source: src/linux/universal/linux-4.9/drivers/tty/n_hdlc.c @ 31662

Last change on this file since 31662 was 31662, checked in by brainslayer, 3 months ago

use new squashfs in all kernels

File size: 27.2 KB
Line 
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
116struct n_hdlc_buf {
117        struct list_head  list_item;
118        int               count;
119        char              buf[1];
120};
121
122#define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
123
124struct n_hdlc_buf_list {
125        struct list_head  list;
126        int               count;
127        spinlock_t        spinlock;
128};
129
130/**
131 * struct n_hdlc - per device instance data structure
132 * @magic - magic value for structure
133 * @flags - miscellaneous control flags
134 * @tty - ptr to TTY structure
135 * @backup_tty - TTY to use if tty gets closed
136 * @tbusy - reentrancy flag for tx wakeup code
137 * @woke_up - FIXME: describe this field
138 * @tx_buf_list - list of pending transmit frame buffers
139 * @rx_buf_list - list of received frame buffers
140 * @tx_free_buf_list - list unused transmit frame buffers
141 * @rx_free_buf_list - list unused received frame buffers
142 */
143struct n_hdlc {
144        int                     magic;
145        __u32                   flags;
146        struct tty_struct       *tty;
147        struct tty_struct       *backup_tty;
148        int                     tbusy;
149        int                     woke_up;
150        struct n_hdlc_buf_list  tx_buf_list;
151        struct n_hdlc_buf_list  rx_buf_list;
152        struct n_hdlc_buf_list  tx_free_buf_list;
153        struct n_hdlc_buf_list  rx_free_buf_list;
154};
155
156/*
157 * HDLC buffer list manipulation functions
158 */
159static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
160                                                struct n_hdlc_buf *buf);
161static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
162                           struct n_hdlc_buf *buf);
163static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
164
165/* Local functions */
166
167static struct n_hdlc *n_hdlc_alloc (void);
168
169/* debug level can be set by insmod for debugging purposes */
170#define DEBUG_LEVEL_INFO        1
171static int debuglevel;
172
173/* max frame size for memory allocations */
174static int maxframe = 4096;
175
176/* TTY callbacks */
177
178static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
179                           __u8 __user *buf, size_t nr);
180static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
181                            const unsigned char *buf, size_t nr);
182static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
183                            unsigned int cmd, unsigned long arg);
184static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
185                                    poll_table *wait);
186static int n_hdlc_tty_open(struct tty_struct *tty);
187static void n_hdlc_tty_close(struct tty_struct *tty);
188static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
189                               char *fp, int count);
190static void n_hdlc_tty_wakeup(struct tty_struct *tty);
191
192#define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
193
194#define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
195#define n_hdlc2tty(n_hdlc)      ((n_hdlc)->tty)
196
197static void flush_rx_queue(struct tty_struct *tty)
198{
199        struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
200        struct n_hdlc_buf *buf;
201
202        while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
203                n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
204}
205
206static void flush_tx_queue(struct tty_struct *tty)
207{
208        struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
209        struct n_hdlc_buf *buf;
210
211        while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
212                n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
213}
214
215static struct tty_ldisc_ops n_hdlc_ldisc = {
216        .owner          = THIS_MODULE,
217        .magic          = TTY_LDISC_MAGIC,
218        .name           = "hdlc",
219        .open           = n_hdlc_tty_open,
220        .close          = n_hdlc_tty_close,
221        .read           = n_hdlc_tty_read,
222        .write          = n_hdlc_tty_write,
223        .ioctl          = n_hdlc_tty_ioctl,
224        .poll           = n_hdlc_tty_poll,
225        .receive_buf    = n_hdlc_tty_receive,
226        .write_wakeup   = n_hdlc_tty_wakeup,
227        .flush_buffer   = flush_rx_queue,
228};
229
230/**
231 * n_hdlc_release - release an n_hdlc per device line discipline info structure
232 * @n_hdlc - per device line discipline info structure
233 */
234static void n_hdlc_release(struct n_hdlc *n_hdlc)
235{
236        struct tty_struct *tty = n_hdlc2tty (n_hdlc);
237        struct n_hdlc_buf *buf;
238       
239        if (debuglevel >= DEBUG_LEVEL_INFO)     
240                printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
241               
242        /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
243        wake_up_interruptible (&tty->read_wait);
244        wake_up_interruptible (&tty->write_wait);
245
246        if (tty->disc_data == n_hdlc)
247                tty->disc_data = NULL;  /* Break the tty->n_hdlc link */
248
249        /* Release transmit and receive buffers */
250        for(;;) {
251                buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
252                if (buf) {
253                        kfree(buf);
254                } else
255                        break;
256        }
257        for(;;) {
258                buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
259                if (buf) {
260                        kfree(buf);
261                } else
262                        break;
263        }
264        for(;;) {
265                buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
266                if (buf) {
267                        kfree(buf);
268                } else
269                        break;
270        }
271        for(;;) {
272                buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
273                if (buf) {
274                        kfree(buf);
275                } else
276                        break;
277        }
278        kfree(n_hdlc);
279       
280}       /* end of n_hdlc_release() */
281
282/**
283 * n_hdlc_tty_close - line discipline close
284 * @tty - pointer to tty info structure
285 *
286 * Called when the line discipline is changed to something
287 * else, the tty is closed, or the tty detects a hangup.
288 */
289static void n_hdlc_tty_close(struct tty_struct *tty)
290{
291        struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
292
293        if (debuglevel >= DEBUG_LEVEL_INFO)     
294                printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
295               
296        if (n_hdlc != NULL) {
297                if (n_hdlc->magic != HDLC_MAGIC) {
298                        printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
299                        return;
300                }
301#if defined(TTY_NO_WRITE_SPLIT)
302                clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
303#endif
304                tty->disc_data = NULL;
305                if (tty == n_hdlc->backup_tty)
306                        n_hdlc->backup_tty = NULL;
307                if (tty != n_hdlc->tty)
308                        return;
309                if (n_hdlc->backup_tty) {
310                        n_hdlc->tty = n_hdlc->backup_tty;
311                } else {
312                        n_hdlc_release (n_hdlc);
313                }
314        }
315       
316        if (debuglevel >= DEBUG_LEVEL_INFO)     
317                printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
318               
319}       /* end of n_hdlc_tty_close() */
320
321/**
322 * n_hdlc_tty_open - called when line discipline changed to n_hdlc
323 * @tty - pointer to tty info structure
324 *
325 * Returns 0 if success, otherwise error code
326 */
327static int n_hdlc_tty_open (struct tty_struct *tty)
328{
329        struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
330
331        if (debuglevel >= DEBUG_LEVEL_INFO)     
332                printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
333                __FILE__,__LINE__,
334                tty->name);
335               
336        /* There should not be an existing table for this slot. */
337        if (n_hdlc) {
338                printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
339                return -EEXIST;
340        }
341       
342        n_hdlc = n_hdlc_alloc();
343        if (!n_hdlc) {
344                printk (KERN_ERR "n_hdlc_alloc failed\n");
345                return -ENFILE;
346        }
347               
348        tty->disc_data = n_hdlc;
349        n_hdlc->tty    = tty;
350        tty->receive_room = 65536;
351       
352#if defined(TTY_NO_WRITE_SPLIT)
353        /* change tty_io write() to not split large writes into 8K chunks */
354        set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
355#endif
356       
357        /* flush receive data from driver */
358        tty_driver_flush_buffer(tty);
359               
360        if (debuglevel >= DEBUG_LEVEL_INFO)     
361                printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
362               
363        return 0;
364       
365}       /* end of n_tty_hdlc_open() */
366
367/**
368 * n_hdlc_send_frames - send frames on pending send buffer list
369 * @n_hdlc - pointer to ldisc instance data
370 * @tty - pointer to tty instance data
371 *
372 * Send frames on pending send buffer list until the driver does not accept a
373 * frame (busy) this function is called after adding a frame to the send buffer
374 * list and by the tty wakeup callback.
375 */
376static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
377{
378        register int actual;
379        unsigned long flags;
380        struct n_hdlc_buf *tbuf;
381
382        if (debuglevel >= DEBUG_LEVEL_INFO)     
383                printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
384 check_again:
385               
386        spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
387        if (n_hdlc->tbusy) {
388                n_hdlc->woke_up = 1;
389                spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
390                return;
391        }
392        n_hdlc->tbusy = 1;
393        n_hdlc->woke_up = 0;
394        spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
395
396        tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
397        while (tbuf) {
398                if (debuglevel >= DEBUG_LEVEL_INFO)     
399                        printk("%s(%d)sending frame %p, count=%d\n",
400                                __FILE__,__LINE__,tbuf,tbuf->count);
401                       
402                /* Send the next block of data to device */
403                set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
404                actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
405
406                /* rollback was possible and has been done */
407                if (actual == -ERESTARTSYS) {
408                        n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
409                        break;
410                }
411                /* if transmit error, throw frame away by */
412                /* pretending it was accepted by driver */
413                if (actual < 0)
414                        actual = tbuf->count;
415               
416                if (actual == tbuf->count) {
417                        if (debuglevel >= DEBUG_LEVEL_INFO)     
418                                printk("%s(%d)frame %p completed\n",
419                                        __FILE__,__LINE__,tbuf);
420                                       
421                        /* free current transmit buffer */
422                        n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
423
424                        /* wait up sleeping writers */
425                        wake_up_interruptible(&tty->write_wait);
426       
427                        /* get next pending transmit buffer */
428                        tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
429                } else {
430                        if (debuglevel >= DEBUG_LEVEL_INFO)     
431                                printk("%s(%d)frame %p pending\n",
432                                        __FILE__,__LINE__,tbuf);
433
434                        /*
435                         * the buffer was not accepted by driver,
436                         * return it back into tx queue
437                         */
438                        n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
439                        break;
440                }
441        }
442       
443        if (!tbuf)
444                clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
445       
446        /* Clear the re-entry flag */
447        spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
448        n_hdlc->tbusy = 0;
449        spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
450       
451        if (n_hdlc->woke_up)
452          goto check_again;
453
454        if (debuglevel >= DEBUG_LEVEL_INFO)     
455                printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
456               
457}       /* end of n_hdlc_send_frames() */
458
459/**
460 * n_hdlc_tty_wakeup - Callback for transmit wakeup
461 * @tty - pointer to associated tty instance data
462 *
463 * Called when low level device driver can accept more send data.
464 */
465static void n_hdlc_tty_wakeup(struct tty_struct *tty)
466{
467        struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
468
469        if (debuglevel >= DEBUG_LEVEL_INFO)     
470                printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
471               
472        if (!n_hdlc)
473                return;
474
475        if (tty != n_hdlc->tty) {
476                clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
477                return;
478        }
479
480        n_hdlc_send_frames (n_hdlc, tty);
481               
482}       /* end of n_hdlc_tty_wakeup() */
483
484/**
485 * n_hdlc_tty_receive - Called by tty driver when receive data is available
486 * @tty - pointer to tty instance data
487 * @data - pointer to received data
488 * @flags - pointer to flags for data
489 * @count - count of received data in bytes
490 *
491 * Called by tty low level driver when receive data is available. Data is
492 * interpreted as one HDLC frame.
493 */
494static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
495                               char *flags, int count)
496{
497        register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
498        register struct n_hdlc_buf *buf;
499
500        if (debuglevel >= DEBUG_LEVEL_INFO)     
501                printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
502                        __FILE__,__LINE__, count);
503               
504        /* This can happen if stuff comes in on the backup tty */
505        if (!n_hdlc || tty != n_hdlc->tty)
506                return;
507               
508        /* verify line is using HDLC discipline */
509        if (n_hdlc->magic != HDLC_MAGIC) {
510                printk("%s(%d) line not using HDLC discipline\n",
511                        __FILE__,__LINE__);
512                return;
513        }
514       
515        if ( count>maxframe ) {
516                if (debuglevel >= DEBUG_LEVEL_INFO)     
517                        printk("%s(%d) rx count>maxframesize, data discarded\n",
518                               __FILE__,__LINE__);
519                return;
520        }
521
522        /* get a free HDLC buffer */   
523        buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
524        if (!buf) {
525                /* no buffers in free list, attempt to allocate another rx buffer */
526                /* unless the maximum count has been reached */
527                if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
528                        buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
529        }
530       
531        if (!buf) {
532                if (debuglevel >= DEBUG_LEVEL_INFO)     
533                        printk("%s(%d) no more rx buffers, data discarded\n",
534                               __FILE__,__LINE__);
535                return;
536        }
537               
538        /* copy received data to HDLC buffer */
539        memcpy(buf->buf,data,count);
540        buf->count=count;
541
542        /* add HDLC buffer to list of received frames */
543        n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
544       
545        /* wake up any blocked reads and perform async signalling */
546        wake_up_interruptible (&tty->read_wait);
547        if (n_hdlc->tty->fasync != NULL)
548                kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
549
550}       /* end of n_hdlc_tty_receive() */
551
552/**
553 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
554 * @tty - pointer to tty instance data
555 * @file - pointer to open file object
556 * @buf - pointer to returned data buffer
557 * @nr - size of returned data buffer
558 *     
559 * Returns the number of bytes returned or error code.
560 */
561static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
562                           __u8 __user *buf, size_t nr)
563{
564        struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
565        int ret = 0;
566        struct n_hdlc_buf *rbuf;
567        DECLARE_WAITQUEUE(wait, current);
568
569        if (debuglevel >= DEBUG_LEVEL_INFO)     
570                printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
571               
572        /* Validate the pointers */
573        if (!n_hdlc)
574                return -EIO;
575
576        /* verify user access to buffer */
577        if (!access_ok(VERIFY_WRITE, buf, nr)) {
578                printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
579                "buffer\n", __FILE__, __LINE__);
580                return -EFAULT;
581        }
582
583        add_wait_queue(&tty->read_wait, &wait);
584
585        for (;;) {
586                if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
587                        ret = -EIO;
588                        break;
589                }
590                if (tty_hung_up_p(file))
591                        break;
592
593                set_current_state(TASK_INTERRUPTIBLE);
594
595                rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
596                if (rbuf) {
597                        if (rbuf->count > nr) {
598                                /* too large for caller's buffer */
599                                ret = -EOVERFLOW;
600                        } else {
601                                if (copy_to_user(buf, rbuf->buf, rbuf->count))
602                                        ret = -EFAULT;
603                                else
604                                        ret = rbuf->count;
605                        }
606
607                        if (n_hdlc->rx_free_buf_list.count >
608                            DEFAULT_RX_BUF_COUNT)
609                                kfree(rbuf);
610                        else
611                                n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
612                        break;
613                }
614                       
615                /* no data */
616                if (file->f_flags & O_NONBLOCK) {
617                        ret = -EAGAIN;
618                        break;
619                }
620
621                schedule();
622
623                if (signal_pending(current)) {
624                        ret = -EINTR;
625                        break;
626                }
627        }
628
629        remove_wait_queue(&tty->read_wait, &wait);
630        __set_current_state(TASK_RUNNING);
631
632        return ret;
633       
634}       /* end of n_hdlc_tty_read() */
635
636/**
637 * n_hdlc_tty_write - write a single frame of data to device
638 * @tty - pointer to associated tty device instance data
639 * @file - pointer to file object data
640 * @data - pointer to transmit data (one frame)
641 * @count - size of transmit frame in bytes
642 *             
643 * Returns the number of bytes written (or error code).
644 */
645static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
646                            const unsigned char *data, size_t count)
647{
648        struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
649        int error = 0;
650        DECLARE_WAITQUEUE(wait, current);
651        struct n_hdlc_buf *tbuf;
652
653        if (debuglevel >= DEBUG_LEVEL_INFO)     
654                printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
655                        __FILE__,__LINE__,count);
656               
657        /* Verify pointers */
658        if (!n_hdlc)
659                return -EIO;
660
661        if (n_hdlc->magic != HDLC_MAGIC)
662                return -EIO;
663
664        /* verify frame size */
665        if (count > maxframe ) {
666                if (debuglevel & DEBUG_LEVEL_INFO)
667                        printk (KERN_WARNING
668                                "n_hdlc_tty_write: truncating user packet "
669                                "from %lu to %d\n", (unsigned long) count,
670                                maxframe );
671                count = maxframe;
672        }
673       
674        add_wait_queue(&tty->write_wait, &wait);
675
676        for (;;) {
677                set_current_state(TASK_INTERRUPTIBLE);
678       
679                tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
680                if (tbuf)
681                        break;
682
683                if (file->f_flags & O_NONBLOCK) {
684                        error = -EAGAIN;
685                        break;
686                }
687                schedule();
688                       
689                n_hdlc = tty2n_hdlc (tty);
690                if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
691                    tty != n_hdlc->tty) {
692                        printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
693                        error = -EIO;
694                        break;
695                }
696                       
697                if (signal_pending(current)) {
698                        error = -EINTR;
699                        break;
700                }
701        }
702
703        __set_current_state(TASK_RUNNING);
704        remove_wait_queue(&tty->write_wait, &wait);
705
706        if (!error) {           
707                /* Retrieve the user's buffer */
708                memcpy(tbuf->buf, data, count);
709
710                /* Send the data */
711                tbuf->count = error = count;
712                n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
713                n_hdlc_send_frames(n_hdlc,tty);
714        }
715
716        return error;
717       
718}       /* end of n_hdlc_tty_write() */
719
720/**
721 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
722 * @tty - pointer to tty instance data
723 * @file - pointer to open file object for device
724 * @cmd - IOCTL command code
725 * @arg - argument for IOCTL call (cmd dependent)
726 *
727 * Returns command dependent result.
728 */
729static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
730                            unsigned int cmd, unsigned long arg)
731{
732        struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
733        int error = 0;
734        int count;
735        unsigned long flags;
736        struct n_hdlc_buf *buf = NULL;
737
738        if (debuglevel >= DEBUG_LEVEL_INFO)     
739                printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
740                        __FILE__,__LINE__,cmd);
741               
742        /* Verify the status of the device */
743        if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
744                return -EBADF;
745
746        switch (cmd) {
747        case FIONREAD:
748                /* report count of read data available */
749                /* in next available frame (if any) */
750                spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
751                buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
752                                                struct n_hdlc_buf, list_item);
753                if (buf)
754                        count = buf->count;
755                else
756                        count = 0;
757                spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
758                error = put_user(count, (int __user *)arg);
759                break;
760
761        case TIOCOUTQ:
762                /* get the pending tx byte count in the driver */
763                count = tty_chars_in_buffer(tty);
764                /* add size of next output frame in queue */
765                spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
766                buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
767                                                struct n_hdlc_buf, list_item);
768                if (buf)
769                        count += buf->count;
770                spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
771                error = put_user(count, (int __user *)arg);
772                break;
773
774        case TCFLSH:
775                switch (arg) {
776                case TCIOFLUSH:
777                case TCOFLUSH:
778                        flush_tx_queue(tty);
779                }
780                /* fall through to default */
781
782        default:
783                error = n_tty_ioctl_helper(tty, file, cmd, arg);
784                break;
785        }
786        return error;
787       
788}       /* end of n_hdlc_tty_ioctl() */
789
790/**
791 * n_hdlc_tty_poll - TTY callback for poll system call
792 * @tty - pointer to tty instance data
793 * @filp - pointer to open file object for device
794 * @poll_table - wait queue for operations
795 *
796 * Determine which operations (read/write) will not block and return info
797 * to caller.
798 * Returns a bit mask containing info on which ops will not block.
799 */
800static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
801                                    poll_table *wait)
802{
803        struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
804        unsigned int mask = 0;
805
806        if (debuglevel >= DEBUG_LEVEL_INFO)     
807                printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
808               
809        if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
810                /* queue current process into any wait queue that */
811                /* may awaken in the future (read and write) */
812
813                poll_wait(filp, &tty->read_wait, wait);
814                poll_wait(filp, &tty->write_wait, wait);
815
816                /* set bits for operations that won't block */
817                if (!list_empty(&n_hdlc->rx_buf_list.list))
818                        mask |= POLLIN | POLLRDNORM;    /* readable */
819                if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
820                        mask |= POLLHUP;
821                if (tty_hung_up_p(filp))
822                        mask |= POLLHUP;
823                if (!tty_is_writelocked(tty) &&
824                                !list_empty(&n_hdlc->tx_free_buf_list.list))
825                        mask |= POLLOUT | POLLWRNORM;   /* writable */
826        }
827        return mask;
828}       /* end of n_hdlc_tty_poll() */
829
830/**
831 * n_hdlc_alloc - allocate an n_hdlc instance data structure
832 *
833 * Returns a pointer to newly created structure if success, otherwise %NULL
834 */
835static struct n_hdlc *n_hdlc_alloc(void)
836{
837        struct n_hdlc_buf *buf;
838        int i;
839        struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL);
840
841        if (!n_hdlc)
842                return NULL;
843
844        spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);
845        spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
846        spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
847        spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
848
849        INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);
850        INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);
851        INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);
852        INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);
853
854        /* allocate free rx buffer list */
855        for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
856                buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
857                if (buf)
858                        n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
859                else if (debuglevel >= DEBUG_LEVEL_INFO)       
860                        printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
861        }
862       
863        /* allocate free tx buffer list */
864        for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
865                buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
866                if (buf)
867                        n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
868                else if (debuglevel >= DEBUG_LEVEL_INFO)       
869                        printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
870        }
871       
872        /* Initialize the control block */
873        n_hdlc->magic  = HDLC_MAGIC;
874        n_hdlc->flags  = 0;
875       
876        return n_hdlc;
877       
878}       /* end of n_hdlc_alloc() */
879
880/**
881 * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
882 * @buf_list - pointer to the buffer list
883 * @buf - pointer to the buffer
884 */
885static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
886                                                struct n_hdlc_buf *buf)
887{
888        unsigned long flags;
889
890        spin_lock_irqsave(&buf_list->spinlock, flags);
891
892        list_add(&buf->list_item, &buf_list->list);
893        buf_list->count++;
894
895        spin_unlock_irqrestore(&buf_list->spinlock, flags);
896}
897
898/**
899 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
900 * @buf_list - pointer to buffer list
901 * @buf - pointer to buffer
902 */
903static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
904                           struct n_hdlc_buf *buf)
905{
906        unsigned long flags;
907
908        spin_lock_irqsave(&buf_list->spinlock, flags);
909
910        list_add_tail(&buf->list_item, &buf_list->list);
911        buf_list->count++;
912
913        spin_unlock_irqrestore(&buf_list->spinlock, flags);
914}       /* end of n_hdlc_buf_put() */
915
916/**
917 * n_hdlc_buf_get - remove and return an HDLC buffer from list
918 * @buf_list - pointer to HDLC buffer list
919 *
920 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
921 * list.
922 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
923 */
924static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
925{
926        unsigned long flags;
927        struct n_hdlc_buf *buf;
928
929        spin_lock_irqsave(&buf_list->spinlock, flags);
930
931        buf = list_first_entry_or_null(&buf_list->list,
932                                                struct n_hdlc_buf, list_item);
933        if (buf) {
934                list_del(&buf->list_item);
935                buf_list->count--;
936        }
937
938        spin_unlock_irqrestore(&buf_list->spinlock, flags);
939        return buf;
940}       /* end of n_hdlc_buf_get() */
941
942static char hdlc_banner[] __initdata =
943        KERN_INFO "HDLC line discipline maxframe=%u\n";
944static char hdlc_register_ok[] __initdata =
945        KERN_INFO "N_HDLC line discipline registered.\n";
946static char hdlc_register_fail[] __initdata =
947        KERN_ERR "error registering line discipline: %d\n";
948
949static int __init n_hdlc_init(void)
950{
951        int status;
952
953        /* range check maxframe arg */
954        if (maxframe < 4096)
955                maxframe = 4096;
956        else if (maxframe > 65535)
957                maxframe = 65535;
958
959        printk(hdlc_banner, maxframe);
960
961        status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
962        if (!status)
963                printk(hdlc_register_ok);
964        else
965                printk(hdlc_register_fail, status);
966
967        return status;
968       
969}       /* end of init_module() */
970
971static char hdlc_unregister_ok[] __exitdata =
972        KERN_INFO "N_HDLC: line discipline unregistered\n";
973static char hdlc_unregister_fail[] __exitdata =
974        KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
975
976static void __exit n_hdlc_exit(void)
977{
978        /* Release tty registration of line discipline */
979        int status = tty_unregister_ldisc(N_HDLC);
980
981        if (status)
982                printk(hdlc_unregister_fail, status);
983        else
984                printk(hdlc_unregister_ok);
985}
986
987module_init(n_hdlc_init);
988module_exit(n_hdlc_exit);
989
990MODULE_LICENSE("GPL");
991MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
992module_param(debuglevel, int, 0);
993module_param(maxframe, int, 0);
994MODULE_ALIAS_LDISC(N_HDLC);
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