ia64/linux-2.6.18-xen.hg

view drivers/char/n_hdlc.c @ 893:f994bfe9b93b

linux/blktap2: reduce TLB flush scope

c/s 885 added very coarse TLB flushing. Since these flushes always
follow single page updates, single page flushes (when available) are
sufficient.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
author Keir Fraser <keir.fraser@citrix.com>
date Thu Jun 04 10:32:57 2009 +0100 (2009-06-04)
parents 831230e53067
children
line source
1 /* generic HDLC line discipline for Linux
2 *
3 * Written by Paul Fulghum paulkf@microgate.com
4 * for Microgate Corporation
5 *
6 * Microgate and SyncLink are registered trademarks of Microgate Corporation
7 *
8 * Adapted from ppp.c, written by Michael Callahan <callahan@maths.ox.ac.uk>,
9 * Al Longyear <longyear@netcom.com>,
10 * Paul Mackerras <Paul.Mackerras@cs.anu.edu.au>
11 *
12 * Original release 01/11/99
13 * $Id: n_hdlc.c,v 4.8 2003/05/06 21:18:51 paulkf Exp $
14 *
15 * This code is released under the GNU General Public License (GPL)
16 *
17 * This module implements the tty line discipline N_HDLC for use with
18 * tty device drivers that support bit-synchronous HDLC communications.
19 *
20 * All HDLC data is frame oriented which means:
21 *
22 * 1. tty write calls represent one complete transmit frame of data
23 * The device driver should accept the complete frame or none of
24 * the frame (busy) in the write method. Each write call should have
25 * a byte count in the range of 2-65535 bytes (2 is min HDLC frame
26 * with 1 addr byte and 1 ctrl byte). The max byte count of 65535
27 * should include any crc bytes required. For example, when using
28 * CCITT CRC32, 4 crc bytes are required, so the maximum size frame
29 * the application may transmit is limited to 65531 bytes. For CCITT
30 * CRC16, the maximum application frame size would be 65533.
31 *
32 *
33 * 2. receive callbacks from the device driver represents
34 * one received frame. The device driver should bypass
35 * the tty flip buffer and call the line discipline receive
36 * callback directly to avoid fragmenting or concatenating
37 * multiple frames into a single receive callback.
38 *
39 * The HDLC line discipline queues the receive frames in separate
40 * buffers so complete receive frames can be returned by the
41 * tty read calls.
42 *
43 * 3. tty read calls returns an entire frame of data or nothing.
44 *
45 * 4. all send and receive data is considered raw. No processing
46 * or translation is performed by the line discipline, regardless
47 * of the tty flags
48 *
49 * 5. When line discipline is queried for the amount of receive
50 * data available (FIOC), 0 is returned if no data available,
51 * otherwise the count of the next available frame is returned.
52 * (instead of the sum of all received frame counts).
53 *
54 * These conventions allow the standard tty programming interface
55 * to be used for synchronous HDLC applications when used with
56 * this line discipline (or another line discipline that is frame
57 * oriented such as N_PPP).
58 *
59 * The SyncLink driver (synclink.c) implements both asynchronous
60 * (using standard line discipline N_TTY) and synchronous HDLC
61 * (using N_HDLC) communications, with the latter using the above
62 * conventions.
63 *
64 * This implementation is very basic and does not maintain
65 * any statistics. The main point is to enforce the raw data
66 * and frame orientation of HDLC communications.
67 *
68 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
69 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
70 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
71 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
72 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
73 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
74 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
75 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
76 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
77 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
78 * OF THE POSSIBILITY OF SUCH DAMAGE.
79 */
81 #define HDLC_MAGIC 0x239e
82 #define HDLC_VERSION "$Revision: 4.8 $"
84 #include <linux/module.h>
85 #include <linux/init.h>
86 #include <linux/kernel.h>
87 #include <linux/sched.h>
88 #include <linux/types.h>
89 #include <linux/fcntl.h>
90 #include <linux/interrupt.h>
91 #include <linux/ptrace.h>
93 #undef VERSION
94 #define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
96 #include <linux/poll.h>
97 #include <linux/in.h>
98 #include <linux/ioctl.h>
99 #include <linux/slab.h>
100 #include <linux/tty.h>
101 #include <linux/errno.h>
102 #include <linux/string.h> /* used in new tty drivers */
103 #include <linux/signal.h> /* used in new tty drivers */
104 #include <linux/if.h>
105 #include <linux/bitops.h>
107 #include <asm/system.h>
108 #include <asm/termios.h>
109 #include <asm/uaccess.h>
111 /*
112 * Buffers for individual HDLC frames
113 */
114 #define MAX_HDLC_FRAME_SIZE 65535
115 #define DEFAULT_RX_BUF_COUNT 10
116 #define MAX_RX_BUF_COUNT 60
117 #define DEFAULT_TX_BUF_COUNT 1
119 struct n_hdlc_buf {
120 struct n_hdlc_buf *link;
121 int count;
122 char buf[1];
123 };
125 #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
127 struct n_hdlc_buf_list {
128 struct n_hdlc_buf *head;
129 struct n_hdlc_buf *tail;
130 int count;
131 spinlock_t spinlock;
132 };
134 /**
135 * struct n_hdlc - per device instance data structure
136 * @magic - magic value for structure
137 * @flags - miscellaneous control flags
138 * @tty - ptr to TTY structure
139 * @backup_tty - TTY to use if tty gets closed
140 * @tbusy - reentrancy flag for tx wakeup code
141 * @woke_up - FIXME: describe this field
142 * @tbuf - currently transmitting tx buffer
143 * @tx_buf_list - list of pending transmit frame buffers
144 * @rx_buf_list - list of received frame buffers
145 * @tx_free_buf_list - list unused transmit frame buffers
146 * @rx_free_buf_list - list unused received frame buffers
147 */
148 struct n_hdlc {
149 int magic;
150 __u32 flags;
151 struct tty_struct *tty;
152 struct tty_struct *backup_tty;
153 int tbusy;
154 int woke_up;
155 struct n_hdlc_buf *tbuf;
156 struct n_hdlc_buf_list tx_buf_list;
157 struct n_hdlc_buf_list rx_buf_list;
158 struct n_hdlc_buf_list tx_free_buf_list;
159 struct n_hdlc_buf_list rx_free_buf_list;
160 };
162 /*
163 * HDLC buffer list manipulation functions
164 */
165 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list);
166 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
167 struct n_hdlc_buf *buf);
168 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
170 /* Local functions */
172 static struct n_hdlc *n_hdlc_alloc (void);
174 /* debug level can be set by insmod for debugging purposes */
175 #define DEBUG_LEVEL_INFO 1
176 static int debuglevel;
178 /* max frame size for memory allocations */
179 static int maxframe = 4096;
181 /* TTY callbacks */
183 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
184 __u8 __user *buf, size_t nr);
185 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
186 const unsigned char *buf, size_t nr);
187 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
188 unsigned int cmd, unsigned long arg);
189 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
190 poll_table *wait);
191 static int n_hdlc_tty_open(struct tty_struct *tty);
192 static void n_hdlc_tty_close(struct tty_struct *tty);
193 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
194 char *fp, int count);
195 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
197 #define bset(p,b) ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
199 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
200 #define n_hdlc2tty(n_hdlc) ((n_hdlc)->tty)
202 static struct tty_ldisc n_hdlc_ldisc = {
203 .owner = THIS_MODULE,
204 .magic = TTY_LDISC_MAGIC,
205 .name = "hdlc",
206 .open = n_hdlc_tty_open,
207 .close = n_hdlc_tty_close,
208 .read = n_hdlc_tty_read,
209 .write = n_hdlc_tty_write,
210 .ioctl = n_hdlc_tty_ioctl,
211 .poll = n_hdlc_tty_poll,
212 .receive_buf = n_hdlc_tty_receive,
213 .write_wakeup = n_hdlc_tty_wakeup,
214 };
216 /**
217 * n_hdlc_release - release an n_hdlc per device line discipline info structure
218 * @n_hdlc - per device line discipline info structure
219 */
220 static void n_hdlc_release(struct n_hdlc *n_hdlc)
221 {
222 struct tty_struct *tty = n_hdlc2tty (n_hdlc);
223 struct n_hdlc_buf *buf;
225 if (debuglevel >= DEBUG_LEVEL_INFO)
226 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
228 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
229 wake_up_interruptible (&tty->read_wait);
230 wake_up_interruptible (&tty->write_wait);
232 if (tty != NULL && tty->disc_data == n_hdlc)
233 tty->disc_data = NULL; /* Break the tty->n_hdlc link */
235 /* Release transmit and receive buffers */
236 for(;;) {
237 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
238 if (buf) {
239 kfree(buf);
240 } else
241 break;
242 }
243 for(;;) {
244 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
245 if (buf) {
246 kfree(buf);
247 } else
248 break;
249 }
250 for(;;) {
251 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
252 if (buf) {
253 kfree(buf);
254 } else
255 break;
256 }
257 for(;;) {
258 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
259 if (buf) {
260 kfree(buf);
261 } else
262 break;
263 }
264 kfree(n_hdlc->tbuf);
265 kfree(n_hdlc);
267 } /* end of n_hdlc_release() */
269 /**
270 * n_hdlc_tty_close - line discipline close
271 * @tty - pointer to tty info structure
272 *
273 * Called when the line discipline is changed to something
274 * else, the tty is closed, or the tty detects a hangup.
275 */
276 static void n_hdlc_tty_close(struct tty_struct *tty)
277 {
278 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
280 if (debuglevel >= DEBUG_LEVEL_INFO)
281 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
283 if (n_hdlc != NULL) {
284 if (n_hdlc->magic != HDLC_MAGIC) {
285 printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
286 return;
287 }
288 #if defined(TTY_NO_WRITE_SPLIT)
289 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
290 #endif
291 tty->disc_data = NULL;
292 if (tty == n_hdlc->backup_tty)
293 n_hdlc->backup_tty = NULL;
294 if (tty != n_hdlc->tty)
295 return;
296 if (n_hdlc->backup_tty) {
297 n_hdlc->tty = n_hdlc->backup_tty;
298 } else {
299 n_hdlc_release (n_hdlc);
300 }
301 }
303 if (debuglevel >= DEBUG_LEVEL_INFO)
304 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
306 } /* end of n_hdlc_tty_close() */
308 /**
309 * n_hdlc_tty_open - called when line discipline changed to n_hdlc
310 * @tty - pointer to tty info structure
311 *
312 * Returns 0 if success, otherwise error code
313 */
314 static int n_hdlc_tty_open (struct tty_struct *tty)
315 {
316 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
318 if (debuglevel >= DEBUG_LEVEL_INFO)
319 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
320 __FILE__,__LINE__,
321 tty->name);
323 /* There should not be an existing table for this slot. */
324 if (n_hdlc) {
325 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
326 return -EEXIST;
327 }
329 n_hdlc = n_hdlc_alloc();
330 if (!n_hdlc) {
331 printk (KERN_ERR "n_hdlc_alloc failed\n");
332 return -ENFILE;
333 }
335 tty->disc_data = n_hdlc;
336 n_hdlc->tty = tty;
337 tty->receive_room = 65536;
339 #if defined(TTY_NO_WRITE_SPLIT)
340 /* change tty_io write() to not split large writes into 8K chunks */
341 set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
342 #endif
344 /* Flush any pending characters in the driver and discipline. */
346 if (tty->ldisc.flush_buffer)
347 tty->ldisc.flush_buffer (tty);
349 if (tty->driver->flush_buffer)
350 tty->driver->flush_buffer (tty);
352 if (debuglevel >= DEBUG_LEVEL_INFO)
353 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
355 return 0;
357 } /* end of n_tty_hdlc_open() */
359 /**
360 * n_hdlc_send_frames - send frames on pending send buffer list
361 * @n_hdlc - pointer to ldisc instance data
362 * @tty - pointer to tty instance data
363 *
364 * Send frames on pending send buffer list until the driver does not accept a
365 * frame (busy) this function is called after adding a frame to the send buffer
366 * list and by the tty wakeup callback.
367 */
368 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
369 {
370 register int actual;
371 unsigned long flags;
372 struct n_hdlc_buf *tbuf;
374 if (debuglevel >= DEBUG_LEVEL_INFO)
375 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
376 check_again:
378 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
379 if (n_hdlc->tbusy) {
380 n_hdlc->woke_up = 1;
381 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
382 return;
383 }
384 n_hdlc->tbusy = 1;
385 n_hdlc->woke_up = 0;
386 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
388 /* get current transmit buffer or get new transmit */
389 /* buffer from list of pending transmit buffers */
391 tbuf = n_hdlc->tbuf;
392 if (!tbuf)
393 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
395 while (tbuf) {
396 if (debuglevel >= DEBUG_LEVEL_INFO)
397 printk("%s(%d)sending frame %p, count=%d\n",
398 __FILE__,__LINE__,tbuf,tbuf->count);
400 /* Send the next block of data to device */
401 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
402 actual = tty->driver->write(tty, tbuf->buf, tbuf->count);
404 /* if transmit error, throw frame away by */
405 /* pretending it was accepted by driver */
406 if (actual < 0)
407 actual = tbuf->count;
409 if (actual == tbuf->count) {
410 if (debuglevel >= DEBUG_LEVEL_INFO)
411 printk("%s(%d)frame %p completed\n",
412 __FILE__,__LINE__,tbuf);
414 /* free current transmit buffer */
415 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
417 /* this tx buffer is done */
418 n_hdlc->tbuf = NULL;
420 /* wait up sleeping writers */
421 wake_up_interruptible(&tty->write_wait);
423 /* get next pending transmit buffer */
424 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
425 } else {
426 if (debuglevel >= DEBUG_LEVEL_INFO)
427 printk("%s(%d)frame %p pending\n",
428 __FILE__,__LINE__,tbuf);
430 /* buffer not accepted by driver */
431 /* set this buffer as pending buffer */
432 n_hdlc->tbuf = tbuf;
433 break;
434 }
435 }
437 if (!tbuf)
438 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
440 /* Clear the re-entry flag */
441 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
442 n_hdlc->tbusy = 0;
443 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
445 if (n_hdlc->woke_up)
446 goto check_again;
448 if (debuglevel >= DEBUG_LEVEL_INFO)
449 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
451 } /* end of n_hdlc_send_frames() */
453 /**
454 * n_hdlc_tty_wakeup - Callback for transmit wakeup
455 * @tty - pointer to associated tty instance data
456 *
457 * Called when low level device driver can accept more send data.
458 */
459 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
460 {
461 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
463 if (debuglevel >= DEBUG_LEVEL_INFO)
464 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
466 if (!n_hdlc)
467 return;
469 if (tty != n_hdlc->tty) {
470 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
471 return;
472 }
474 n_hdlc_send_frames (n_hdlc, tty);
476 } /* end of n_hdlc_tty_wakeup() */
478 /**
479 * n_hdlc_tty_receive - Called by tty driver when receive data is available
480 * @tty - pointer to tty instance data
481 * @data - pointer to received data
482 * @flags - pointer to flags for data
483 * @count - count of received data in bytes
484 *
485 * Called by tty low level driver when receive data is available. Data is
486 * interpreted as one HDLC frame.
487 */
488 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
489 char *flags, int count)
490 {
491 register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
492 register struct n_hdlc_buf *buf;
494 if (debuglevel >= DEBUG_LEVEL_INFO)
495 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
496 __FILE__,__LINE__, count);
498 /* This can happen if stuff comes in on the backup tty */
499 if (n_hdlc == 0 || tty != n_hdlc->tty)
500 return;
502 /* verify line is using HDLC discipline */
503 if (n_hdlc->magic != HDLC_MAGIC) {
504 printk("%s(%d) line not using HDLC discipline\n",
505 __FILE__,__LINE__);
506 return;
507 }
509 if ( count>maxframe ) {
510 if (debuglevel >= DEBUG_LEVEL_INFO)
511 printk("%s(%d) rx count>maxframesize, data discarded\n",
512 __FILE__,__LINE__);
513 return;
514 }
516 /* get a free HDLC buffer */
517 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
518 if (!buf) {
519 /* no buffers in free list, attempt to allocate another rx buffer */
520 /* unless the maximum count has been reached */
521 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
522 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
523 }
525 if (!buf) {
526 if (debuglevel >= DEBUG_LEVEL_INFO)
527 printk("%s(%d) no more rx buffers, data discarded\n",
528 __FILE__,__LINE__);
529 return;
530 }
532 /* copy received data to HDLC buffer */
533 memcpy(buf->buf,data,count);
534 buf->count=count;
536 /* add HDLC buffer to list of received frames */
537 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
539 /* wake up any blocked reads and perform async signalling */
540 wake_up_interruptible (&tty->read_wait);
541 if (n_hdlc->tty->fasync != NULL)
542 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
544 } /* end of n_hdlc_tty_receive() */
546 /**
547 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
548 * @tty - pointer to tty instance data
549 * @file - pointer to open file object
550 * @buf - pointer to returned data buffer
551 * @nr - size of returned data buffer
552 *
553 * Returns the number of bytes returned or error code.
554 */
555 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
556 __u8 __user *buf, size_t nr)
557 {
558 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
559 int ret;
560 struct n_hdlc_buf *rbuf;
562 if (debuglevel >= DEBUG_LEVEL_INFO)
563 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
565 /* Validate the pointers */
566 if (!n_hdlc)
567 return -EIO;
569 /* verify user access to buffer */
570 if (!access_ok(VERIFY_WRITE, buf, nr)) {
571 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
572 "buffer\n", __FILE__, __LINE__);
573 return -EFAULT;
574 }
576 for (;;) {
577 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
578 return -EIO;
580 n_hdlc = tty2n_hdlc (tty);
581 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
582 tty != n_hdlc->tty)
583 return 0;
585 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
586 if (rbuf)
587 break;
589 /* no data */
590 if (file->f_flags & O_NONBLOCK)
591 return -EAGAIN;
593 interruptible_sleep_on (&tty->read_wait);
594 if (signal_pending(current))
595 return -EINTR;
596 }
598 if (rbuf->count > nr)
599 /* frame too large for caller's buffer (discard frame) */
600 ret = -EOVERFLOW;
601 else {
602 /* Copy the data to the caller's buffer */
603 if (copy_to_user(buf, rbuf->buf, rbuf->count))
604 ret = -EFAULT;
605 else
606 ret = rbuf->count;
607 }
609 /* return HDLC buffer to free list unless the free list */
610 /* count has exceeded the default value, in which case the */
611 /* buffer is freed back to the OS to conserve memory */
612 if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
613 kfree(rbuf);
614 else
615 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
617 return ret;
619 } /* end of n_hdlc_tty_read() */
621 /**
622 * n_hdlc_tty_write - write a single frame of data to device
623 * @tty - pointer to associated tty device instance data
624 * @file - pointer to file object data
625 * @data - pointer to transmit data (one frame)
626 * @count - size of transmit frame in bytes
627 *
628 * Returns the number of bytes written (or error code).
629 */
630 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
631 const unsigned char *data, size_t count)
632 {
633 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
634 int error = 0;
635 DECLARE_WAITQUEUE(wait, current);
636 struct n_hdlc_buf *tbuf;
638 if (debuglevel >= DEBUG_LEVEL_INFO)
639 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
640 __FILE__,__LINE__,count);
642 /* Verify pointers */
643 if (!n_hdlc)
644 return -EIO;
646 if (n_hdlc->magic != HDLC_MAGIC)
647 return -EIO;
649 /* verify frame size */
650 if (count > maxframe ) {
651 if (debuglevel & DEBUG_LEVEL_INFO)
652 printk (KERN_WARNING
653 "n_hdlc_tty_write: truncating user packet "
654 "from %lu to %d\n", (unsigned long) count,
655 maxframe );
656 count = maxframe;
657 }
659 add_wait_queue(&tty->write_wait, &wait);
660 set_current_state(TASK_INTERRUPTIBLE);
662 /* Allocate transmit buffer */
663 /* sleep until transmit buffer available */
664 while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
665 schedule();
667 n_hdlc = tty2n_hdlc (tty);
668 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
669 tty != n_hdlc->tty) {
670 printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
671 error = -EIO;
672 break;
673 }
675 if (signal_pending(current)) {
676 error = -EINTR;
677 break;
678 }
679 }
681 set_current_state(TASK_RUNNING);
682 remove_wait_queue(&tty->write_wait, &wait);
684 if (!error) {
685 /* Retrieve the user's buffer */
686 memcpy(tbuf->buf, data, count);
688 /* Send the data */
689 tbuf->count = error = count;
690 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
691 n_hdlc_send_frames(n_hdlc,tty);
692 }
694 return error;
696 } /* end of n_hdlc_tty_write() */
698 /**
699 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
700 * @tty - pointer to tty instance data
701 * @file - pointer to open file object for device
702 * @cmd - IOCTL command code
703 * @arg - argument for IOCTL call (cmd dependent)
704 *
705 * Returns command dependent result.
706 */
707 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
708 unsigned int cmd, unsigned long arg)
709 {
710 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
711 int error = 0;
712 int count;
713 unsigned long flags;
715 if (debuglevel >= DEBUG_LEVEL_INFO)
716 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
717 __FILE__,__LINE__,cmd);
719 /* Verify the status of the device */
720 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
721 return -EBADF;
723 switch (cmd) {
724 case FIONREAD:
725 /* report count of read data available */
726 /* in next available frame (if any) */
727 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
728 if (n_hdlc->rx_buf_list.head)
729 count = n_hdlc->rx_buf_list.head->count;
730 else
731 count = 0;
732 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
733 error = put_user(count, (int __user *)arg);
734 break;
736 case TIOCOUTQ:
737 /* get the pending tx byte count in the driver */
738 count = tty->driver->chars_in_buffer ?
739 tty->driver->chars_in_buffer(tty) : 0;
740 /* add size of next output frame in queue */
741 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
742 if (n_hdlc->tx_buf_list.head)
743 count += n_hdlc->tx_buf_list.head->count;
744 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
745 error = put_user(count, (int __user *)arg);
746 break;
748 default:
749 error = n_tty_ioctl (tty, file, cmd, arg);
750 break;
751 }
752 return error;
754 } /* end of n_hdlc_tty_ioctl() */
756 /**
757 * n_hdlc_tty_poll - TTY callback for poll system call
758 * @tty - pointer to tty instance data
759 * @filp - pointer to open file object for device
760 * @poll_table - wait queue for operations
761 *
762 * Determine which operations (read/write) will not block and return info
763 * to caller.
764 * Returns a bit mask containing info on which ops will not block.
765 */
766 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
767 poll_table *wait)
768 {
769 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
770 unsigned int mask = 0;
772 if (debuglevel >= DEBUG_LEVEL_INFO)
773 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
775 if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
776 /* queue current process into any wait queue that */
777 /* may awaken in the future (read and write) */
779 poll_wait(filp, &tty->read_wait, wait);
780 poll_wait(filp, &tty->write_wait, wait);
782 /* set bits for operations that won't block */
783 if(n_hdlc->rx_buf_list.head)
784 mask |= POLLIN | POLLRDNORM; /* readable */
785 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
786 mask |= POLLHUP;
787 if(tty_hung_up_p(filp))
788 mask |= POLLHUP;
789 if(n_hdlc->tx_free_buf_list.head)
790 mask |= POLLOUT | POLLWRNORM; /* writable */
791 }
792 return mask;
793 } /* end of n_hdlc_tty_poll() */
795 /**
796 * n_hdlc_alloc - allocate an n_hdlc instance data structure
797 *
798 * Returns a pointer to newly created structure if success, otherwise %NULL
799 */
800 static struct n_hdlc *n_hdlc_alloc(void)
801 {
802 struct n_hdlc_buf *buf;
803 int i;
804 struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
806 if (!n_hdlc)
807 return NULL;
809 memset(n_hdlc, 0, sizeof(*n_hdlc));
811 n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
812 n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
813 n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
814 n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
816 /* allocate free rx buffer list */
817 for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
818 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
819 if (buf)
820 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
821 else if (debuglevel >= DEBUG_LEVEL_INFO)
822 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
823 }
825 /* allocate free tx buffer list */
826 for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
827 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
828 if (buf)
829 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
830 else if (debuglevel >= DEBUG_LEVEL_INFO)
831 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
832 }
834 /* Initialize the control block */
835 n_hdlc->magic = HDLC_MAGIC;
836 n_hdlc->flags = 0;
838 return n_hdlc;
840 } /* end of n_hdlc_alloc() */
842 /**
843 * n_hdlc_buf_list_init - initialize specified HDLC buffer list
844 * @list - pointer to buffer list
845 */
846 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
847 {
848 memset(list, 0, sizeof(*list));
849 spin_lock_init(&list->spinlock);
850 } /* end of n_hdlc_buf_list_init() */
852 /**
853 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
854 * @list - pointer to buffer list
855 * @buf - pointer to buffer
856 */
857 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
858 struct n_hdlc_buf *buf)
859 {
860 unsigned long flags;
861 spin_lock_irqsave(&list->spinlock,flags);
863 buf->link=NULL;
864 if(list->tail)
865 list->tail->link = buf;
866 else
867 list->head = buf;
868 list->tail = buf;
869 (list->count)++;
871 spin_unlock_irqrestore(&list->spinlock,flags);
873 } /* end of n_hdlc_buf_put() */
875 /**
876 * n_hdlc_buf_get - remove and return an HDLC buffer from list
877 * @list - pointer to HDLC buffer list
878 *
879 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
880 * list.
881 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
882 */
883 static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
884 {
885 unsigned long flags;
886 struct n_hdlc_buf *buf;
887 spin_lock_irqsave(&list->spinlock,flags);
889 buf = list->head;
890 if (buf) {
891 list->head = buf->link;
892 (list->count)--;
893 }
894 if (!list->head)
895 list->tail = NULL;
897 spin_unlock_irqrestore(&list->spinlock,flags);
898 return buf;
900 } /* end of n_hdlc_buf_get() */
902 static char hdlc_banner[] __initdata =
903 KERN_INFO "HDLC line discipline: version " HDLC_VERSION
904 ", maxframe=%u\n";
905 static char hdlc_register_ok[] __initdata =
906 KERN_INFO "N_HDLC line discipline registered.\n";
907 static char hdlc_register_fail[] __initdata =
908 KERN_ERR "error registering line discipline: %d\n";
909 static char hdlc_init_fail[] __initdata =
910 KERN_INFO "N_HDLC: init failure %d\n";
912 static int __init n_hdlc_init(void)
913 {
914 int status;
916 /* range check maxframe arg */
917 if (maxframe < 4096)
918 maxframe = 4096;
919 else if (maxframe > 65535)
920 maxframe = 65535;
922 printk(hdlc_banner, maxframe);
924 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
925 if (!status)
926 printk(hdlc_register_ok);
927 else
928 printk(hdlc_register_fail, status);
930 if (status)
931 printk(hdlc_init_fail, status);
932 return status;
934 } /* end of init_module() */
936 static char hdlc_unregister_ok[] __exitdata =
937 KERN_INFO "N_HDLC: line discipline unregistered\n";
938 static char hdlc_unregister_fail[] __exitdata =
939 KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
941 static void __exit n_hdlc_exit(void)
942 {
943 /* Release tty registration of line discipline */
944 int status = tty_unregister_ldisc(N_HDLC);
946 if (status)
947 printk(hdlc_unregister_fail, status);
948 else
949 printk(hdlc_unregister_ok);
950 }
952 module_init(n_hdlc_init);
953 module_exit(n_hdlc_exit);
955 MODULE_LICENSE("GPL");
956 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
957 module_param(debuglevel, int, 0);
958 module_param(maxframe, int, 0);
959 MODULE_ALIAS_LDISC(N_HDLC);