1 /* generic HDLC line discipline for Linux
3 * Written by Paul Fulghum paulkf@microgate.com
4 * for Microgate Corporation
6 * Microgate and SyncLink are registered trademarks of Microgate Corporation
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>
12 * Original release 01/11/99
14 * This code is released under the GNU General Public License (GPL)
16 * This module implements the tty line discipline N_HDLC for use with
17 * tty device drivers that support bit-synchronous HDLC communications.
19 * All HDLC data is frame oriented which means:
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.
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.
38 * The HDLC line discipline queues the receive frames in separate
39 * buffers so complete receive frames can be returned by the
42 * 3. tty read calls returns an entire frame of data or nothing.
44 * 4. all send and receive data is considered raw. No processing
45 * or translation is performed by the line discipline, regardless
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).
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).
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
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.
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.
80 #define HDLC_MAGIC 0x239e
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>
92 #define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
94 #include <linux/poll.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>
105 #include <asm/system.h>
106 #include <asm/termios.h>
107 #include <asm/uaccess.h>
110 * Buffers for individual HDLC frames
112 #define MAX_HDLC_FRAME_SIZE 65535
113 #define DEFAULT_RX_BUF_COUNT 10
114 #define MAX_RX_BUF_COUNT 60
115 #define DEFAULT_TX_BUF_COUNT 3
118 struct list_head list_item;
123 #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
125 struct n_hdlc_buf_list {
126 struct list_head list;
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 * @tx_buf_list - list of pending transmit frame buffers
140 * @rx_buf_list - list of received frame buffers
141 * @tx_free_buf_list - list unused transmit frame buffers
142 * @rx_free_buf_list - list unused received frame buffers
147 struct tty_struct *tty;
148 struct tty_struct *backup_tty;
151 struct n_hdlc_buf_list tx_buf_list;
152 struct n_hdlc_buf_list rx_buf_list;
153 struct n_hdlc_buf_list tx_free_buf_list;
154 struct n_hdlc_buf_list rx_free_buf_list;
158 * HDLC buffer list manipulation functions
160 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
161 struct n_hdlc_buf *buf);
162 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
163 struct n_hdlc_buf *buf);
164 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
166 /* Local functions */
168 static struct n_hdlc *n_hdlc_alloc (void);
170 /* debug level can be set by insmod for debugging purposes */
171 #define DEBUG_LEVEL_INFO 1
172 static int debuglevel;
174 /* max frame size for memory allocations */
175 static int maxframe = 4096;
179 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
180 __u8 __user *buf, size_t nr);
181 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
182 const unsigned char *buf, size_t nr);
183 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
184 unsigned int cmd, unsigned long arg);
185 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
187 static int n_hdlc_tty_open(struct tty_struct *tty);
188 static void n_hdlc_tty_close(struct tty_struct *tty);
189 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
190 char *fp, int count);
191 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
193 #define bset(p,b) ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
195 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
196 #define n_hdlc2tty(n_hdlc) ((n_hdlc)->tty)
198 static void flush_rx_queue(struct tty_struct *tty)
200 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
201 struct n_hdlc_buf *buf;
203 while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
204 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
207 static void flush_tx_queue(struct tty_struct *tty)
209 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
210 struct n_hdlc_buf *buf;
212 while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
213 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
216 static struct tty_ldisc_ops n_hdlc_ldisc = {
217 .owner = THIS_MODULE,
218 .magic = TTY_LDISC_MAGIC,
220 .open = n_hdlc_tty_open,
221 .close = n_hdlc_tty_close,
222 .read = n_hdlc_tty_read,
223 .write = n_hdlc_tty_write,
224 .ioctl = n_hdlc_tty_ioctl,
225 .poll = n_hdlc_tty_poll,
226 .receive_buf = n_hdlc_tty_receive,
227 .write_wakeup = n_hdlc_tty_wakeup,
228 .flush_buffer = flush_rx_queue,
232 * n_hdlc_release - release an n_hdlc per device line discipline info structure
233 * @n_hdlc - per device line discipline info structure
235 static void n_hdlc_release(struct n_hdlc *n_hdlc)
237 struct tty_struct *tty = n_hdlc2tty (n_hdlc);
238 struct n_hdlc_buf *buf;
240 if (debuglevel >= DEBUG_LEVEL_INFO)
241 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
243 /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
244 wake_up_interruptible (&tty->read_wait);
245 wake_up_interruptible (&tty->write_wait);
247 if (tty->disc_data == n_hdlc)
248 tty->disc_data = NULL; /* Break the tty->n_hdlc link */
250 /* Release transmit and receive buffers */
252 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
259 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
266 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
273 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
281 } /* end of n_hdlc_release() */
284 * n_hdlc_tty_close - line discipline close
285 * @tty - pointer to tty info structure
287 * Called when the line discipline is changed to something
288 * else, the tty is closed, or the tty detects a hangup.
290 static void n_hdlc_tty_close(struct tty_struct *tty)
292 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
294 if (debuglevel >= DEBUG_LEVEL_INFO)
295 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
297 if (n_hdlc != NULL) {
298 if (n_hdlc->magic != HDLC_MAGIC) {
299 printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
302 #if defined(TTY_NO_WRITE_SPLIT)
303 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
305 tty->disc_data = NULL;
306 if (tty == n_hdlc->backup_tty)
307 n_hdlc->backup_tty = NULL;
308 if (tty != n_hdlc->tty)
310 if (n_hdlc->backup_tty) {
311 n_hdlc->tty = n_hdlc->backup_tty;
313 n_hdlc_release (n_hdlc);
317 if (debuglevel >= DEBUG_LEVEL_INFO)
318 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
320 } /* end of n_hdlc_tty_close() */
323 * n_hdlc_tty_open - called when line discipline changed to n_hdlc
324 * @tty - pointer to tty info structure
326 * Returns 0 if success, otherwise error code
328 static int n_hdlc_tty_open (struct tty_struct *tty)
330 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
332 if (debuglevel >= DEBUG_LEVEL_INFO)
333 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
337 /* There should not be an existing table for this slot. */
339 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
343 n_hdlc = n_hdlc_alloc();
345 printk (KERN_ERR "n_hdlc_alloc failed\n");
349 tty->disc_data = n_hdlc;
351 tty->receive_room = 65536;
353 #if defined(TTY_NO_WRITE_SPLIT)
354 /* change tty_io write() to not split large writes into 8K chunks */
355 set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
358 /* flush receive data from driver */
359 tty_driver_flush_buffer(tty);
361 if (debuglevel >= DEBUG_LEVEL_INFO)
362 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
366 } /* end of n_tty_hdlc_open() */
369 * n_hdlc_send_frames - send frames on pending send buffer list
370 * @n_hdlc - pointer to ldisc instance data
371 * @tty - pointer to tty instance data
373 * Send frames on pending send buffer list until the driver does not accept a
374 * frame (busy) this function is called after adding a frame to the send buffer
375 * list and by the tty wakeup callback.
377 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
381 struct n_hdlc_buf *tbuf;
383 if (debuglevel >= DEBUG_LEVEL_INFO)
384 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
387 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
390 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
395 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
397 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
399 if (debuglevel >= DEBUG_LEVEL_INFO)
400 printk("%s(%d)sending frame %p, count=%d\n",
401 __FILE__,__LINE__,tbuf,tbuf->count);
403 /* Send the next block of data to device */
404 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
405 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
407 /* rollback was possible and has been done */
408 if (actual == -ERESTARTSYS) {
409 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
412 /* if transmit error, throw frame away by */
413 /* pretending it was accepted by driver */
415 actual = tbuf->count;
417 if (actual == tbuf->count) {
418 if (debuglevel >= DEBUG_LEVEL_INFO)
419 printk("%s(%d)frame %p completed\n",
420 __FILE__,__LINE__,tbuf);
422 /* free current transmit buffer */
423 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
425 /* wait up sleeping writers */
426 wake_up_interruptible(&tty->write_wait);
428 /* get next pending transmit buffer */
429 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
431 if (debuglevel >= DEBUG_LEVEL_INFO)
432 printk("%s(%d)frame %p pending\n",
433 __FILE__,__LINE__,tbuf);
436 * the buffer was not accepted by driver,
437 * return it back into tx queue
439 n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);
445 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
447 /* Clear the re-entry flag */
448 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
450 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
455 if (debuglevel >= DEBUG_LEVEL_INFO)
456 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
458 } /* end of n_hdlc_send_frames() */
461 * n_hdlc_tty_wakeup - Callback for transmit wakeup
462 * @tty - pointer to associated tty instance data
464 * Called when low level device driver can accept more send data.
466 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
468 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
470 if (debuglevel >= DEBUG_LEVEL_INFO)
471 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
476 if (tty != n_hdlc->tty) {
477 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
481 n_hdlc_send_frames (n_hdlc, tty);
483 } /* end of n_hdlc_tty_wakeup() */
486 * n_hdlc_tty_receive - Called by tty driver when receive data is available
487 * @tty - pointer to tty instance data
488 * @data - pointer to received data
489 * @flags - pointer to flags for data
490 * @count - count of received data in bytes
492 * Called by tty low level driver when receive data is available. Data is
493 * interpreted as one HDLC frame.
495 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
496 char *flags, int count)
498 register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
499 register struct n_hdlc_buf *buf;
501 if (debuglevel >= DEBUG_LEVEL_INFO)
502 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
503 __FILE__,__LINE__, count);
505 /* This can happen if stuff comes in on the backup tty */
506 if (!n_hdlc || tty != n_hdlc->tty)
509 /* verify line is using HDLC discipline */
510 if (n_hdlc->magic != HDLC_MAGIC) {
511 printk("%s(%d) line not using HDLC discipline\n",
516 if ( count>maxframe ) {
517 if (debuglevel >= DEBUG_LEVEL_INFO)
518 printk("%s(%d) rx count>maxframesize, data discarded\n",
523 /* get a free HDLC buffer */
524 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
526 /* no buffers in free list, attempt to allocate another rx buffer */
527 /* unless the maximum count has been reached */
528 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
529 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
533 if (debuglevel >= DEBUG_LEVEL_INFO)
534 printk("%s(%d) no more rx buffers, data discarded\n",
539 /* copy received data to HDLC buffer */
540 memcpy(buf->buf,data,count);
543 /* add HDLC buffer to list of received frames */
544 n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
546 /* wake up any blocked reads and perform async signalling */
547 wake_up_interruptible (&tty->read_wait);
548 if (n_hdlc->tty->fasync != NULL)
549 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
551 } /* end of n_hdlc_tty_receive() */
554 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
555 * @tty - pointer to tty instance data
556 * @file - pointer to open file object
557 * @buf - pointer to returned data buffer
558 * @nr - size of returned data buffer
560 * Returns the number of bytes returned or error code.
562 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
563 __u8 __user *buf, size_t nr)
565 struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
567 struct n_hdlc_buf *rbuf;
568 DECLARE_WAITQUEUE(wait, current);
570 if (debuglevel >= DEBUG_LEVEL_INFO)
571 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
573 /* Validate the pointers */
577 /* verify user access to buffer */
578 if (!access_ok(VERIFY_WRITE, buf, nr)) {
579 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
580 "buffer\n", __FILE__, __LINE__);
584 add_wait_queue(&tty->read_wait, &wait);
587 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
591 if (tty_hung_up_p(file))
594 set_current_state(TASK_INTERRUPTIBLE);
596 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
598 if (rbuf->count > nr) {
599 /* too large for caller's buffer */
602 if (copy_to_user(buf, rbuf->buf, rbuf->count))
608 if (n_hdlc->rx_free_buf_list.count >
609 DEFAULT_RX_BUF_COUNT)
612 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);
617 if (file->f_flags & O_NONBLOCK) {
624 if (signal_pending(current)) {
630 remove_wait_queue(&tty->read_wait, &wait);
631 __set_current_state(TASK_RUNNING);
635 } /* end of n_hdlc_tty_read() */
638 * n_hdlc_tty_write - write a single frame of data to device
639 * @tty - pointer to associated tty device instance data
640 * @file - pointer to file object data
641 * @data - pointer to transmit data (one frame)
642 * @count - size of transmit frame in bytes
644 * Returns the number of bytes written (or error code).
646 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
647 const unsigned char *data, size_t count)
649 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
651 DECLARE_WAITQUEUE(wait, current);
652 struct n_hdlc_buf *tbuf;
654 if (debuglevel >= DEBUG_LEVEL_INFO)
655 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
656 __FILE__,__LINE__,count);
658 /* Verify pointers */
662 if (n_hdlc->magic != HDLC_MAGIC)
665 /* verify frame size */
666 if (count > maxframe ) {
667 if (debuglevel & DEBUG_LEVEL_INFO)
669 "n_hdlc_tty_write: truncating user packet "
670 "from %lu to %d\n", (unsigned long) count,
675 add_wait_queue(&tty->write_wait, &wait);
678 set_current_state(TASK_INTERRUPTIBLE);
680 tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
684 if (file->f_flags & O_NONBLOCK) {
690 n_hdlc = tty2n_hdlc (tty);
691 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
692 tty != n_hdlc->tty) {
693 printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
698 if (signal_pending(current)) {
704 __set_current_state(TASK_RUNNING);
705 remove_wait_queue(&tty->write_wait, &wait);
708 /* Retrieve the user's buffer */
709 memcpy(tbuf->buf, data, count);
712 tbuf->count = error = count;
713 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
714 n_hdlc_send_frames(n_hdlc,tty);
719 } /* end of n_hdlc_tty_write() */
722 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
723 * @tty - pointer to tty instance data
724 * @file - pointer to open file object for device
725 * @cmd - IOCTL command code
726 * @arg - argument for IOCTL call (cmd dependent)
728 * Returns command dependent result.
730 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
731 unsigned int cmd, unsigned long arg)
733 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
737 struct n_hdlc_buf *buf = NULL;
739 if (debuglevel >= DEBUG_LEVEL_INFO)
740 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
741 __FILE__,__LINE__,cmd);
743 /* Verify the status of the device */
744 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
749 /* report count of read data available */
750 /* in next available frame (if any) */
751 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
752 buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
753 struct n_hdlc_buf, list_item);
758 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
759 error = put_user(count, (int __user *)arg);
763 /* get the pending tx byte count in the driver */
764 count = tty_chars_in_buffer(tty);
765 /* add size of next output frame in queue */
766 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
767 buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
768 struct n_hdlc_buf, list_item);
771 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
772 error = put_user(count, (int __user *)arg);
781 /* fall through to default */
784 error = n_tty_ioctl_helper(tty, file, cmd, arg);
789 } /* end of n_hdlc_tty_ioctl() */
792 * n_hdlc_tty_poll - TTY callback for poll system call
793 * @tty - pointer to tty instance data
794 * @filp - pointer to open file object for device
795 * @poll_table - wait queue for operations
797 * Determine which operations (read/write) will not block and return info
799 * Returns a bit mask containing info on which ops will not block.
801 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
804 struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
805 unsigned int mask = 0;
807 if (debuglevel >= DEBUG_LEVEL_INFO)
808 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
810 if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
811 /* queue current process into any wait queue that */
812 /* may awaken in the future (read and write) */
814 poll_wait(filp, &tty->read_wait, wait);
815 poll_wait(filp, &tty->write_wait, wait);
817 /* set bits for operations that won't block */
818 if (!list_empty(&n_hdlc->rx_buf_list.list))
819 mask |= POLLIN | POLLRDNORM; /* readable */
820 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
822 if (tty_hung_up_p(filp))
824 if (!tty_is_writelocked(tty) &&
825 !list_empty(&n_hdlc->tx_free_buf_list.list))
826 mask |= POLLOUT | POLLWRNORM; /* writable */
829 } /* end of n_hdlc_tty_poll() */
832 * n_hdlc_alloc - allocate an n_hdlc instance data structure
834 * Returns a pointer to newly created structure if success, otherwise %NULL
836 static struct n_hdlc *n_hdlc_alloc(void)
838 struct n_hdlc_buf *buf;
840 struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
845 memset(n_hdlc, 0, sizeof(*n_hdlc));
847 spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);
848 spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);
849 spin_lock_init(&n_hdlc->rx_buf_list.spinlock);
850 spin_lock_init(&n_hdlc->tx_buf_list.spinlock);
852 INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);
853 INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);
854 INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);
855 INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);
857 /* allocate free rx buffer list */
858 for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
859 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
861 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
862 else if (debuglevel >= DEBUG_LEVEL_INFO)
863 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
866 /* allocate free tx buffer list */
867 for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
868 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
870 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
871 else if (debuglevel >= DEBUG_LEVEL_INFO)
872 printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
875 /* Initialize the control block */
876 n_hdlc->magic = HDLC_MAGIC;
881 } /* end of n_hdlc_alloc() */
884 * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
885 * @buf_list - pointer to the buffer list
886 * @buf - pointer to the buffer
888 static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
889 struct n_hdlc_buf *buf)
893 spin_lock_irqsave(&buf_list->spinlock, flags);
895 list_add(&buf->list_item, &buf_list->list);
898 spin_unlock_irqrestore(&buf_list->spinlock, flags);
902 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
903 * @buf_list - pointer to buffer list
904 * @buf - pointer to buffer
906 static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
907 struct n_hdlc_buf *buf)
911 spin_lock_irqsave(&buf_list->spinlock, flags);
913 list_add_tail(&buf->list_item, &buf_list->list);
916 spin_unlock_irqrestore(&buf_list->spinlock, flags);
917 } /* end of n_hdlc_buf_put() */
920 * n_hdlc_buf_get - remove and return an HDLC buffer from list
921 * @buf_list - pointer to HDLC buffer list
923 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
925 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
927 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
930 struct n_hdlc_buf *buf;
932 spin_lock_irqsave(&buf_list->spinlock, flags);
934 buf = list_first_entry_or_null(&buf_list->list,
935 struct n_hdlc_buf, list_item);
937 list_del(&buf->list_item);
941 spin_unlock_irqrestore(&buf_list->spinlock, flags);
943 } /* end of n_hdlc_buf_get() */
945 static char hdlc_banner[] __initdata =
946 KERN_INFO "HDLC line discipline maxframe=%u\n";
947 static char hdlc_register_ok[] __initdata =
948 KERN_INFO "N_HDLC line discipline registered.\n";
949 static char hdlc_register_fail[] __initdata =
950 KERN_ERR "error registering line discipline: %d\n";
951 static char hdlc_init_fail[] __initdata =
952 KERN_INFO "N_HDLC: init failure %d\n";
954 static int __init n_hdlc_init(void)
958 /* range check maxframe arg */
961 else if (maxframe > 65535)
964 printk(hdlc_banner, maxframe);
966 status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
968 printk(hdlc_register_ok);
970 printk(hdlc_register_fail, status);
973 printk(hdlc_init_fail, status);
976 } /* end of init_module() */
978 static char hdlc_unregister_ok[] __exitdata =
979 KERN_INFO "N_HDLC: line discipline unregistered\n";
980 static char hdlc_unregister_fail[] __exitdata =
981 KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
983 static void __exit n_hdlc_exit(void)
985 /* Release tty registration of line discipline */
986 int status = tty_unregister_ldisc(N_HDLC);
989 printk(hdlc_unregister_fail, status);
991 printk(hdlc_unregister_ok);
994 module_init(n_hdlc_init);
995 module_exit(n_hdlc_exit);
997 MODULE_LICENSE("GPL");
998 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
999 module_param(debuglevel, int, 0);
1000 module_param(maxframe, int, 0);
1001 MODULE_ALIAS_LDISC(N_HDLC);