drivers/char/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  * $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  */
  80
  81 #define HDLC_MAGIC 0x239e
  82 #define HDLC_VERSION "$Revision: 4.8 $"
  83
  84 #include <linux/config.h>
  85 #include <linux/module.h>
  86 #include <linux/init.h>
  87 #include <linux/kernel.h>
  88 #include <linux/sched.h>
  89 #include <linux/types.h>
  90 #include <linux/fcntl.h>
  91 #include <linux/interrupt.h>
  92 #include <linux/ptrace.h>
  93
  94 #undef VERSION
  95 #define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
  96
  97 #include <linux/poll.h>
  98 #include <linux/in.h>
  99 #include <linux/ioctl.h>
 100 #include <linux/slab.h>
 101 #include <linux/tty.h>
 102 #include <linux/errno.h>
 103 #include <linux/string.h>       /* used in new tty drivers */
 104 #include <linux/signal.h>       /* used in new tty drivers */
 105 #include <linux/if.h>
 106 #include <linux/bitops.h>
 107
 108 #include <asm/system.h>
 109 #include <asm/termios.h>
 110 #include <asm/uaccess.h>
 111
 112 /*
 113  * Buffers for individual HDLC frames
 114  */
 115 #define MAX_HDLC_FRAME_SIZE 65535
 116 #define DEFAULT_RX_BUF_COUNT 10
 117 #define MAX_RX_BUF_COUNT 60
 118 #define DEFAULT_TX_BUF_COUNT 1
 119
 120 struct n_hdlc_buf {
 121         struct n_hdlc_buf *link;
 122         int               count;
 123         char              buf[1];
 124 };
 125
 126 #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
 127
 128 struct n_hdlc_buf_list {
 129         struct n_hdlc_buf *head;
 130         struct n_hdlc_buf *tail;
 131         int               count;
 132         spinlock_t        spinlock;
 133 };
 134
 135 /**
 136  * struct n_hdlc - per device instance data structure
 137  * @magic - magic value for structure
 138  * @flags - miscellaneous control flags
 139  * @tty - ptr to TTY structure
 140  * @backup_tty - TTY to use if tty gets closed
 141  * @tbusy - reentrancy flag for tx wakeup code
 142  * @woke_up - FIXME: describe this field
 143  * @tbuf - currently transmitting tx buffer
 144  * @tx_buf_list - list of pending transmit frame buffers
 145  * @rx_buf_list - list of received frame buffers
 146  * @tx_free_buf_list - list unused transmit frame buffers
 147  * @rx_free_buf_list - list unused received frame buffers
 148  */
 149 struct n_hdlc {
 150         int                     magic;
 151         __u32                   flags;
 152         struct tty_struct       *tty;
 153         struct tty_struct       *backup_tty;
 154         int                     tbusy;
 155         int                     woke_up;
 156         struct n_hdlc_buf       *tbuf;
 157         struct n_hdlc_buf_list  tx_buf_list;
 158         struct n_hdlc_buf_list  rx_buf_list;
 159         struct n_hdlc_buf_list  tx_free_buf_list;
 160         struct n_hdlc_buf_list  rx_free_buf_list;
 161 };
 162
 163 /*
 164  * HDLC buffer list manipulation functions
 165  */
 166 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list);
 167 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
 168                            struct n_hdlc_buf *buf);
 169 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
 170
 171 /* Local functions */
 172
 173 static struct n_hdlc *n_hdlc_alloc (void);
 174
 175 /* debug level can be set by insmod for debugging purposes */
 176 #define DEBUG_LEVEL_INFO        1
 177 static int debuglevel;
 178
 179 /* max frame size for memory allocations */
 180 static int maxframe = 4096;
 181
 182 /* TTY callbacks */
 183
 184 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 185                            __u8 __user *buf, size_t nr);
 186 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 187                             const unsigned char *buf, size_t nr);
 188 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 189                             unsigned int cmd, unsigned long arg);
 190 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
 191                                     poll_table *wait);
 192 static int n_hdlc_tty_open(struct tty_struct *tty);
 193 static void n_hdlc_tty_close(struct tty_struct *tty);
 194 static int n_hdlc_tty_room(struct tty_struct *tty);
 195 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
 196                                char *fp, int count);
 197 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
 198
 199 #define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
 200
 201 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
 202 #define n_hdlc2tty(n_hdlc)      ((n_hdlc)->tty)
 203
 204 static struct tty_ldisc n_hdlc_ldisc = {
 205         .owner          = THIS_MODULE,
 206         .magic          = TTY_LDISC_MAGIC,
 207         .name           = "hdlc",
 208         .open           = n_hdlc_tty_open,
 209         .close          = n_hdlc_tty_close,
 210         .read           = n_hdlc_tty_read,
 211         .write          = n_hdlc_tty_write,
 212         .ioctl          = n_hdlc_tty_ioctl,
 213         .poll           = n_hdlc_tty_poll,
 214         .receive_buf    = n_hdlc_tty_receive,
 215         .write_wakeup   = n_hdlc_tty_wakeup,
 216 };
 217
 218 /**
 219  * n_hdlc_release - release an n_hdlc per device line discipline info structure
 220  * @n_hdlc - per device line discipline info structure
 221  */
 222 static void n_hdlc_release(struct n_hdlc *n_hdlc)
 223 {
 224         struct tty_struct *tty = n_hdlc2tty (n_hdlc);
 225         struct n_hdlc_buf *buf;
 226
 227         if (debuglevel >= DEBUG_LEVEL_INFO)
 228                 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
 229
 230         /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
 231         wake_up_interruptible (&tty->read_wait);
 232         wake_up_interruptible (&tty->write_wait);
 233
 234         if (tty != NULL && tty->disc_data == n_hdlc)
 235                 tty->disc_data = NULL;  /* Break the tty->n_hdlc link */
 236
 237         /* Release transmit and receive buffers */
 238         for(;;) {
 239                 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
 240                 if (buf) {
 241                         kfree(buf);
 242                 } else
 243                         break;
 244         }
 245         for(;;) {
 246                 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
 247                 if (buf) {
 248                         kfree(buf);
 249                 } else
 250                         break;
 251         }
 252         for(;;) {
 253                 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
 254                 if (buf) {
 255                         kfree(buf);
 256                 } else
 257                         break;
 258         }
 259         for(;;) {
 260                 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 261                 if (buf) {
 262                         kfree(buf);
 263                 } else
 264                         break;
 265         }
 266         kfree(n_hdlc->tbuf);
 267         kfree(n_hdlc);
 268
 269 }       /* end of n_hdlc_release() */
 270
 271 /**
 272  * n_hdlc_tty_close - line discipline close
 273  * @tty - pointer to tty info structure
 274  *
 275  * Called when the line discipline is changed to something
 276  * else, the tty is closed, or the tty detects a hangup.
 277  */
 278 static void n_hdlc_tty_close(struct tty_struct *tty)
 279 {
 280         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 281
 282         if (debuglevel >= DEBUG_LEVEL_INFO)
 283                 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
 284
 285         if (n_hdlc != NULL) {
 286                 if (n_hdlc->magic != HDLC_MAGIC) {
 287                         printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
 288                         return;
 289                 }
 290 #if defined(TTY_NO_WRITE_SPLIT)
 291                 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
 292 #endif
 293                 tty->disc_data = NULL;
 294                 if (tty == n_hdlc->backup_tty)
 295                         n_hdlc->backup_tty = NULL;
 296                 if (tty != n_hdlc->tty)
 297                         return;
 298                 if (n_hdlc->backup_tty) {
 299                         n_hdlc->tty = n_hdlc->backup_tty;
 300                 } else {
 301                         n_hdlc_release (n_hdlc);
 302                 }
 303         }
 304
 305         if (debuglevel >= DEBUG_LEVEL_INFO)
 306                 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
 307
 308 }       /* end of n_hdlc_tty_close() */
 309
 310 /**
 311  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
 312  * @tty - pointer to tty info structure
 313  *
 314  * Returns 0 if success, otherwise error code
 315  */
 316 static int n_hdlc_tty_open (struct tty_struct *tty)
 317 {
 318         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 319
 320         if (debuglevel >= DEBUG_LEVEL_INFO)
 321                 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
 322                 __FILE__,__LINE__,
 323                 tty->name);
 324
 325         /* There should not be an existing table for this slot. */
 326         if (n_hdlc) {
 327                 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
 328                 return -EEXIST;
 329         }
 330
 331         n_hdlc = n_hdlc_alloc();
 332         if (!n_hdlc) {
 333                 printk (KERN_ERR "n_hdlc_alloc failed\n");
 334                 return -ENFILE;
 335         }
 336
 337         tty->disc_data = n_hdlc;
 338         n_hdlc->tty    = tty;
 339         tty->receive_room = 65536;
 340
 341 #if defined(TTY_NO_WRITE_SPLIT)
 342         /* change tty_io write() to not split large writes into 8K chunks */
 343         set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
 344 #endif
 345
 346         /* Flush any pending characters in the driver and discipline. */
 347
 348         if (tty->ldisc.flush_buffer)
 349                 tty->ldisc.flush_buffer (tty);
 350
 351         if (tty->driver->flush_buffer)
 352                 tty->driver->flush_buffer (tty);
 353
 354         if (debuglevel >= DEBUG_LEVEL_INFO)
 355                 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
 356
 357         return 0;
 358
 359 }       /* end of n_tty_hdlc_open() */
 360
 361 /**
 362  * n_hdlc_send_frames - send frames on pending send buffer list
 363  * @n_hdlc - pointer to ldisc instance data
 364  * @tty - pointer to tty instance data
 365  *
 366  * Send frames on pending send buffer list until the driver does not accept a
 367  * frame (busy) this function is called after adding a frame to the send buffer
 368  * list and by the tty wakeup callback.
 369  */
 370 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
 371 {
 372         register int actual;
 373         unsigned long flags;
 374         struct n_hdlc_buf *tbuf;
 375
 376         if (debuglevel >= DEBUG_LEVEL_INFO)
 377                 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
 378  check_again:
 379
 380         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 381         if (n_hdlc->tbusy) {
 382                 n_hdlc->woke_up = 1;
 383                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 384                 return;
 385         }
 386         n_hdlc->tbusy = 1;
 387         n_hdlc->woke_up = 0;
 388         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 389
 390         /* get current transmit buffer or get new transmit */
 391         /* buffer from list of pending transmit buffers */
 392
 393         tbuf = n_hdlc->tbuf;
 394         if (!tbuf)
 395                 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 396
 397         while (tbuf) {
 398                 if (debuglevel >= DEBUG_LEVEL_INFO)
 399                         printk("%s(%d)sending frame %p, count=%d\n",
 400                                 __FILE__,__LINE__,tbuf,tbuf->count);
 401
 402                 /* Send the next block of data to device */
 403                 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
 404                 actual = tty->driver->write(tty, tbuf->buf, tbuf->count);
 405
 406                 /* if transmit error, throw frame away by */
 407                 /* pretending it was accepted by driver */
 408                 if (actual < 0)
 409                         actual = tbuf->count;
 410
 411                 if (actual == tbuf->count) {
 412                         if (debuglevel >= DEBUG_LEVEL_INFO)
 413                                 printk("%s(%d)frame %p completed\n",
 414                                         __FILE__,__LINE__,tbuf);
 415
 416                         /* free current transmit buffer */
 417                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
 418
 419                         /* this tx buffer is done */
 420                         n_hdlc->tbuf = NULL;
 421
 422                         /* wait up sleeping writers */
 423                         wake_up_interruptible(&tty->write_wait);
 424
 425                         /* get next pending transmit buffer */
 426                         tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 427                 } else {
 428                         if (debuglevel >= DEBUG_LEVEL_INFO)
 429                                 printk("%s(%d)frame %p pending\n",
 430                                         __FILE__,__LINE__,tbuf);
 431
 432                         /* buffer not accepted by driver */
 433                         /* set this buffer as pending buffer */
 434                         n_hdlc->tbuf = tbuf;
 435                         break;
 436                 }
 437         }
 438
 439         if (!tbuf)
 440                 tty->flags  &= ~(1 << TTY_DO_WRITE_WAKEUP);
 441
 442         /* Clear the re-entry flag */
 443         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 444         n_hdlc->tbusy = 0;
 445         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 446
 447         if (n_hdlc->woke_up)
 448           goto check_again;
 449
 450         if (debuglevel >= DEBUG_LEVEL_INFO)
 451                 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
 452
 453 }       /* end of n_hdlc_send_frames() */
 454
 455 /**
 456  * n_hdlc_tty_wakeup - Callback for transmit wakeup
 457  * @tty - pointer to associated tty instance data
 458  *
 459  * Called when low level device driver can accept more send data.
 460  */
 461 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
 462 {
 463         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 464
 465         if (debuglevel >= DEBUG_LEVEL_INFO)
 466                 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
 467
 468         if (!n_hdlc)
 469                 return;
 470
 471         if (tty != n_hdlc->tty) {
 472                 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
 473                 return;
 474         }
 475
 476         n_hdlc_send_frames (n_hdlc, tty);
 477
 478 }       /* end of n_hdlc_tty_wakeup() */
 479
 480 /**
 481  * n_hdlc_tty_receive - Called by tty driver when receive data is available
 482  * @tty - pointer to tty instance data
 483  * @data - pointer to received data
 484  * @flags - pointer to flags for data
 485  * @count - count of received data in bytes
 486  *
 487  * Called by tty low level driver when receive data is available. Data is
 488  * interpreted as one HDLC frame.
 489  */
 490 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
 491                                char *flags, int count)
 492 {
 493         register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 494         register struct n_hdlc_buf *buf;
 495
 496         if (debuglevel >= DEBUG_LEVEL_INFO)
 497                 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
 498                         __FILE__,__LINE__, count);
 499
 500         /* This can happen if stuff comes in on the backup tty */
 501         if (n_hdlc == 0 || tty != n_hdlc->tty)
 502                 return;
 503
 504         /* verify line is using HDLC discipline */
 505         if (n_hdlc->magic != HDLC_MAGIC) {
 506                 printk("%s(%d) line not using HDLC discipline\n",
 507                         __FILE__,__LINE__);
 508                 return;
 509         }
 510
 511         if ( count>maxframe ) {
 512                 if (debuglevel >= DEBUG_LEVEL_INFO)
 513                         printk("%s(%d) rx count>maxframesize, data discarded\n",
 514                                __FILE__,__LINE__);
 515                 return;
 516         }
 517
 518         /* get a free HDLC buffer */
 519         buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
 520         if (!buf) {
 521                 /* no buffers in free list, attempt to allocate another rx buffer */
 522                 /* unless the maximum count has been reached */
 523                 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
 524                         buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
 525         }
 526
 527         if (!buf) {
 528                 if (debuglevel >= DEBUG_LEVEL_INFO)
 529                         printk("%s(%d) no more rx buffers, data discarded\n",
 530                                __FILE__,__LINE__);
 531                 return;
 532         }
 533
 534         /* copy received data to HDLC buffer */
 535         memcpy(buf->buf,data,count);
 536         buf->count=count;
 537
 538         /* add HDLC buffer to list of received frames */
 539         n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
 540
 541         /* wake up any blocked reads and perform async signalling */
 542         wake_up_interruptible (&tty->read_wait);
 543         if (n_hdlc->tty->fasync != NULL)
 544                 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
 545
 546 }       /* end of n_hdlc_tty_receive() */
 547
 548 /**
 549  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
 550  * @tty - pointer to tty instance data
 551  * @file - pointer to open file object
 552  * @buf - pointer to returned data buffer
 553  * @nr - size of returned data buffer
 554  *
 555  * Returns the number of bytes returned or error code.
 556  */
 557 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 558                            __u8 __user *buf, size_t nr)
 559 {
 560         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 561         int ret;
 562         struct n_hdlc_buf *rbuf;
 563
 564         if (debuglevel >= DEBUG_LEVEL_INFO)
 565                 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
 566
 567         /* Validate the pointers */
 568         if (!n_hdlc)
 569                 return -EIO;
 570
 571         /* verify user access to buffer */
 572         if (!access_ok(VERIFY_WRITE, buf, nr)) {
 573                 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
 574                 "buffer\n", __FILE__, __LINE__);
 575                 return -EFAULT;
 576         }
 577
 578         for (;;) {
 579                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 580                         return -EIO;
 581
 582                 n_hdlc = tty2n_hdlc (tty);
 583                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
 584                          tty != n_hdlc->tty)
 585                         return 0;
 586
 587                 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
 588                 if (rbuf)
 589                         break;
 590
 591                 /* no data */
 592                 if (file->f_flags & O_NONBLOCK)
 593                         return -EAGAIN;
 594
 595                 interruptible_sleep_on (&tty->read_wait);
 596                 if (signal_pending(current))
 597                         return -EINTR;
 598         }
 599
 600         if (rbuf->count > nr)
 601                 /* frame too large for caller's buffer (discard frame) */
 602                 ret = -EOVERFLOW;
 603         else {
 604                 /* Copy the data to the caller's buffer */
 605                 if (copy_to_user(buf, rbuf->buf, rbuf->count))
 606                         ret = -EFAULT;
 607                 else
 608                         ret = rbuf->count;
 609         }
 610
 611         /* return HDLC buffer to free list unless the free list */
 612         /* count has exceeded the default value, in which case the */
 613         /* buffer is freed back to the OS to conserve memory */
 614         if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
 615                 kfree(rbuf);
 616         else
 617                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
 618
 619         return ret;
 620
 621 }       /* end of n_hdlc_tty_read() */
 622
 623 /**
 624  * n_hdlc_tty_write - write a single frame of data to device
 625  * @tty - pointer to associated tty device instance data
 626  * @file - pointer to file object data
 627  * @data - pointer to transmit data (one frame)
 628  * @count - size of transmit frame in bytes
 629  *
 630  * Returns the number of bytes written (or error code).
 631  */
 632 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 633                             const unsigned char *data, size_t count)
 634 {
 635         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 636         int error = 0;
 637         DECLARE_WAITQUEUE(wait, current);
 638         struct n_hdlc_buf *tbuf;
 639
 640         if (debuglevel >= DEBUG_LEVEL_INFO)
 641                 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
 642                         __FILE__,__LINE__,count);
 643
 644         /* Verify pointers */
 645         if (!n_hdlc)
 646                 return -EIO;
 647
 648         if (n_hdlc->magic != HDLC_MAGIC)
 649                 return -EIO;
 650
 651         /* verify frame size */
 652         if (count > maxframe ) {
 653                 if (debuglevel & DEBUG_LEVEL_INFO)
 654                         printk (KERN_WARNING
 655                                 "n_hdlc_tty_write: truncating user packet "
 656                                 "from %lu to %d\n", (unsigned long) count,
 657                                 maxframe );
 658                 count = maxframe;
 659         }
 660
 661         add_wait_queue(&tty->write_wait, &wait);
 662         set_current_state(TASK_INTERRUPTIBLE);
 663
 664         /* Allocate transmit buffer */
 665         /* sleep until transmit buffer available */
 666         while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
 667                 schedule();
 668
 669                 n_hdlc = tty2n_hdlc (tty);
 670                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
 671                     tty != n_hdlc->tty) {
 672                         printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
 673                         error = -EIO;
 674                         break;
 675                 }
 676
 677                 if (signal_pending(current)) {
 678                         error = -EINTR;
 679                         break;
 680                 }
 681         }
 682
 683         set_current_state(TASK_RUNNING);
 684         remove_wait_queue(&tty->write_wait, &wait);
 685
 686         if (!error) {
 687                 /* Retrieve the user's buffer */
 688                 memcpy(tbuf->buf, data, count);
 689
 690                 /* Send the data */
 691                 tbuf->count = error = count;
 692                 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
 693                 n_hdlc_send_frames(n_hdlc,tty);
 694         }
 695
 696         return error;
 697
 698 }       /* end of n_hdlc_tty_write() */
 699
 700 /**
 701  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
 702  * @tty - pointer to tty instance data
 703  * @file - pointer to open file object for device
 704  * @cmd - IOCTL command code
 705  * @arg - argument for IOCTL call (cmd dependent)
 706  *
 707  * Returns command dependent result.
 708  */
 709 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 710                             unsigned int cmd, unsigned long arg)
 711 {
 712         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 713         int error = 0;
 714         int count;
 715         unsigned long flags;
 716
 717         if (debuglevel >= DEBUG_LEVEL_INFO)
 718                 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
 719                         __FILE__,__LINE__,cmd);
 720
 721         /* Verify the status of the device */
 722         if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
 723                 return -EBADF;
 724
 725         switch (cmd) {
 726         case FIONREAD:
 727                 /* report count of read data available */
 728                 /* in next available frame (if any) */
 729                 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
 730                 if (n_hdlc->rx_buf_list.head)
 731                         count = n_hdlc->rx_buf_list.head->count;
 732                 else
 733                         count = 0;
 734                 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
 735                 error = put_user(count, (int __user *)arg);
 736                 break;
 737
 738         case TIOCOUTQ:
 739                 /* get the pending tx byte count in the driver */
 740                 count = tty->driver->chars_in_buffer ?
 741                                 tty->driver->chars_in_buffer(tty) : 0;
 742                 /* add size of next output frame in queue */
 743                 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
 744                 if (n_hdlc->tx_buf_list.head)
 745                         count += n_hdlc->tx_buf_list.head->count;
 746                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
 747                 error = put_user(count, (int __user *)arg);
 748                 break;
 749
 750         default:
 751                 error = n_tty_ioctl (tty, file, cmd, arg);
 752                 break;
 753         }
 754         return error;
 755
 756 }       /* end of n_hdlc_tty_ioctl() */
 757
 758 /**
 759  * n_hdlc_tty_poll - TTY callback for poll system call
 760  * @tty - pointer to tty instance data
 761  * @filp - pointer to open file object for device
 762  * @poll_table - wait queue for operations
 763  *
 764  * Determine which operations (read/write) will not block and return info
 765  * to caller.
 766  * Returns a bit mask containing info on which ops will not block.
 767  */
 768 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
 769                                     poll_table *wait)
 770 {
 771         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 772         unsigned int mask = 0;
 773
 774         if (debuglevel >= DEBUG_LEVEL_INFO)
 775                 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
 776
 777         if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
 778                 /* queue current process into any wait queue that */
 779                 /* may awaken in the future (read and write) */
 780
 781                 poll_wait(filp, &tty->read_wait, wait);
 782                 poll_wait(filp, &tty->write_wait, wait);
 783
 784                 /* set bits for operations that won't block */
 785                 if(n_hdlc->rx_buf_list.head)
 786                         mask |= POLLIN | POLLRDNORM;    /* readable */
 787                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 788                         mask |= POLLHUP;
 789                 if(tty_hung_up_p(filp))
 790                         mask |= POLLHUP;
 791                 if(n_hdlc->tx_free_buf_list.head)
 792                         mask |= POLLOUT | POLLWRNORM;   /* writable */
 793         }
 794         return mask;
 795 }       /* end of n_hdlc_tty_poll() */
 796
 797 /**
 798  * n_hdlc_alloc - allocate an n_hdlc instance data structure
 799  *
 800  * Returns a pointer to newly created structure if success, otherwise %NULL
 801  */
 802 static struct n_hdlc *n_hdlc_alloc(void)
 803 {
 804         struct n_hdlc_buf *buf;
 805         int i;
 806         struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
 807
 808         if (!n_hdlc)
 809                 return NULL;
 810
 811         memset(n_hdlc, 0, sizeof(*n_hdlc));
 812
 813         n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
 814         n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
 815         n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
 816         n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
 817
 818         /* allocate free rx buffer list */
 819         for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
 820                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
 821                 if (buf)
 822                         n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
 823                 else if (debuglevel >= DEBUG_LEVEL_INFO)
 824                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
 825         }
 826
 827         /* allocate free tx buffer list */
 828         for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
 829                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
 830                 if (buf)
 831                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
 832                 else if (debuglevel >= DEBUG_LEVEL_INFO)
 833                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
 834         }
 835
 836         /* Initialize the control block */
 837         n_hdlc->magic  = HDLC_MAGIC;
 838         n_hdlc->flags  = 0;
 839
 840         return n_hdlc;
 841
 842 }       /* end of n_hdlc_alloc() */
 843
 844 /**
 845  * n_hdlc_buf_list_init - initialize specified HDLC buffer list
 846  * @list - pointer to buffer list
 847  */
 848 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
 849 {
 850         memset(list, 0, sizeof(*list));
 851         spin_lock_init(&list->spinlock);
 852 }       /* end of n_hdlc_buf_list_init() */
 853
 854 /**
 855  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
 856  * @list - pointer to buffer list
 857  * @buf - pointer to buffer
 858  */
 859 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
 860                            struct n_hdlc_buf *buf)
 861 {
 862         unsigned long flags;
 863         spin_lock_irqsave(&list->spinlock,flags);
 864
 865         buf->link=NULL;
 866         if(list->tail)
 867                 list->tail->link = buf;
 868         else
 869                 list->head = buf;
 870         list->tail = buf;
 871         (list->count)++;
 872
 873         spin_unlock_irqrestore(&list->spinlock,flags);
 874
 875 }       /* end of n_hdlc_buf_put() */
 876
 877 /**
 878  * n_hdlc_buf_get - remove and return an HDLC buffer from list
 879  * @list - pointer to HDLC buffer list
 880  *
 881  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
 882  * list.
 883  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
 884  */
 885 static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
 886 {
 887         unsigned long flags;
 888         struct n_hdlc_buf *buf;
 889         spin_lock_irqsave(&list->spinlock,flags);
 890
 891         buf = list->head;
 892         if (buf) {
 893                 list->head = buf->link;
 894                 (list->count)--;
 895         }
 896         if (!list->head)
 897                 list->tail = NULL;
 898
 899         spin_unlock_irqrestore(&list->spinlock,flags);
 900         return buf;
 901
 902 }       /* end of n_hdlc_buf_get() */
 903
 904 static char hdlc_banner[] __initdata =
 905         KERN_INFO "HDLC line discipline: version " HDLC_VERSION
 906         ", maxframe=%u\n";
 907 static char hdlc_register_ok[] __initdata =
 908         KERN_INFO "N_HDLC line discipline registered.\n";
 909 static char hdlc_register_fail[] __initdata =
 910         KERN_ERR "error registering line discipline: %d\n";
 911 static char hdlc_init_fail[] __initdata =
 912         KERN_INFO "N_HDLC: init failure %d\n";
 913
 914 static int __init n_hdlc_init(void)
 915 {
 916         int status;
 917
 918         /* range check maxframe arg */
 919         if (maxframe < 4096)
 920                 maxframe = 4096;
 921         else if (maxframe > 65535)
 922                 maxframe = 65535;
 923
 924         printk(hdlc_banner, maxframe);
 925
 926         status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
 927         if (!status)
 928                 printk(hdlc_register_ok);
 929         else
 930                 printk(hdlc_register_fail, status);
 931
 932         if (status)
 933                 printk(hdlc_init_fail, status);
 934         return status;
 935
 936 }       /* end of init_module() */
 937
 938 static char hdlc_unregister_ok[] __exitdata =
 939         KERN_INFO "N_HDLC: line discipline unregistered\n";
 940 static char hdlc_unregister_fail[] __exitdata =
 941         KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
 942
 943 static void __exit n_hdlc_exit(void)
 944 {
 945         /* Release tty registration of line discipline */
 946         int status = tty_unregister_ldisc(N_HDLC);
 947
 948         if (status)
 949                 printk(hdlc_unregister_fail, status);
 950         else
 951                 printk(hdlc_unregister_ok);
 952 }
 953
 954 module_init(n_hdlc_init);
 955 module_exit(n_hdlc_exit);
 956
 957 MODULE_LICENSE("GPL");
 958 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
 959 module_param(debuglevel, int, 0);
 960 module_param(maxframe, int, 0);
 961 MODULE_ALIAS_LDISC(N_HDLC);