc_buf_list  tx_free_buf_list;
159         struct n_hdlc_buf_list  rx_free_buf_list;
160 };
161
162 /*
163  * HDLC buffer list manipulation functions
164  */
165 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list);
166 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
167                            struct n_hdlc_buf *buf);
168 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
169
170 /* Local functions */
171
172 static struct n_hdlc *n_hdlc_alloc (void);
173
174 /* debug level can be set by insmod for debugging purposes */
175 #define DEBUG_LEVEL_INFO        1
176 static int debuglevel;
177
178 /* max frame size for memory allocations */
179 static int maxframe = 4096;
180
181 /* TTY callbacks */
182
183 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
184                            __u8 __user *buf, size_t nr);
185 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
186                             const unsigned char *buf, size_t nr);
187 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
188                             unsigned int cmd, unsigned long arg);
189 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
190                                     poll_table *wait);
191 static int n_hdlc_tty_open(struct tty_struct *tty);
192 static void n_hdlc_tty_close(struct tty_struct *tty);
193 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
194                                char *fp, int count);
195 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
196
197 #define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
198
199 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
200 #define n_hdlc2tty(n_hdlc)      ((n_hdlc)->tty)
201
202 static struct tty_ldisc n_hdlc_ldisc = {
203         .owner          = THIS_MODULE,
204         .magic          = TTY_LDISC_MAGIC,
205         .name           = "hdlc",
206         .open           = n_hdlc_tty_open,
207         .close          = n_hdlc_tty_close,
208         .read           = n_hdlc_tty_read,
209         .write          = n_hdlc_tty_write,
210         .ioctl          = n_hdlc_tty_ioctl,
211         .poll           = n_hdlc_tty_poll,
212         .receive_buf    = n_hdlc_tty_receive,
213         .write_wakeup   = n_hdlc_tty_wakeup,
214 };
215
216 /**
217  * n_hdlc_release - release an n_hdlc per device line discipline info structure
218  * @n_hdlc - per device line discipline info structure
219  */
220 static void n_hdlc_release(struct n_hdlc *n_hdlc)
221 {
222         struct tty_struct *tty = n_hdlc2tty (n_hdlc);
223         struct n_hdlc_buf *buf;
224         
225         if (debuglevel >= DEBUG_LEVEL_INFO)     
226                 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
227                 
228         /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
229         wake_up_interruptible (&tty->read_wait);
230         wake_up_interruptible (&tty->write_wait);
231
232         if (tty != NULL && tty->disc_data == n_hdlc)
233                 tty->disc_data = NULL;  /* Break the tty->n_hdlc link */
234
235         /* Release transmit and receive buffers */
236         for(;;) {
237                 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
238                 if (buf) {
239                         kfree(buf);
240                 } else
241                         break;
242         }
243         for(;;) {
244                 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
245                 if (buf) {
246                         kfree(buf);
247                 } else
248                         break;
249         }
250         for(;;) {
251                 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
252                 if (buf) {
253                         kfree(buf);
254                 } else
255                         break;
256         }
257         for(;;) {
258                 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
259                 if (buf) {
260                         kfree(buf);
261                 } else
262                         break;
263         }
264         kfree(n_hdlc->tbuf);
265         kfree(n_hdlc);
266         
267 }       /* end of n_hdlc_release() */
268
269 /**
270  * n_hdlc_tty_close - line discipline close
271  * @tty - pointer to tty info structure
272  *
273  * Called when the line discipline is changed to something
274  * else, the tty is closed, or the tty detects a hangup.
275  */
276 static void n_hdlc_tty_close(struct tty_struct *tty)
277 {
278         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
279
280         if (debuglevel >= DEBUG_LEVEL_INFO)     
281                 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
282                 
283         if (n_hdlc != NULL) {
284                 if (n_hdlc->magic != HDLC_MAGIC) {
285                         printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
286                         return;
287                 }
288 #if defined(TTY_NO_WRITE_SPLIT)
289                 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
290 #endif
291                 tty->disc_data = NULL;
292                 if (tty == n_hdlc->backup_tty)
293                         n_hdlc->backup_tty = NULL;
294                 if (tty != n_hdlc->tty)
295                         return;
296                 if (n_hdlc->backup_tty) {
297                         n_hdlc->tty = n_hdlc->backup_tty;
298                 } else {
299                         n_hdlc_release (n_hdlc);
300                 }
301         }
302         
303         if (debuglevel >= DEBUG_LEVEL_INFO)     
304                 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
305                 
306 }       /* end of n_hdlc_tty_close() */
307
308 /**
309  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
310  * @tty - pointer to tty info structure
311  *
312  * Returns 0 if success, otherwise error code
313  */
314 static int n_hdlc_tty_open (struct tty_struct *tty)
315 {
316         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
317
318         if (debuglevel >= DEBUG_LEVEL_INFO)     
319                 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
320                 __FILE__,__LINE__,
321                 tty->name);
322                 
323         /* There should not be an existing table for this slot. */
324         if (n_hdlc) {
325                 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
326                 return -EEXIST;
327         }
328         
329         n_hdlc = n_hdlc_alloc();
330         if (!n_hdlc) {
331                 printk (KERN_ERR "n_hdlc_alloc failed\n");
332                 return -ENFILE;
333         }
334                 
335         tty->disc_data = n_hdlc;
336         n_hdlc->tty    = tty;
337         tty->receive_room = 65536;
338         
339 #if defined(TTY_NO_WRITE_SPLIT)
340         /* change tty_io write() to not split large writes into 8K chunks */
341         set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
342 #endif
343         
344         /* Flush any pending characters in the driver and discipline. */
345         
346         if (tty->ldisc.flush_buffer)
347                 tty->ldisc.flush_buffer (tty);
348
349         if (tty->driver->flush_buffer)
350                 tty->driver->flush_buffer (tty);
351                 
352         if (debuglevel >= DEBUG_LEVEL_INFO)     
353                 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
354                 
355         return 0;
356         
357 }       /* end of n_tty_hdlc_open() */
358
359 /**
360  * n_hdlc_send_frames - send frames on pending send buffer list
361  * @n_hdlc - pointer to ldisc instance data
362  * @tty - pointer to tty instance data
363  *
364  * Send frames on pending send buffer list until the driver does not accept a
365  * frame (busy) this function is called after adding a frame to the send buffer
366  * list and by the tty wakeup callback.
367  */
368 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
369 {
370         register int actual;
371         unsigned long flags;
372         struct n_hdlc_buf *tbuf;
373
374         if (debuglevel >= DEBUG_LEVEL_INFO)     
375                 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
376  check_again:
377                 
378         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
379         if (n_hdlc->tbusy) {
380                 n_hdlc->woke_up = 1;
381                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
382                 return;
383         }
384         n_hdlc->tbusy = 1;
385         n_hdlc->woke_up = 0;
386         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
387
388         /* get current transmit buffer or get new transmit */
389         /* buffer from list of pending transmit buffers */
390                 
391         tbuf = n_hdlc->tbuf;
392         if (!tbuf)
393                 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
394                 
395         while (tbuf) {
396                 if (debuglevel >= DEBUG_LEVEL_INFO)     
397                         printk("%s(%d)sending frame %p, count=%d\n",
398                                 __FILE__,__LINE__,tbuf,tbuf->count);
399                         
400                 /* Send the next block of data to device */
401                 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
402                 actual = tty->driver->write(tty, tbuf->buf, tbuf->count);
403                     
404                 /* if transmit error, throw frame away by */
405                 /* pretending it was accepted by driver */
406                 if (actual < 0)
407                         actual = tbuf->count;
408                 
409                 if (actual == tbuf->count) {
410                         if (debuglevel >= DEBUG_LEVEL_INFO)     
411                                 printk("%s(%d)frame %p completed\n",
412                                         __FILE__,__LINE__,tbuf);
413                                         
414                         /* free current transmit buffer */
415                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
416                         
417                         /* this tx buffer is done */
418                         n_hdlc->tbuf = NULL;
419                         
420                         /* wait up sleeping writers */
421                         wake_up_interruptible(&tty->write_wait);
422         
423                         /* get next pending transmit buffer */
424                         tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
425                 } else {
426                         if (debuglevel >= DEBUG_LEVEL_INFO)     
427                                 printk("%s(%d)frame %p pending\n",
428                                         __FILE__,__LINE__,tbuf);
429                                         
430                         /* buffer not accepted by driver */
431                         /* set this buffer as pending buffer */
432                         n_hdlc->tbuf = tbuf;
433                         break;
434                 }
435         }
436         
437         if (!tbuf)
438                 tty->flags  &= ~(1 << TTY_DO_WRITE_WAKEUP);
439         
440         /* Clear the re-entry flag */
441         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
442         n_hdlc->tbusy = 0;
443         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags); 
444         
445         if (n_hdlc->woke_up)
446           goto check_again;
447
448         if (debuglevel >= DEBUG_LEVEL_INFO)     
449                 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
450                 
451 }       /* end of n_hdlc_send_frames() */
452
453 /**
454  * n_hdlc_tty_wakeup - Callback for transmit wakeup
455  * @tty - pointer to associated tty instance data
456  *
457  * Called when low level device driver can accept more send data.
458  */
459 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
460 {
461         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
462
463         if (debuglevel >= DEBUG_LEVEL_INFO)     
464                 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
465                 
466         if (!n_hdlc)
467                 return;
468
469         if (tty != n_hdlc->tty) {
470                 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
471                 return;
472         }
473
474         n_hdlc_send_frames (n_hdlc, tty);
475                 
476 }       /* end of n_hdlc_tty_wakeup() */
477
478 /**
479  * n_hdlc_tty_receive - Called by tty driver when receive data is available
480  * @tty - pointer to tty instance data
481  * @data - pointer to received data
482  * @flags - pointer to flags for data
483  * @count - count of received data in bytes
484  *
485  * Called by tty low level driver when receive data is available. Data is
486  * interpreted as one HDLC frame.
487  */
488 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
489                                char *flags, int count)
490 {
491         register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
492         register struct n_hdlc_buf *buf;
493
494         if (debuglevel >= DEBUG_LEVEL_INFO)     
495                 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
496                         __FILE__,__LINE__, count);
497                 
498         /* This can happen if stuff comes in on the backup tty */
499         if (n_hdlc == 0 || tty != n_hdlc->tty)
500                 return;
501                 
502         /* verify line is using HDLC discipline */
503         if (n_hdlc->magic != HDLC_MAGIC) {
504                 printk("%s(%d) line not using HDLC discipline\n",
505                         __FILE__,__LINE__);
506                 return;
507         }
508         
509         if ( count>maxframe ) {
510                 if (debuglevel >= DEBUG_LEVEL_INFO)     
511                         printk("%s(%d) rx count>maxframesize, data discarded\n",
512                                __FILE__,__LINE__);
513                 return;
514         }
515
516         /* get a free HDLC buffer */    
517         buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
518         if (!buf) {
519                 /* no buffers in free list, attempt to allocate another rx buffer */
520                 /* unless the maximum count has been reached */
521                 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
522                         buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
523         }
524         
525         if (!buf) {
526                 if (debuglevel >= DEBUG_LEVEL_INFO)     
527                         printk("%s(%d) no more rx buffers, data discarded\n",
528                                __FILE__,__LINE__);
529                 return;
530         }
531                 
532         /* copy received data to HDLC buffer */
533         memcpy(buf->buf,data,count);
534         buf->count=count;
535
536         /* add HDLC buffer to list of received frames */
537         n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
538         
539         /* wake up any blocked reads and perform async signalling */
540         wake_up_interruptible (&tty->read_wait);
541         if (n_hdlc->tty->fasync != NULL)
542                 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
543
544 }       /* end of n_hdlc_tty_receive() */
545
546 /**
547  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
548  * @tty - pointer to tty instance data
549  * @file - pointer to open file object
550  * @buf - pointer to returned data buffer
551  * @nr - size of returned data buffer
552  *      
553  * Returns the number of bytes returned or error code.
554  */
555 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
556                            __u8 __user *buf, size_t nr)
557 {
558         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
559         int ret;
560         struct n_hdlc_buf *rbuf;
561
562         if (debuglevel >= DEBUG_LEVEL_INFO)     
563                 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
564                 
565         /* Validate the pointers */
566         if (!n_hdlc)
567                 return -EIO;
568
569         /* verify user access to buffer */
570         if (!access_ok(VERIFY_WRITE, buf, nr)) {
571                 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
572                 "buffer\n", __FILE__, __LINE__);
573                 return -EFAULT;
574         }
575
576         for (;;) {
577                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
578                         return -EIO;
579
580                 n_hdlc = tty2n_hdlc (tty);
581                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
582                          tty != n_hdlc->tty)
583                         return 0;
584
585                 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
586                 if (rbuf)
587                         break;
588                         
589                 /* no data */
590                 if (file->f_flags & O_NONBLOCK)
591                         return -EAGAIN;
592                         
593                 interruptible_sleep_on (&tty->read_wait);
594                 if (signal_pending(current))
595                         return -EINTR;
596         }
597                 
598         if (rbuf->count > nr)
599                 /* frame too large for caller's buffer (discard frame) */
600                 ret = -EOVERFLOW;
601         else {
602                 /* Copy the data to the caller's buffer */
603                 if (copy_to_user(buf, rbuf->buf, rbuf->count))
604                         ret = -EFAULT;
605                 else
606                         ret = rbuf->count;
607         }
608         
609         /* return HDLC buffer to free list unless the free list */
610         /* count has exceeded the default value, in which case the */
611         /* buffer is freed back to the OS to conserve memory */
612         if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
613                 kfree(rbuf);
614         else    
615                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
616         
617         return ret;
618         
619 }       /* end of n_hdlc_tty_read() */
620
621 /**
622  * n_hdlc_tty_write - write a single frame of data to device
623  * @tty - pointer to associated tty device instance data
624  * @file - pointer to file object data
625  * @data - pointer to transmit data (one frame)
626  * @count - size of transmit frame in bytes
627  *              
628  * Returns the number of bytes written (or error code).
629  */
630 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
631                             const unsigned char *data, size_t count)
632 {
633         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
634         int error = 0;
635         DECLARE_WAITQUEUE(wait, current);
636         struct n_hdlc_buf *tbuf;
637
638         if (debuglevel >= DEBUG_LEVEL_INFO)     
639                 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
640                         __FILE__,__LINE__,count);
641                 
642         /* Verify pointers */
643         if (!n_hdlc)
644                 return -EIO;
645
646         if (n_hdlc->magic != HDLC_MAGIC)
647                 return -EIO;
648
649         /* verify frame size */
650         if (count > maxframe ) {
651                 if (debuglevel & DEBUG_LEVEL_INFO)
652                         printk (KERN_WARNING
653                                 "n_hdlc_tty_write: truncating user packet "
654                                 "from %lu to %d\n", (unsigned long) count,
655                                 maxframe );
656                 count = maxframe;
657         }
658         
659         add_wait_queue(&tty->write_wait, &wait);
660         set_current_state(TASK_INTERRUPTIBLE);
661         
662         /* Allocate transmit buffer */
663         /* sleep until transmit buffer available */             
664         while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
665                 schedule();
666                         
667                 n_hdlc = tty2n_hdlc (tty);
668                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC || 
669                     tty != n_hdlc->tty) {
670                         printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
671                         error = -EIO;
672                         break;
673                 }
674                         
675                 if (signal_pending(current)) {
676                         error = -EINTR;
677                         break;
678                 }
679         }
680
681         set_current_state(TASK_RUNNING);
682         remove_wait_queue(&tty->write_wait, &wait);
683
684         if (!error) {           
685                 /* Retrieve the user's buffer */
686                 memcpy(tbuf->buf, data, count);
687
688                 /* Send the data */
689                 tbuf->count = error = count;
690                 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
691                 n_hdlc_send_frames(n_hdlc,tty);
692         }
693
694         return error;
695         
696 }       /* end of n_hdlc_tty_write() */
697
698 /**
699  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
700  * @tty - pointer to tty instance data
701  * @file - pointer to open file object for device
702  * @cmd - IOCTL command code
703  * @arg - argument for IOCTL call (cmd dependent)
704  *
705  * Returns command dependent result.
706  */
707 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
708                             unsigned int cmd, unsigned long arg)
709 {
710         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
711         int error = 0;
712         int count;
713         unsigned long flags;
714         
715         if (debuglevel >= DEBUG_LEVEL_INFO)     
716                 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
717                         __FILE__,__LINE__,cmd);
718                 
719         /* Verify the status of the device */
720         if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
721                 return -EBADF;
722
723         switch (cmd) {
724         case FIONREAD:
725                 /* report count of read data available */
726                 /* in next available frame (if any) */
727                 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
728                 if (n_hdlc->rx_buf_list.head)
729                         count = n_hdlc->rx_buf_list.head->count;
730                 else
731                         count = 0;
732                 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
733                 error = put_user(count, (int __user *)arg);
734                 break;
735
736         case TIOCOUTQ:
737                 /* get the pending tx byte count in the driver */
738                 count = tty->driver->chars_in_buffer ?
739                                 tty->driver->chars_in_buffer(tty) : 0;
740                 /* add size of next output frame in queue */
741                 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
742                 if (n_hdlc->tx_buf_list.head)
743                         count += n_hdlc->tx_buf_list.head->count;
744                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
745                 error = put_user(count, (int __user *)arg);
746                 break;
747
748         default:
749                 error = n_tty_ioctl (tty, file, cmd, arg);
750                 break;
751         }
752         return error;
753         
754 }       /* end of n_hdlc_tty_ioctl() */
755
756 /**
757  * n_hdlc_tty_poll - TTY callback for poll system call
758  * @tty - pointer to tty instance data
759  * @filp - pointer to open file object for device
760  * @poll_table - wait queue for operations
761  * 
762  * Determine which operations (read/write) will not block and return info
763  * to caller.
764  * Returns a bit mask containing info on which ops will not block.
765  */
766 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
767                                     poll_table *wait)
768 {
769         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
770         unsigned int mask = 0;
771
772         if (debuglevel >= DEBUG_LEVEL_INFO)     
773                 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
774                 
775         if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
776                 /* queue current process into any wait queue that */
777                 /* may awaken in the future (read and write) */
778
779                 poll_wait(filp, &tty->read_wait, wait);
780                 poll_wait(filp, &tty->write_wait, wait);
781
782                 /* set bits for operations that won't block */
783                 if(n_hdlc->rx_buf_list.head)
784                         mask |= POLLIN | POLLRDNORM;    /* readable */
785                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
786                         mask |= POLLHUP;
787                 if(tty_hung_up_p(filp))
788                         mask |= POLLHUP;
789                 if(n_hdlc->tx_free_buf_list.head)
790                         mask |= POLLOUT | POLLWRNORM;   /* writable */
791         }
792         return mask;
793 }       /* end of n_hdlc_tty_poll() */
794
795 /**
796  * n_hdlc_alloc - allocate an n_hdlc instance data structure
797  *
798  * Returns a pointer to newly created structure if success, otherwise %NULL
799  */
800 static struct n_hdlc *n_hdlc_alloc(void)
801 {
802         struct n_hdlc_buf *buf;
803         int i;
804         struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
805
806         if (!n_hdlc)
807                 return NULL;
808
809         memset(n_hdlc, 0, sizeof(*n_hdlc));
810
811         n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
812         n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
813         n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
814         n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
815         
816         /* allocate free rx buffer list */
817         for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
818                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
819                 if (buf)
820                         n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
821                 else if (debuglevel >= DEBUG_LEVEL_INFO)        
822                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
823         }
824         
825         /* allocate free tx buffer list */
826         for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
827                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
828                 if (buf)
829                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
830                 else if (debuglevel >= DEBUG_LEVEL_INFO)        
831                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
832         }
833         
834         /* Initialize the control block */
835         n_hdlc->magic  = HDLC_MAGIC;
836         n_hdlc->flags  = 0;
837         
838         return n_hdlc;
839         
840 }       /* end of n_hdlc_alloc() */
841
842 /**
843  * n_hdlc_buf_list_init - initialize specified HDLC buffer list
844  * @list - pointer to buffer list
845  */
846 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
847 {
848         memset(list, 0, sizeof(*list));
849         spin_lock_init(&list->spinlock);
850 }       /* end of n_hdlc_buf_list_init() */
851
852 /**
853  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
854  * @list - pointer to buffer list
855  * @buf - pointer to buffer
856  */
857 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
858                            struct n_hdlc_buf *buf)
859 {
860         unsigned long flags;
861         spin_lock_irqsave(&list->spinlock,flags);
862         
863         buf->link=NULL;
864         if(list->tail)
865                 list->tail->link = buf;
866         else
867                 list->head = buf;
868         list->tail = buf;
869         (list->count)++;
870         
871         spin_unlock_irqrestore(&list->spinlock,flags);
872         
873 }       /* end of n_hdlc_buf_put() */
874
875 /**
876  * n_hdlc_buf_get - remove and return an HDLC buffer from list
877  * @list - pointer to HDLC buffer list
878  * 
879  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
880  * list.
881  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
882  */
883 static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
884 {
885         unsigned long flags;
886         struct n_hdlc_buf *buf;
887         spin_lock_irqsave(&list->spinlock,flags);
888         
889         buf = list->head;
890         if (buf) {
891                 list->head = buf->link;
892                 (list->count)--;
893         }
894         if (!list->head)
895                 list->tail = NULL;
896         
897         spin_unlock_irqrestore(&list->spinlock,flags);
898         return buf;
899         
900 }       /* end of n_hdlc_buf_get() */
901
902 static char hdlc_banner[] __initdata =
903         KERN_INFO "HDLC line discipline: version " HDLC_VERSION
904         ", maxframe=%u\n";
905 static char hdlc_register_ok[] __initdata =
906         KERN_INFO "N_HDLC line discipline registered.\n";
907 static char hdlc_register_fail[] __initdata =
908         KERN_ERR "error registering line discipline: %d\n";
909 static char hdlc_init_fail[] __initdata =
910         KERN_INFO "N_HDLC: init failure %d\n";
911
912 static int __init n_hdlc_init(void)
913 {
914         int status;
915
916         /* range check maxframe arg */
917         if (maxframe < 4096)
918                 maxframe = 4096;
919         else if (maxframe > 65535)
920                 maxframe = 65535;
921
922         printk(hdlc_banner, maxframe);
923
924         status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
925         if (!status)
926                 printk(hdlc_register_ok);
927         else
928                 printk(hdlc_register_fail, status);
929
930         if (status)
931                 printk(hdlc_init_fail, status);
932         return status;
933         
934 }       /* end of init_module() */
935
936 static char hdlc_unregister_ok[] __exitdata =
937         KERN_INFO "N_HDLC: line discipline unregistered\n";
938 static char hdlc_unregister_fail[] __exitdata =
939         KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
940
941 static void __exit n_hdlc_exit(void)
942 {
943         /* Release tty registration of line discipline */
944         int status = tty_unregister_ldisc(N_HDLC);
945
946         if (status)
947                 printk(hdlc_unregister_fail, status);
948         else
949                 printk(hdlc_unregister_ok);
950 }
951
952 module_init(n_hdlc_init);
953 module_exit(n_hdlc_exit);
954
955 MODULE_LICENSE("GPL");
956 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
957 module_param(debuglevel, int, 0);
958 module_param(maxframe, int, 0);
959 MODULE_ALIAS_LDISC(N_HDLC);