drivers/tty/n_hdlc.c

   1 /* generic HDLC line discipline for Linux
   2  *
   3  * Written by Paul Fulghum paulkf@microgate.com
   4  * for Microgate Corporation
   5  *
   6  * Microgate and SyncLink are registered trademarks of Microgate Corporation
   7  *
   8  * Adapted from ppp.c, written by Michael Callahan <callahan@maths.ox.ac.uk>,
   9  *      Al Longyear <longyear@netcom.com>,
  10  *      Paul Mackerras <Paul.Mackerras@cs.anu.edu.au>
  11  *
  12  * Original release 01/11/99
  13  *
  14  * This code is released under the GNU General Public License (GPL)
  15  *
  16  * This module implements the tty line discipline N_HDLC for use with
  17  * tty device drivers that support bit-synchronous HDLC communications.
  18  *
  19  * All HDLC data is frame oriented which means:
  20  *
  21  * 1. tty write calls represent one complete transmit frame of data
  22  *    The device driver should accept the complete frame or none of
  23  *    the frame (busy) in the write method. Each write call should have
  24  *    a byte count in the range of 2-65535 bytes (2 is min HDLC frame
  25  *    with 1 addr byte and 1 ctrl byte). The max byte count of 65535
  26  *    should include any crc bytes required. For example, when using
  27  *    CCITT CRC32, 4 crc bytes are required, so the maximum size frame
  28  *    the application may transmit is limited to 65531 bytes. For CCITT
  29  *    CRC16, the maximum application frame size would be 65533.
  30  *
  31  *
  32  * 2. receive callbacks from the device driver represents
  33  *    one received frame. The device driver should bypass
  34  *    the tty flip buffer and call the line discipline receive
  35  *    callback directly to avoid fragmenting or concatenating
  36  *    multiple frames into a single receive callback.
  37  *
  38  *    The HDLC line discipline queues the receive frames in separate
  39  *    buffers so complete receive frames can be returned by the
  40  *    tty read calls.
  41  *
  42  * 3. tty read calls returns an entire frame of data or nothing.
  43  *
  44  * 4. all send and receive data is considered raw. No processing
  45  *    or translation is performed by the line discipline, regardless
  46  *    of the tty flags
  47  *
  48  * 5. When line discipline is queried for the amount of receive
  49  *    data available (FIOC), 0 is returned if no data available,
  50  *    otherwise the count of the next available frame is returned.
  51  *    (instead of the sum of all received frame counts).
  52  *
  53  * These conventions allow the standard tty programming interface
  54  * to be used for synchronous HDLC applications when used with
  55  * this line discipline (or another line discipline that is frame
  56  * oriented such as N_PPP).
  57  *
  58  * The SyncLink driver (synclink.c) implements both asynchronous
  59  * (using standard line discipline N_TTY) and synchronous HDLC
  60  * (using N_HDLC) communications, with the latter using the above
  61  * conventions.
  62  *
  63  * This implementation is very basic and does not maintain
  64  * any statistics. The main point is to enforce the raw data
  65  * and frame orientation of HDLC communications.
  66  *
  67  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  68  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  69  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  70  * DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
  71  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  72  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  73  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  74  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  75  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  76  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  77  * OF THE POSSIBILITY OF SUCH DAMAGE.
  78  */
  79
  80 #define HDLC_MAGIC 0x239e
  81
  82 #include <linux/module.h>
  83 #include <linux/init.h>
  84 #include <linux/kernel.h>
  85 #include <linux/sched.h>
  86 #include <linux/types.h>
  87 #include <linux/fcntl.h>
  88 #include <linux/interrupt.h>
  89 #include <linux/ptrace.h>
  90
  91 #undef VERSION
  92 #define VERSION(major,minor,patch) (((((major)<<8)+(minor))<<8)+(patch))
  93
  94 #include <linux/poll.h>
  95 #include <linux/in.h>
  96 #include <linux/ioctl.h>
  97 #include <linux/slab.h>
  98 #include <linux/tty.h>
  99 #include <linux/errno.h>
 100 #include <linux/smp_lock.h>
 101 #include <linux/string.h>       /* used in new tty drivers */
 102 #include <linux/signal.h>       /* used in new tty drivers */
 103 #include <linux/if.h>
 104 #include <linux/bitops.h>
 105
 106 #include <asm/system.h>
 107 #include <asm/termios.h>
 108 #include <asm/uaccess.h>
 109
 110 /*
 111  * Buffers for individual HDLC frames
 112  */
 113 #define MAX_HDLC_FRAME_SIZE 65535
 114 #define DEFAULT_RX_BUF_COUNT 10
 115 #define MAX_RX_BUF_COUNT 60
 116 #define DEFAULT_TX_BUF_COUNT 3
 117
 118 struct n_hdlc_buf {
 119         struct n_hdlc_buf *link;
 120         int               count;
 121         char              buf[1];
 122 };
 123
 124 #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
 125
 126 struct n_hdlc_buf_list {
 127         struct n_hdlc_buf *head;
 128         struct n_hdlc_buf *tail;
 129         int               count;
 130         spinlock_t        spinlock;
 131 };
 132
 133 /**
 134  * struct n_hdlc - per device instance data structure
 135  * @magic - magic value for structure
 136  * @flags - miscellaneous control flags
 137  * @tty - ptr to TTY structure
 138  * @backup_tty - TTY to use if tty gets closed
 139  * @tbusy - reentrancy flag for tx wakeup code
 140  * @woke_up - FIXME: describe this field
 141  * @tbuf - currently transmitting tx buffer
 142  * @tx_buf_list - list of pending transmit frame buffers
 143  * @rx_buf_list - list of received frame buffers
 144  * @tx_free_buf_list - list unused transmit frame buffers
 145  * @rx_free_buf_list - list unused received frame buffers
 146  */
 147 struct n_hdlc {
 148         int                     magic;
 149         __u32                   flags;
 150         struct tty_struct       *tty;
 151         struct tty_struct       *backup_tty;
 152         int                     tbusy;
 153         int                     woke_up;
 154         struct n_hdlc_buf       *tbuf;
 155         struct n_hdlc_buf_list  tx_buf_list;
 156         struct n_hdlc_buf_list  rx_buf_list;
 157         struct n_hdlc_buf_list  tx_free_buf_list;
 158         struct n_hdlc_buf_list  rx_free_buf_list;
 159 };
 160
 161 /*
 162  * HDLC buffer list manipulation functions
 163  */
 164 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list);
 165 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
 166                            struct n_hdlc_buf *buf);
 167 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
 168
 169 /* Local functions */
 170
 171 static struct n_hdlc *n_hdlc_alloc (void);
 172
 173 /* debug level can be set by insmod for debugging purposes */
 174 #define DEBUG_LEVEL_INFO        1
 175 static int debuglevel;
 176
 177 /* max frame size for memory allocations */
 178 static int maxframe = 4096;
 179
 180 /* TTY callbacks */
 181
 182 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 183                            __u8 __user *buf, size_t nr);
 184 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 185                             const unsigned char *buf, size_t nr);
 186 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 187                             unsigned int cmd, unsigned long arg);
 188 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
 189                                     poll_table *wait);
 190 static int n_hdlc_tty_open(struct tty_struct *tty);
 191 static void n_hdlc_tty_close(struct tty_struct *tty);
 192 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
 193                                char *fp, int count);
 194 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
 195
 196 #define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
 197
 198 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
 199 #define n_hdlc2tty(n_hdlc)      ((n_hdlc)->tty)
 200
 201 static void flush_rx_queue(struct tty_struct *tty)
 202 {
 203         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 204         struct n_hdlc_buf *buf;
 205
 206         while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
 207                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
 208 }
 209
 210 static void flush_tx_queue(struct tty_struct *tty)
 211 {
 212         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 213         struct n_hdlc_buf *buf;
 214         unsigned long flags;
 215
 216         while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
 217                 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
 218         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 219         if (n_hdlc->tbuf) {
 220                 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, n_hdlc->tbuf);
 221                 n_hdlc->tbuf = NULL;
 222         }
 223         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 224 }
 225
 226 static struct tty_ldisc_ops n_hdlc_ldisc = {
 227         .owner          = THIS_MODULE,
 228         .magic          = TTY_LDISC_MAGIC,
 229         .name           = "hdlc",
 230         .open           = n_hdlc_tty_open,
 231         .close          = n_hdlc_tty_close,
 232         .read           = n_hdlc_tty_read,
 233         .write          = n_hdlc_tty_write,
 234         .ioctl          = n_hdlc_tty_ioctl,
 235         .poll           = n_hdlc_tty_poll,
 236         .receive_buf    = n_hdlc_tty_receive,
 237         .write_wakeup   = n_hdlc_tty_wakeup,
 238         .flush_buffer   = flush_rx_queue,
 239 };
 240
 241 /**
 242  * n_hdlc_release - release an n_hdlc per device line discipline info structure
 243  * @n_hdlc - per device line discipline info structure
 244  */
 245 static void n_hdlc_release(struct n_hdlc *n_hdlc)
 246 {
 247         struct tty_struct *tty = n_hdlc2tty (n_hdlc);
 248         struct n_hdlc_buf *buf;
 249
 250         if (debuglevel >= DEBUG_LEVEL_INFO)
 251                 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
 252
 253         /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
 254         wake_up_interruptible (&tty->read_wait);
 255         wake_up_interruptible (&tty->write_wait);
 256
 257         if (tty->disc_data == n_hdlc)
 258                 tty->disc_data = NULL;  /* Break the tty->n_hdlc link */
 259
 260         /* Release transmit and receive buffers */
 261         for(;;) {
 262                 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
 263                 if (buf) {
 264                         kfree(buf);
 265                 } else
 266                         break;
 267         }
 268         for(;;) {
 269                 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
 270                 if (buf) {
 271                         kfree(buf);
 272                 } else
 273                         break;
 274         }
 275         for(;;) {
 276                 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
 277                 if (buf) {
 278                         kfree(buf);
 279                 } else
 280                         break;
 281         }
 282         for(;;) {
 283                 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 284                 if (buf) {
 285                         kfree(buf);
 286                 } else
 287                         break;
 288         }
 289         kfree(n_hdlc->tbuf);
 290         kfree(n_hdlc);
 291
 292 }       /* end of n_hdlc_release() */
 293
 294 /**
 295  * n_hdlc_tty_close - line discipline close
 296  * @tty - pointer to tty info structure
 297  *
 298  * Called when the line discipline is changed to something
 299  * else, the tty is closed, or the tty detects a hangup.
 300  */
 301 static void n_hdlc_tty_close(struct tty_struct *tty)
 302 {
 303         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 304
 305         if (debuglevel >= DEBUG_LEVEL_INFO)
 306                 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
 307
 308         if (n_hdlc != NULL) {
 309                 if (n_hdlc->magic != HDLC_MAGIC) {
 310                         printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
 311                         return;
 312                 }
 313 #if defined(TTY_NO_WRITE_SPLIT)
 314                 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
 315 #endif
 316                 tty->disc_data = NULL;
 317                 if (tty == n_hdlc->backup_tty)
 318                         n_hdlc->backup_tty = NULL;
 319                 if (tty != n_hdlc->tty)
 320                         return;
 321                 if (n_hdlc->backup_tty) {
 322                         n_hdlc->tty = n_hdlc->backup_tty;
 323                 } else {
 324                         n_hdlc_release (n_hdlc);
 325                 }
 326         }
 327
 328         if (debuglevel >= DEBUG_LEVEL_INFO)
 329                 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
 330
 331 }       /* end of n_hdlc_tty_close() */
 332
 333 /**
 334  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
 335  * @tty - pointer to tty info structure
 336  *
 337  * Returns 0 if success, otherwise error code
 338  */
 339 static int n_hdlc_tty_open (struct tty_struct *tty)
 340 {
 341         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 342
 343         if (debuglevel >= DEBUG_LEVEL_INFO)
 344                 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
 345                 __FILE__,__LINE__,
 346                 tty->name);
 347
 348         /* There should not be an existing table for this slot. */
 349         if (n_hdlc) {
 350                 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
 351                 return -EEXIST;
 352         }
 353
 354         n_hdlc = n_hdlc_alloc();
 355         if (!n_hdlc) {
 356                 printk (KERN_ERR "n_hdlc_alloc failed\n");
 357                 return -ENFILE;
 358         }
 359
 360         tty->disc_data = n_hdlc;
 361         n_hdlc->tty    = tty;
 362         tty->receive_room = 65536;
 363
 364 #if defined(TTY_NO_WRITE_SPLIT)
 365         /* change tty_io write() to not split large writes into 8K chunks */
 366         set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
 367 #endif
 368
 369         /* flush receive data from driver */
 370         tty_driver_flush_buffer(tty);
 371
 372         if (debuglevel >= DEBUG_LEVEL_INFO)
 373                 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
 374
 375         return 0;
 376
 377 }       /* end of n_tty_hdlc_open() */
 378
 379 /**
 380  * n_hdlc_send_frames - send frames on pending send buffer list
 381  * @n_hdlc - pointer to ldisc instance data
 382  * @tty - pointer to tty instance data
 383  *
 384  * Send frames on pending send buffer list until the driver does not accept a
 385  * frame (busy) this function is called after adding a frame to the send buffer
 386  * list and by the tty wakeup callback.
 387  */
 388 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
 389 {
 390         register int actual;
 391         unsigned long flags;
 392         struct n_hdlc_buf *tbuf;
 393
 394         if (debuglevel >= DEBUG_LEVEL_INFO)
 395                 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
 396  check_again:
 397
 398         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 399         if (n_hdlc->tbusy) {
 400                 n_hdlc->woke_up = 1;
 401                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 402                 return;
 403         }
 404         n_hdlc->tbusy = 1;
 405         n_hdlc->woke_up = 0;
 406         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 407
 408         /* get current transmit buffer or get new transmit */
 409         /* buffer from list of pending transmit buffers */
 410
 411         tbuf = n_hdlc->tbuf;
 412         if (!tbuf)
 413                 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 414
 415         while (tbuf) {
 416                 if (debuglevel >= DEBUG_LEVEL_INFO)
 417                         printk("%s(%d)sending frame %p, count=%d\n",
 418                                 __FILE__,__LINE__,tbuf,tbuf->count);
 419
 420                 /* Send the next block of data to device */
 421                 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
 422                 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
 423
 424                 /* rollback was possible and has been done */
 425                 if (actual == -ERESTARTSYS) {
 426                         n_hdlc->tbuf = tbuf;
 427                         break;
 428                 }
 429                 /* if transmit error, throw frame away by */
 430                 /* pretending it was accepted by driver */
 431                 if (actual < 0)
 432                         actual = tbuf->count;
 433
 434                 if (actual == tbuf->count) {
 435                         if (debuglevel >= DEBUG_LEVEL_INFO)
 436                                 printk("%s(%d)frame %p completed\n",
 437                                         __FILE__,__LINE__,tbuf);
 438
 439                         /* free current transmit buffer */
 440                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
 441
 442                         /* this tx buffer is done */
 443                         n_hdlc->tbuf = NULL;
 444
 445                         /* wait up sleeping writers */
 446                         wake_up_interruptible(&tty->write_wait);
 447
 448                         /* get next pending transmit buffer */
 449                         tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 450                 } else {
 451                         if (debuglevel >= DEBUG_LEVEL_INFO)
 452                                 printk("%s(%d)frame %p pending\n",
 453                                         __FILE__,__LINE__,tbuf);
 454
 455                         /* buffer not accepted by driver */
 456                         /* set this buffer as pending buffer */
 457                         n_hdlc->tbuf = tbuf;
 458                         break;
 459                 }
 460         }
 461
 462         if (!tbuf)
 463                 tty->flags  &= ~(1 << TTY_DO_WRITE_WAKEUP);
 464
 465         /* Clear the re-entry flag */
 466         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 467         n_hdlc->tbusy = 0;
 468         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 469
 470         if (n_hdlc->woke_up)
 471           goto check_again;
 472
 473         if (debuglevel >= DEBUG_LEVEL_INFO)
 474                 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
 475
 476 }       /* end of n_hdlc_send_frames() */
 477
 478 /**
 479  * n_hdlc_tty_wakeup - Callback for transmit wakeup
 480  * @tty - pointer to associated tty instance data
 481  *
 482  * Called when low level device driver can accept more send data.
 483  */
 484 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
 485 {
 486         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 487
 488         if (debuglevel >= DEBUG_LEVEL_INFO)
 489                 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
 490
 491         if (!n_hdlc)
 492                 return;
 493
 494         if (tty != n_hdlc->tty) {
 495                 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
 496                 return;
 497         }
 498
 499         n_hdlc_send_frames (n_hdlc, tty);
 500
 501 }       /* end of n_hdlc_tty_wakeup() */
 502
 503 /**
 504  * n_hdlc_tty_receive - Called by tty driver when receive data is available
 505  * @tty - pointer to tty instance data
 506  * @data - pointer to received data
 507  * @flags - pointer to flags for data
 508  * @count - count of received data in bytes
 509  *
 510  * Called by tty low level driver when receive data is available. Data is
 511  * interpreted as one HDLC frame.
 512  */
 513 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
 514                                char *flags, int count)
 515 {
 516         register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 517         register struct n_hdlc_buf *buf;
 518
 519         if (debuglevel >= DEBUG_LEVEL_INFO)
 520                 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
 521                         __FILE__,__LINE__, count);
 522
 523         /* This can happen if stuff comes in on the backup tty */
 524         if (!n_hdlc || tty != n_hdlc->tty)
 525                 return;
 526
 527         /* verify line is using HDLC discipline */
 528         if (n_hdlc->magic != HDLC_MAGIC) {
 529                 printk("%s(%d) line not using HDLC discipline\n",
 530                         __FILE__,__LINE__);
 531                 return;
 532         }
 533
 534         if ( count>maxframe ) {
 535                 if (debuglevel >= DEBUG_LEVEL_INFO)
 536                         printk("%s(%d) rx count>maxframesize, data discarded\n",
 537                                __FILE__,__LINE__);
 538                 return;
 539         }
 540
 541         /* get a free HDLC buffer */
 542         buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
 543         if (!buf) {
 544                 /* no buffers in free list, attempt to allocate another rx buffer */
 545                 /* unless the maximum count has been reached */
 546                 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
 547                         buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
 548         }
 549
 550         if (!buf) {
 551                 if (debuglevel >= DEBUG_LEVEL_INFO)
 552                         printk("%s(%d) no more rx buffers, data discarded\n",
 553                                __FILE__,__LINE__);
 554                 return;
 555         }
 556
 557         /* copy received data to HDLC buffer */
 558         memcpy(buf->buf,data,count);
 559         buf->count=count;
 560
 561         /* add HDLC buffer to list of received frames */
 562         n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
 563
 564         /* wake up any blocked reads and perform async signalling */
 565         wake_up_interruptible (&tty->read_wait);
 566         if (n_hdlc->tty->fasync != NULL)
 567                 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
 568
 569 }       /* end of n_hdlc_tty_receive() */
 570
 571 /**
 572  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
 573  * @tty - pointer to tty instance data
 574  * @file - pointer to open file object
 575  * @buf - pointer to returned data buffer
 576  * @nr - size of returned data buffer
 577  *
 578  * Returns the number of bytes returned or error code.
 579  */
 580 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 581                            __u8 __user *buf, size_t nr)
 582 {
 583         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 584         int ret;
 585         struct n_hdlc_buf *rbuf;
 586
 587         if (debuglevel >= DEBUG_LEVEL_INFO)
 588                 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
 589
 590         /* Validate the pointers */
 591         if (!n_hdlc)
 592                 return -EIO;
 593
 594         /* verify user access to buffer */
 595         if (!access_ok(VERIFY_WRITE, buf, nr)) {
 596                 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
 597                 "buffer\n", __FILE__, __LINE__);
 598                 return -EFAULT;
 599         }
 600
 601         tty_lock();
 602
 603         for (;;) {
 604                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
 605                         tty_unlock();
 606                         return -EIO;
 607                 }
 608
 609                 n_hdlc = tty2n_hdlc (tty);
 610                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
 611                          tty != n_hdlc->tty) {
 612                         tty_unlock();
 613                         return 0;
 614                 }
 615
 616                 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
 617                 if (rbuf)
 618                         break;
 619
 620                 /* no data */
 621                 if (file->f_flags & O_NONBLOCK) {
 622                         tty_unlock();
 623                         return -EAGAIN;
 624                 }
 625
 626                 interruptible_sleep_on (&tty->read_wait);
 627                 if (signal_pending(current)) {
 628                         tty_unlock();
 629                         return -EINTR;
 630                 }
 631         }
 632
 633         if (rbuf->count > nr)
 634                 /* frame too large for caller's buffer (discard frame) */
 635                 ret = -EOVERFLOW;
 636         else {
 637                 /* Copy the data to the caller's buffer */
 638                 if (copy_to_user(buf, rbuf->buf, rbuf->count))
 639                         ret = -EFAULT;
 640                 else
 641                         ret = rbuf->count;
 642         }
 643
 644         /* return HDLC buffer to free list unless the free list */
 645         /* count has exceeded the default value, in which case the */
 646         /* buffer is freed back to the OS to conserve memory */
 647         if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
 648                 kfree(rbuf);
 649         else
 650                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
 651         tty_unlock();
 652         return ret;
 653
 654 }       /* end of n_hdlc_tty_read() */
 655
 656 /**
 657  * n_hdlc_tty_write - write a single frame of data to device
 658  * @tty - pointer to associated tty device instance data
 659  * @file - pointer to file object data
 660  * @data - pointer to transmit data (one frame)
 661  * @count - size of transmit frame in bytes
 662  *
 663  * Returns the number of bytes written (or error code).
 664  */
 665 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 666                             const unsigned char *data, size_t count)
 667 {
 668         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 669         int error = 0;
 670         DECLARE_WAITQUEUE(wait, current);
 671         struct n_hdlc_buf *tbuf;
 672
 673         if (debuglevel >= DEBUG_LEVEL_INFO)
 674                 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
 675                         __FILE__,__LINE__,count);
 676
 677         /* Verify pointers */
 678         if (!n_hdlc)
 679                 return -EIO;
 680
 681         if (n_hdlc->magic != HDLC_MAGIC)
 682                 return -EIO;
 683
 684         /* verify frame size */
 685         if (count > maxframe ) {
 686                 if (debuglevel & DEBUG_LEVEL_INFO)
 687                         printk (KERN_WARNING
 688                                 "n_hdlc_tty_write: truncating user packet "
 689                                 "from %lu to %d\n", (unsigned long) count,
 690                                 maxframe );
 691                 count = maxframe;
 692         }
 693
 694         tty_lock();
 695
 696         add_wait_queue(&tty->write_wait, &wait);
 697         set_current_state(TASK_INTERRUPTIBLE);
 698
 699         /* Allocate transmit buffer */
 700         /* sleep until transmit buffer available */
 701         while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
 702                 if (file->f_flags & O_NONBLOCK) {
 703                         error = -EAGAIN;
 704                         break;
 705                 }
 706                 schedule();
 707
 708                 n_hdlc = tty2n_hdlc (tty);
 709                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
 710                     tty != n_hdlc->tty) {
 711                         printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
 712                         error = -EIO;
 713                         break;
 714                 }
 715
 716                 if (signal_pending(current)) {
 717                         error = -EINTR;
 718                         break;
 719                 }
 720         }
 721
 722         set_current_state(TASK_RUNNING);
 723         remove_wait_queue(&tty->write_wait, &wait);
 724
 725         if (!error) {
 726                 /* Retrieve the user's buffer */
 727                 memcpy(tbuf->buf, data, count);
 728
 729                 /* Send the data */
 730                 tbuf->count = error = count;
 731                 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
 732                 n_hdlc_send_frames(n_hdlc,tty);
 733         }
 734         tty_unlock();
 735         return error;
 736
 737 }       /* end of n_hdlc_tty_write() */
 738
 739 /**
 740  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
 741  * @tty - pointer to tty instance data
 742  * @file - pointer to open file object for device
 743  * @cmd - IOCTL command code
 744  * @arg - argument for IOCTL call (cmd dependent)
 745  *
 746  * Returns command dependent result.
 747  */
 748 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 749                             unsigned int cmd, unsigned long arg)
 750 {
 751         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 752         int error = 0;
 753         int count;
 754         unsigned long flags;
 755
 756         if (debuglevel >= DEBUG_LEVEL_INFO)
 757                 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
 758                         __FILE__,__LINE__,cmd);
 759
 760         /* Verify the status of the device */
 761         if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
 762                 return -EBADF;
 763
 764         switch (cmd) {
 765         case FIONREAD:
 766                 /* report count of read data available */
 767                 /* in next available frame (if any) */
 768                 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
 769                 if (n_hdlc->rx_buf_list.head)
 770                         count = n_hdlc->rx_buf_list.head->count;
 771                 else
 772                         count = 0;
 773                 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
 774                 error = put_user(count, (int __user *)arg);
 775                 break;
 776
 777         case TIOCOUTQ:
 778                 /* get the pending tx byte count in the driver */
 779                 count = tty_chars_in_buffer(tty);
 780                 /* add size of next output frame in queue */
 781                 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
 782                 if (n_hdlc->tx_buf_list.head)
 783                         count += n_hdlc->tx_buf_list.head->count;
 784                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
 785                 error = put_user(count, (int __user *)arg);
 786                 break;
 787
 788         case TCFLSH:
 789                 switch (arg) {
 790                 case TCIOFLUSH:
 791                 case TCOFLUSH:
 792                         flush_tx_queue(tty);
 793                 }
 794                 /* fall through to default */
 795
 796         default:
 797                 error = n_tty_ioctl_helper(tty, file, cmd, arg);
 798                 break;
 799         }
 800         return error;
 801
 802 }       /* end of n_hdlc_tty_ioctl() */
 803
 804 /**
 805  * n_hdlc_tty_poll - TTY callback for poll system call
 806  * @tty - pointer to tty instance data
 807  * @filp - pointer to open file object for device
 808  * @poll_table - wait queue for operations
 809  *
 810  * Determine which operations (read/write) will not block and return info
 811  * to caller.
 812  * Returns a bit mask containing info on which ops will not block.
 813  */
 814 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
 815                                     poll_table *wait)
 816 {
 817         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 818         unsigned int mask = 0;
 819
 820         if (debuglevel >= DEBUG_LEVEL_INFO)
 821                 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
 822
 823         if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
 824                 /* queue current process into any wait queue that */
 825                 /* may awaken in the future (read and write) */
 826
 827                 poll_wait(filp, &tty->read_wait, wait);
 828                 poll_wait(filp, &tty->write_wait, wait);
 829
 830                 /* set bits for operations that won't block */
 831                 if (n_hdlc->rx_buf_list.head)
 832                         mask |= POLLIN | POLLRDNORM;    /* readable */
 833                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 834                         mask |= POLLHUP;
 835                 if (tty_hung_up_p(filp))
 836                         mask |= POLLHUP;
 837                 if (!tty_is_writelocked(tty) &&
 838                                 n_hdlc->tx_free_buf_list.head)
 839                         mask |= POLLOUT | POLLWRNORM;   /* writable */
 840         }
 841         return mask;
 842 }       /* end of n_hdlc_tty_poll() */
 843
 844 /**
 845  * n_hdlc_alloc - allocate an n_hdlc instance data structure
 846  *
 847  * Returns a pointer to newly created structure if success, otherwise %NULL
 848  */
 849 static struct n_hdlc *n_hdlc_alloc(void)
 850 {
 851         struct n_hdlc_buf *buf;
 852         int i;
 853         struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
 854
 855         if (!n_hdlc)
 856                 return NULL;
 857
 858         memset(n_hdlc, 0, sizeof(*n_hdlc));
 859
 860         n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
 861         n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
 862         n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
 863         n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
 864
 865         /* allocate free rx buffer list */
 866         for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
 867                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
 868                 if (buf)
 869                         n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
 870                 else if (debuglevel >= DEBUG_LEVEL_INFO)
 871                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
 872         }
 873
 874         /* allocate free tx buffer list */
 875         for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
 876                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
 877                 if (buf)
 878                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
 879                 else if (debuglevel >= DEBUG_LEVEL_INFO)
 880                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
 881         }
 882
 883         /* Initialize the control block */
 884         n_hdlc->magic  = HDLC_MAGIC;
 885         n_hdlc->flags  = 0;
 886
 887         return n_hdlc;
 888
 889 }       /* end of n_hdlc_alloc() */
 890
 891 /**
 892  * n_hdlc_buf_list_init - initialize specified HDLC buffer list
 893  * @list - pointer to buffer list
 894  */
 895 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
 896 {
 897         memset(list, 0, sizeof(*list));
 898         spin_lock_init(&list->spinlock);
 899 }       /* end of n_hdlc_buf_list_init() */
 900
 901 /**
 902  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
 903  * @list - pointer to buffer list
 904  * @buf - pointer to buffer
 905  */
 906 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
 907                            struct n_hdlc_buf *buf)
 908 {
 909         unsigned long flags;
 910         spin_lock_irqsave(&list->spinlock,flags);
 911
 912         buf->link=NULL;
 913         if (list->tail)
 914                 list->tail->link = buf;
 915         else
 916                 list->head = buf;
 917         list->tail = buf;
 918         (list->count)++;
 919
 920         spin_unlock_irqrestore(&list->spinlock,flags);
 921
 922 }       /* end of n_hdlc_buf_put() */
 923
 924 /**
 925  * n_hdlc_buf_get - remove and return an HDLC buffer from list
 926  * @list - pointer to HDLC buffer list
 927  *
 928  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
 929  * list.
 930  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
 931  */
 932 static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
 933 {
 934         unsigned long flags;
 935         struct n_hdlc_buf *buf;
 936         spin_lock_irqsave(&list->spinlock,flags);
 937
 938         buf = list->head;
 939         if (buf) {
 940                 list->head = buf->link;
 941                 (list->count)--;
 942         }
 943         if (!list->head)
 944                 list->tail = NULL;
 945
 946         spin_unlock_irqrestore(&list->spinlock,flags);
 947         return buf;
 948
 949 }       /* end of n_hdlc_buf_get() */
 950
 951 static char hdlc_banner[] __initdata =
 952         KERN_INFO "HDLC line discipline maxframe=%u\n";
 953 static char hdlc_register_ok[] __initdata =
 954         KERN_INFO "N_HDLC line discipline registered.\n";
 955 static char hdlc_register_fail[] __initdata =
 956         KERN_ERR "error registering line discipline: %d\n";
 957 static char hdlc_init_fail[] __initdata =
 958         KERN_INFO "N_HDLC: init failure %d\n";
 959
 960 static int __init n_hdlc_init(void)
 961 {
 962         int status;
 963
 964         /* range check maxframe arg */
 965         if (maxframe < 4096)
 966                 maxframe = 4096;
 967         else if (maxframe > 65535)
 968                 maxframe = 65535;
 969
 970         printk(hdlc_banner, maxframe);
 971
 972         status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
 973         if (!status)
 974                 printk(hdlc_register_ok);
 975         else
 976                 printk(hdlc_register_fail, status);
 977
 978         if (status)
 979                 printk(hdlc_init_fail, status);
 980         return status;
 981
 982 }       /* end of init_module() */
 983
 984 static char hdlc_unregister_ok[] __exitdata =
 985         KERN_INFO "N_HDLC: line discipline unregistered\n";
 986 static char hdlc_unregister_fail[] __exitdata =
 987         KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
 988
 989 static void __exit n_hdlc_exit(void)
 990 {
 991         /* Release tty registration of line discipline */
 992         int status = tty_unregister_ldisc(N_HDLC);
 993
 994         if (status)
 995                 printk(hdlc_unregister_fail, status);
 996         else
 997                 printk(hdlc_unregister_ok);
 998 }
 999
1000 module_init(n_hdlc_init);
1001 module_exit(n_hdlc_exit);
1002
1003 MODULE_LICENSE("GPL");
1004 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
1005 module_param(debuglevel, int, 0);
1006 module_param(maxframe, int, 0);
1007 MODULE_ALIAS_LDISC(N_HDLC);