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