1 // SPDX-License-Identifier: GPL-1.0+
2 /* generic HDLC line discipline for Linux
3 *
4 * Written by Paul Fulghum paulkf@microgate.com
5 * for Microgate Corporation
6 *
7 * Microgate and SyncLink are registered trademarks of Microgate Corporation
8 *
9 * Adapted from ppp.c, written by Michael Callahan <callahan@maths.ox.ac.uk>,
10 * Al Longyear <longyear@netcom.com>,
11 * Paul Mackerras <Paul.Mackerras@cs.anu.edu.au>
12 *
13 * Original release 01/11/99
14 *
15 * This module implements the tty line discipline N_HDLC for use with
16 * tty device drivers that support bit-synchronous HDLC communications.
17 *
18 * All HDLC data is frame oriented which means:
19 *
20 * 1. tty write calls represent one complete transmit frame of data
21 * The device driver should accept the complete frame or none of
22 * the frame (busy) in the write method. Each write call should have
23 * a byte count in the range of 2-65535 bytes (2 is min HDLC frame
24 * with 1 addr byte and 1 ctrl byte). The max byte count of 65535
25 * should include any crc bytes required. For example, when using
26 * CCITT CRC32, 4 crc bytes are required, so the maximum size frame
27 * the application may transmit is limited to 65531 bytes. For CCITT
28 * CRC16, the maximum application frame size would be 65533.
29 *
30 *
31 * 2. receive callbacks from the device driver represents
32 * one received frame. The device driver should bypass
33 * the tty flip buffer and call the line discipline receive
34 * callback directly to avoid fragmenting or concatenating
35 * multiple frames into a single receive callback.
36 *
37 * The HDLC line discipline queues the receive frames in separate
38 * buffers so complete receive frames can be returned by the
39 * tty read calls.
40 *
41 * 3. tty read calls returns an entire frame of data or nothing.
42 *
43 * 4. all send and receive data is considered raw. No processing
44 * or translation is performed by the line discipline, regardless
45 * of the tty flags
46 *
47 * 5. When line discipline is queried for the amount of receive
48 * data available (FIOC), 0 is returned if no data available,
49 * otherwise the count of the next available frame is returned.
50 * (instead of the sum of all received frame counts).
51 *
52 * These conventions allow the standard tty programming interface
53 * to be used for synchronous HDLC applications when used with
54 * this line discipline (or another line discipline that is frame
55 * oriented such as N_PPP).
56 *
57 * The SyncLink driver (synclink.c) implements both asynchronous
58 * (using standard line discipline N_TTY) and synchronous HDLC
59 * (using N_HDLC) communications, with the latter using the above
60 * conventions.
61 *
62 * This implementation is very basic and does not maintain
63 * any statistics. The main point is to enforce the raw data
64 * and frame orientation of HDLC communications.
65 *
66 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
67 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
68 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
69 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
70 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
71 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
72 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
73 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
74 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
75 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
76 * OF THE POSSIBILITY OF SUCH DAMAGE.
77 */
78
79 #define HDLC_MAGIC 0x239e
80
81 #include <linux/module.h>
82 #include <linux/init.h>
83 #include <linux/kernel.h>
84 #include <linux/sched.h>
85 #include <linux/types.h>
86 #include <linux/fcntl.h>
87 #include <linux/interrupt.h>
88 #include <linux/ptrace.h>
89
90 #include <linux/poll.h>
91 #include <linux/in.h>
92 #include <linux/ioctl.h>
93 #include <linux/slab.h>
94 #include <linux/tty.h>
95 #include <linux/errno.h>
96 #include <linux/string.h> /* used in new tty drivers */
97 #include <linux/signal.h> /* used in new tty drivers */
98 #include <linux/if.h>
99 #include <linux/bitops.h>
100
101 #include <asm/termios.h>
102 #include <linux/uaccess.h>
103
104 /*
105 * Buffers for individual HDLC frames
106 */
107 #define MAX_HDLC_FRAME_SIZE 65535
108 #define DEFAULT_RX_BUF_COUNT 10
109 #define MAX_RX_BUF_COUNT 60
110 #define DEFAULT_TX_BUF_COUNT 3
111
112 struct n_hdlc_buf {
113 struct list_head list_item;
114 int count;
115 char buf[];
116 };
117
118 struct n_hdlc_buf_list {
119 struct list_head list;
120 int count;
121 spinlock_t spinlock;
122 };
123
124 /**
125 * struct n_hdlc - per device instance data structure
126 * @magic: magic value for structure
127 * @tbusy: reentrancy flag for tx wakeup code
128 * @woke_up: tx wakeup needs to be run again as it was called while @tbusy
129 * @tx_buf_list: list of pending transmit frame buffers
130 * @rx_buf_list: list of received frame buffers
131 * @tx_free_buf_list: list unused transmit frame buffers
132 * @rx_free_buf_list: list unused received frame buffers
133 */
134 struct n_hdlc {
135 int magic;
136 bool tbusy;
137 bool woke_up;
138 struct n_hdlc_buf_list tx_buf_list;
139 struct n_hdlc_buf_list rx_buf_list;
140 struct n_hdlc_buf_list tx_free_buf_list;
141 struct n_hdlc_buf_list rx_free_buf_list;
142 };
143
144 /*
145 * HDLC buffer list manipulation functions
146 */
147 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
148 struct n_hdlc_buf *buf);
149 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
150 struct n_hdlc_buf *buf);
151 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
152
153 /* Local functions */
154
155 static struct n_hdlc *n_hdlc_alloc(void);
156
157 /* max frame size for memory allocations */
158 static int maxframe = 4096;
159
flush_rx_queue(struct tty_struct * tty)160 static void flush_rx_queue(struct tty_struct *tty)
161 {
162 struct n_hdlc *n_hdlc = tty->disc_data;
163 struct n_hdlc_buf *buf;
164
165 while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
166 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
167 }
168
flush_tx_queue(struct tty_struct * tty)169 static void flush_tx_queue(struct tty_struct *tty)
170 {
171 struct n_hdlc *n_hdlc = tty->disc_data;
172 struct n_hdlc_buf *buf;
173
174 while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
175 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
176 }
177
n_hdlc_free_buf_list(struct n_hdlc_buf_list * list)178 static void n_hdlc_free_buf_list(struct n_hdlc_buf_list *list)
179 {
180 struct n_hdlc_buf *buf;
181
182 do {
183 buf = n_hdlc_buf_get(list);
184 kfree(buf);
185 } while (buf);
186 }
187
188 /**
189 * n_hdlc_tty_close - line discipline close
190 * @tty: pointer to tty info structure
191 *
192 * Called when the line discipline is changed to something
193 * else, the tty is closed, or the tty detects a hangup.
194 */
n_hdlc_tty_close(struct tty_struct * tty)195 static void n_hdlc_tty_close(struct tty_struct *tty)
196 {
197 struct n_hdlc *n_hdlc = tty->disc_data;
198
199 if (n_hdlc->magic != HDLC_MAGIC) {
200 pr_warn("n_hdlc: trying to close unopened tty!\n");
201 return;
202 }
203 #if defined(TTY_NO_WRITE_SPLIT)
204 clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags);
205 #endif
206 tty->disc_data = NULL;
207
208 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
209 wake_up_interruptible(&tty->read_wait);
210 wake_up_interruptible(&tty->write_wait);
211
212 n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list);
213 n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list);
214 n_hdlc_free_buf_list(&n_hdlc->rx_buf_list);
215 n_hdlc_free_buf_list(&n_hdlc->tx_buf_list);
216 kfree(n_hdlc);
217 } /* end of n_hdlc_tty_close() */
218
219 /**
220 * n_hdlc_tty_open - called when line discipline changed to n_hdlc
221 * @tty: pointer to tty info structure
222 *
223 * Returns 0 if success, otherwise error code
224 */
n_hdlc_tty_open(struct tty_struct * tty)225 static int n_hdlc_tty_open(struct tty_struct *tty)
226 {
227 struct n_hdlc *n_hdlc = tty->disc_data;
228
229 pr_debug("%s() called (device=%s)\n", __func__, tty->name);
230
231 /* There should not be an existing table for this slot. */
232 if (n_hdlc) {
233 pr_err("%s: tty already associated!\n", __func__);
234 return -EEXIST;
235 }
236
237 n_hdlc = n_hdlc_alloc();
238 if (!n_hdlc) {
239 pr_err("%s: n_hdlc_alloc failed\n", __func__);
240 return -ENFILE;
241 }
242
243 tty->disc_data = n_hdlc;
244 tty->receive_room = 65536;
245
246 /* change tty_io write() to not split large writes into 8K chunks */
247 set_bit(TTY_NO_WRITE_SPLIT, &tty->flags);
248
249 /* flush receive data from driver */
250 tty_driver_flush_buffer(tty);
251
252 return 0;
253
254 } /* end of n_tty_hdlc_open() */
255
256 /**
257 * n_hdlc_send_frames - send frames on pending send buffer list
258 * @n_hdlc: pointer to ldisc instance data
259 * @tty: pointer to tty instance data
260 *
261 * Send frames on pending send buffer list until the driver does not accept a
262 * frame (busy) this function is called after adding a frame to the send buffer
263 * list and by the tty wakeup callback.
264 */
n_hdlc_send_frames(struct n_hdlc * n_hdlc,struct tty_struct * tty)265 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
266 {
267 register int actual;
268 unsigned long flags;
269 struct n_hdlc_buf *tbuf;
270
271 check_again:
272
273 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
274 if (n_hdlc->tbusy) {
275 n_hdlc->woke_up = true;
276 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
277 return;
278 }
279 n_hdlc->tbusy = true;
280 n_hdlc->woke_up = false;
281 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
282
283 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
284 while (tbuf) {
285 pr_debug("sending frame %p, count=%d\n", tbuf, tbuf->count);
286
287 /* Send the next block of data to device */
288 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
289 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
290
291 /* rollback was possible and has been done */
292 if (actual == -ERESTARTSYS) {
293 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
294 break;
295 }
296 /* if transmit error, throw frame away by */
297 /* pretending it was accepted by driver */
298 if (actual < 0)
299 actual = tbuf->count;
300
301 if (actual == tbuf->count) {
302 pr_debug("frame %p completed\n", tbuf);
303
304 /* free current transmit buffer */
305 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
306
307 /* wait up sleeping writers */
308 wake_up_interruptible(&tty->write_wait);
309
310 /* get next pending transmit buffer */
311 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
312 } else {
313 pr_debug("frame %p pending\n", tbuf);
314
315 /*
316 * the buffer was not accepted by driver,
317 * return it back into tx queue
318 */
319 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
320 break;
321 }
322 }
323
324 if (!tbuf)
325 clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
326
327 /* Clear the re-entry flag */
328 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
329 n_hdlc->tbusy = false;
330 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
331
332 if (n_hdlc->woke_up)
333 goto check_again;
334 } /* end of n_hdlc_send_frames() */
335
336 /**
337 * n_hdlc_tty_wakeup - Callback for transmit wakeup
338 * @tty: pointer to associated tty instance data
339 *
340 * Called when low level device driver can accept more send data.
341 */
n_hdlc_tty_wakeup(struct tty_struct * tty)342 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
343 {
344 struct n_hdlc *n_hdlc = tty->disc_data;
345
346 n_hdlc_send_frames(n_hdlc, tty);
347 } /* end of n_hdlc_tty_wakeup() */
348
349 /**
350 * n_hdlc_tty_receive - Called by tty driver when receive data is available
351 * @tty: pointer to tty instance data
352 * @data: pointer to received data
353 * @flags: pointer to flags for data
354 * @count: count of received data in bytes
355 *
356 * Called by tty low level driver when receive data is available. Data is
357 * interpreted as one HDLC frame.
358 */
n_hdlc_tty_receive(struct tty_struct * tty,const __u8 * data,char * flags,int count)359 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
360 char *flags, int count)
361 {
362 register struct n_hdlc *n_hdlc = tty->disc_data;
363 register struct n_hdlc_buf *buf;
364
365 pr_debug("%s() called count=%d\n", __func__, count);
366
367 /* verify line is using HDLC discipline */
368 if (n_hdlc->magic != HDLC_MAGIC) {
369 pr_err("line not using HDLC discipline\n");
370 return;
371 }
372
373 if (count > maxframe) {
374 pr_debug("rx count>maxframesize, data discarded\n");
375 return;
376 }
377
378 /* get a free HDLC buffer */
379 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
380 if (!buf) {
381 /*
382 * no buffers in free list, attempt to allocate another rx
383 * buffer unless the maximum count has been reached
384 */
385 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
386 buf = kmalloc(struct_size(buf, buf, maxframe),
387 GFP_ATOMIC);
388 }
389
390 if (!buf) {
391 pr_debug("no more rx buffers, data discarded\n");
392 return;
393 }
394
395 /* copy received data to HDLC buffer */
396 memcpy(buf->buf, data, count);
397 buf->count = count;
398
399 /* add HDLC buffer to list of received frames */
400 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
401
402 /* wake up any blocked reads and perform async signalling */
403 wake_up_interruptible(&tty->read_wait);
404 if (tty->fasync != NULL)
405 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
406
407 } /* end of n_hdlc_tty_receive() */
408
409 /**
410 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
411 * @tty: pointer to tty instance data
412 * @file: pointer to open file object
413 * @buf: pointer to returned data buffer
414 * @nr: size of returned data buffer
415 *
416 * Returns the number of bytes returned or error code.
417 */
n_hdlc_tty_read(struct tty_struct * tty,struct file * file,__u8 __user * buf,size_t nr)418 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
419 __u8 __user *buf, size_t nr)
420 {
421 struct n_hdlc *n_hdlc = tty->disc_data;
422 int ret = 0;
423 struct n_hdlc_buf *rbuf;
424 DECLARE_WAITQUEUE(wait, current);
425
426 add_wait_queue(&tty->read_wait, &wait);
427
428 for (;;) {
429 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
430 ret = -EIO;
431 break;
432 }
433 if (tty_hung_up_p(file))
434 break;
435
436 set_current_state(TASK_INTERRUPTIBLE);
437
438 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
439 if (rbuf) {
440 if (rbuf->count > nr) {
441 /* too large for caller's buffer */
442 ret = -EOVERFLOW;
443 } else {
444 __set_current_state(TASK_RUNNING);
445 if (copy_to_user(buf, rbuf->buf, rbuf->count))
446 ret = -EFAULT;
447 else
448 ret = rbuf->count;
449 }
450
451 if (n_hdlc->rx_free_buf_list.count >
452 DEFAULT_RX_BUF_COUNT)
453 kfree(rbuf);
454 else
455 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
456 break;
457 }
458
459 /* no data */
460 if (tty_io_nonblock(tty, file)) {
461 ret = -EAGAIN;
462 break;
463 }
464
465 schedule();
466
467 if (signal_pending(current)) {
468 ret = -EINTR;
469 break;
470 }
471 }
472
473 remove_wait_queue(&tty->read_wait, &wait);
474 __set_current_state(TASK_RUNNING);
475
476 return ret;
477
478 } /* end of n_hdlc_tty_read() */
479
480 /**
481 * n_hdlc_tty_write - write a single frame of data to device
482 * @tty: pointer to associated tty device instance data
483 * @file: pointer to file object data
484 * @data: pointer to transmit data (one frame)
485 * @count: size of transmit frame in bytes
486 *
487 * Returns the number of bytes written (or error code).
488 */
n_hdlc_tty_write(struct tty_struct * tty,struct file * file,const unsigned char * data,size_t count)489 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
490 const unsigned char *data, size_t count)
491 {
492 struct n_hdlc *n_hdlc = tty->disc_data;
493 int error = 0;
494 DECLARE_WAITQUEUE(wait, current);
495 struct n_hdlc_buf *tbuf;
496
497 pr_debug("%s() called count=%zd\n", __func__, count);
498
499 if (n_hdlc->magic != HDLC_MAGIC)
500 return -EIO;
501
502 /* verify frame size */
503 if (count > maxframe) {
504 pr_debug("%s: truncating user packet from %zu to %d\n",
505 __func__, count, maxframe);
506 count = maxframe;
507 }
508
509 add_wait_queue(&tty->write_wait, &wait);
510
511 for (;;) {
512 set_current_state(TASK_INTERRUPTIBLE);
513
514 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
515 if (tbuf)
516 break;
517
518 if (tty_io_nonblock(tty, file)) {
519 error = -EAGAIN;
520 break;
521 }
522 schedule();
523
524 if (signal_pending(current)) {
525 error = -EINTR;
526 break;
527 }
528 }
529
530 __set_current_state(TASK_RUNNING);
531 remove_wait_queue(&tty->write_wait, &wait);
532
533 if (!error) {
534 /* Retrieve the user's buffer */
535 memcpy(tbuf->buf, data, count);
536
537 /* Send the data */
538 tbuf->count = error = count;
539 n_hdlc_buf_put(&n_hdlc->tx_buf_list, tbuf);
540 n_hdlc_send_frames(n_hdlc, tty);
541 }
542
543 return error;
544
545 } /* end of n_hdlc_tty_write() */
546
547 /**
548 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
549 * @tty: pointer to tty instance data
550 * @file: pointer to open file object for device
551 * @cmd: IOCTL command code
552 * @arg: argument for IOCTL call (cmd dependent)
553 *
554 * Returns command dependent result.
555 */
n_hdlc_tty_ioctl(struct tty_struct * tty,struct file * file,unsigned int cmd,unsigned long arg)556 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
557 unsigned int cmd, unsigned long arg)
558 {
559 struct n_hdlc *n_hdlc = tty->disc_data;
560 int error = 0;
561 int count;
562 unsigned long flags;
563 struct n_hdlc_buf *buf = NULL;
564
565 pr_debug("%s() called %d\n", __func__, cmd);
566
567 /* Verify the status of the device */
568 if (n_hdlc->magic != HDLC_MAGIC)
569 return -EBADF;
570
571 switch (cmd) {
572 case FIONREAD:
573 /* report count of read data available */
574 /* in next available frame (if any) */
575 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags);
576 buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
577 struct n_hdlc_buf, list_item);
578 if (buf)
579 count = buf->count;
580 else
581 count = 0;
582 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags);
583 error = put_user(count, (int __user *)arg);
584 break;
585
586 case TIOCOUTQ:
587 /* get the pending tx byte count in the driver */
588 count = tty_chars_in_buffer(tty);
589 /* add size of next output frame in queue */
590 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
591 buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
592 struct n_hdlc_buf, list_item);
593 if (buf)
594 count += buf->count;
595 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
596 error = put_user(count, (int __user *)arg);
597 break;
598
599 case TCFLSH:
600 switch (arg) {
601 case TCIOFLUSH:
602 case TCOFLUSH:
603 flush_tx_queue(tty);
604 }
605 fallthrough; /* to default */
606
607 default:
608 error = n_tty_ioctl_helper(tty, file, cmd, arg);
609 break;
610 }
611 return error;
612
613 } /* end of n_hdlc_tty_ioctl() */
614
615 /**
616 * n_hdlc_tty_poll - TTY callback for poll system call
617 * @tty: pointer to tty instance data
618 * @filp: pointer to open file object for device
619 * @wait: wait queue for operations
620 *
621 * Determine which operations (read/write) will not block and return info
622 * to caller.
623 * Returns a bit mask containing info on which ops will not block.
624 */
n_hdlc_tty_poll(struct tty_struct * tty,struct file * filp,poll_table * wait)625 static __poll_t n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
626 poll_table *wait)
627 {
628 struct n_hdlc *n_hdlc = tty->disc_data;
629 __poll_t mask = 0;
630
631 if (n_hdlc->magic != HDLC_MAGIC)
632 return 0;
633
634 /*
635 * queue the current process into any wait queue that may awaken in the
636 * future (read and write)
637 */
638 poll_wait(filp, &tty->read_wait, wait);
639 poll_wait(filp, &tty->write_wait, wait);
640
641 /* set bits for operations that won't block */
642 if (!list_empty(&n_hdlc->rx_buf_list.list))
643 mask |= EPOLLIN | EPOLLRDNORM; /* readable */
644 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
645 mask |= EPOLLHUP;
646 if (tty_hung_up_p(filp))
647 mask |= EPOLLHUP;
648 if (!tty_is_writelocked(tty) &&
649 !list_empty(&n_hdlc->tx_free_buf_list.list))
650 mask |= EPOLLOUT | EPOLLWRNORM; /* writable */
651
652 return mask;
653 } /* end of n_hdlc_tty_poll() */
654
n_hdlc_alloc_buf(struct n_hdlc_buf_list * list,unsigned int count,const char * name)655 static void n_hdlc_alloc_buf(struct n_hdlc_buf_list *list, unsigned int count,
656 const char *name)
657 {
658 struct n_hdlc_buf *buf;
659 unsigned int i;
660
661 for (i = 0; i < count; i++) {
662 buf = kmalloc(struct_size(buf, buf, maxframe), GFP_KERNEL);
663 if (!buf) {
664 pr_debug("%s(), kmalloc() failed for %s buffer %u\n",
665 __func__, name, i);
666 return;
667 }
668 n_hdlc_buf_put(list, buf);
669 }
670 }
671
672 /**
673 * n_hdlc_alloc - allocate an n_hdlc instance data structure
674 *
675 * Returns a pointer to newly created structure if success, otherwise %NULL
676 */
n_hdlc_alloc(void)677 static struct n_hdlc *n_hdlc_alloc(void)
678 {
679 struct n_hdlc *n_hdlc = kzalloc(sizeof(*n_hdlc), GFP_KERNEL);
680
681 if (!n_hdlc)
682 return NULL;
683
684 spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);
685 spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
686 spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
687 spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
688
689 INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);
690 INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);
691 INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);
692 INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);
693
694 n_hdlc_alloc_buf(&n_hdlc->rx_free_buf_list, DEFAULT_RX_BUF_COUNT, "rx");
695 n_hdlc_alloc_buf(&n_hdlc->tx_free_buf_list, DEFAULT_TX_BUF_COUNT, "tx");
696
697 /* Initialize the control block */
698 n_hdlc->magic = HDLC_MAGIC;
699
700 return n_hdlc;
701
702 } /* end of n_hdlc_alloc() */
703
704 /**
705 * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
706 * @buf_list: pointer to the buffer list
707 * @buf: pointer to the buffer
708 */
n_hdlc_buf_return(struct n_hdlc_buf_list * buf_list,struct n_hdlc_buf * buf)709 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
710 struct n_hdlc_buf *buf)
711 {
712 unsigned long flags;
713
714 spin_lock_irqsave(&buf_list->spinlock, flags);
715
716 list_add(&buf->list_item, &buf_list->list);
717 buf_list->count++;
718
719 spin_unlock_irqrestore(&buf_list->spinlock, flags);
720 }
721
722 /**
723 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
724 * @buf_list: pointer to buffer list
725 * @buf: pointer to buffer
726 */
n_hdlc_buf_put(struct n_hdlc_buf_list * buf_list,struct n_hdlc_buf * buf)727 static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
728 struct n_hdlc_buf *buf)
729 {
730 unsigned long flags;
731
732 spin_lock_irqsave(&buf_list->spinlock, flags);
733
734 list_add_tail(&buf->list_item, &buf_list->list);
735 buf_list->count++;
736
737 spin_unlock_irqrestore(&buf_list->spinlock, flags);
738 } /* end of n_hdlc_buf_put() */
739
740 /**
741 * n_hdlc_buf_get - remove and return an HDLC buffer from list
742 * @buf_list: pointer to HDLC buffer list
743 *
744 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
745 * list.
746 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
747 */
n_hdlc_buf_get(struct n_hdlc_buf_list * buf_list)748 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
749 {
750 unsigned long flags;
751 struct n_hdlc_buf *buf;
752
753 spin_lock_irqsave(&buf_list->spinlock, flags);
754
755 buf = list_first_entry_or_null(&buf_list->list,
756 struct n_hdlc_buf, list_item);
757 if (buf) {
758 list_del(&buf->list_item);
759 buf_list->count--;
760 }
761
762 spin_unlock_irqrestore(&buf_list->spinlock, flags);
763 return buf;
764 } /* end of n_hdlc_buf_get() */
765
766 static struct tty_ldisc_ops n_hdlc_ldisc = {
767 .owner = THIS_MODULE,
768 .magic = TTY_LDISC_MAGIC,
769 .name = "hdlc",
770 .open = n_hdlc_tty_open,
771 .close = n_hdlc_tty_close,
772 .read = n_hdlc_tty_read,
773 .write = n_hdlc_tty_write,
774 .ioctl = n_hdlc_tty_ioctl,
775 .poll = n_hdlc_tty_poll,
776 .receive_buf = n_hdlc_tty_receive,
777 .write_wakeup = n_hdlc_tty_wakeup,
778 .flush_buffer = flush_rx_queue,
779 };
780
n_hdlc_init(void)781 static int __init n_hdlc_init(void)
782 {
783 int status;
784
785 /* range check maxframe arg */
786 maxframe = clamp(maxframe, 4096, MAX_HDLC_FRAME_SIZE);
787
788 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
789 if (!status)
790 pr_info("N_HDLC line discipline registered with maxframe=%d\n",
791 maxframe);
792 else
793 pr_err("N_HDLC: error registering line discipline: %d\n",
794 status);
795
796 return status;
797
798 } /* end of init_module() */
799
n_hdlc_exit(void)800 static void __exit n_hdlc_exit(void)
801 {
802 /* Release tty registration of line discipline */
803 int status = tty_unregister_ldisc(N_HDLC);
804
805 if (status)
806 pr_err("N_HDLC: can't unregister line discipline (err = %d)\n",
807 status);
808 else
809 pr_info("N_HDLC: line discipline unregistered\n");
810 }
811
812 module_init(n_hdlc_init);
813 module_exit(n_hdlc_exit);
814
815 MODULE_LICENSE("GPL");
816 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
817 module_param(maxframe, int, 0);
818 MODULE_ALIAS_LDISC(N_HDLC);
819
