Root/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
116struct 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
124struct 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 */
145struct 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 */
162static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list);
163static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
164               struct n_hdlc_buf *buf);
165static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
166
167/* Local functions */
168
169static 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
173static int debuglevel;
174
175/* max frame size for memory allocations */
176static int maxframe = 4096;
177
178/* TTY callbacks */
179
180static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
181               __u8 __user *buf, size_t nr);
182static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
183                const unsigned char *buf, size_t nr);
184static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
185                unsigned int cmd, unsigned long arg);
186static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
187                    poll_table *wait);
188static int n_hdlc_tty_open(struct tty_struct *tty);
189static void n_hdlc_tty_close(struct tty_struct *tty);
190static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
191                   char *fp, int count);
192static 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
199static 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
208static 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
224static 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 */
243static 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 */
299static 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 */
337static 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 */
386static 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 */
482static 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 */
511static 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 */
578static 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 */
662static 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 */
746static 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 */
812static 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 */
847static 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 */
893static 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 */
904static 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 */
930static 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
949static char hdlc_banner[] __initdata =
950    KERN_INFO "HDLC line discipline maxframe=%u\n";
951static char hdlc_register_ok[] __initdata =
952    KERN_INFO "N_HDLC line discipline registered.\n";
953static char hdlc_register_fail[] __initdata =
954    KERN_ERR "error registering line discipline: %d\n";
955static char hdlc_init_fail[] __initdata =
956    KERN_INFO "N_HDLC: init failure %d\n";
957
958static 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
982static char hdlc_unregister_ok[] __exitdata =
983    KERN_INFO "N_HDLC: line discipline unregistered\n";
984static char hdlc_unregister_fail[] __exitdata =
985    KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
986
987static 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
998module_init(n_hdlc_init);
999module_exit(n_hdlc_exit);
1000
1001MODULE_LICENSE("GPL");
1002MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
1003module_param(debuglevel, int, 0);
1004module_param(maxframe, int, 0);
1005MODULE_ALIAS_LDISC(N_HDLC);
1006

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