git.oblomov.eu Git - linux-2.6/blob - 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  *
  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/string.h>       /* used in new tty drivers */
 101 #include <linux/signal.h>       /* used in new tty drivers */
 102 #include <linux/if.h>
 103 #include <linux/bitops.h>
 104
 105 #include <asm/system.h>
 106 #include <asm/termios.h>
 107 #include <asm/uaccess.h>
 108
 109 /*
 110  * Buffers for individual HDLC frames
 111  */
 112 #define MAX_HDLC_FRAME_SIZE 65535
 113 #define DEFAULT_RX_BUF_COUNT 10
 114 #define MAX_RX_BUF_COUNT 60
 115 #define DEFAULT_TX_BUF_COUNT 3
 116
 117 struct n_hdlc_buf {
 118         struct n_hdlc_buf *link;
 119         int               count;
 120         char              buf[1];
 121 };
 122
 123 #define N_HDLC_BUF_SIZE (sizeof(struct n_hdlc_buf) + maxframe)
 124
 125 struct n_hdlc_buf_list {
 126         struct n_hdlc_buf *head;
 127         struct n_hdlc_buf *tail;
 128         int               count;
 129         spinlock_t        spinlock;
 130 };
 131
 132 /**
 133  * struct n_hdlc - per device instance data structure
 134  * @magic - magic value for structure
 135  * @flags - miscellaneous control flags
 136  * @tty - ptr to TTY structure
 137  * @backup_tty - TTY to use if tty gets closed
 138  * @tbusy - reentrancy flag for tx wakeup code
 139  * @woke_up - FIXME: describe this field
 140  * @tbuf - currently transmitting tx buffer
 141  * @tx_buf_list - list of pending transmit frame buffers
 142  * @rx_buf_list - list of received frame buffers
 143  * @tx_free_buf_list - list unused transmit frame buffers
 144  * @rx_free_buf_list - list unused received frame buffers
 145  */
 146 struct n_hdlc {
 147         int                     magic;
 148         __u32                   flags;
 149         struct tty_struct       *tty;
 150         struct tty_struct       *backup_tty;
 151         int                     tbusy;
 152         int                     woke_up;
 153         struct n_hdlc_buf       *tbuf;
 154         struct n_hdlc_buf_list  tx_buf_list;
 155         struct n_hdlc_buf_list  rx_buf_list;
 156         struct n_hdlc_buf_list  tx_free_buf_list;
 157         struct n_hdlc_buf_list  rx_free_buf_list;
 158 };
 159
 160 /*
 161  * HDLC buffer list manipulation functions
 162  */
 163 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list);
 164 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
 165                            struct n_hdlc_buf *buf);
 166 static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *list);
 167
 168 /* Local functions */
 169
 170 static struct n_hdlc *n_hdlc_alloc (void);
 171
 172 /* debug level can be set by insmod for debugging purposes */
 173 #define DEBUG_LEVEL_INFO        1
 174 static int debuglevel;
 175
 176 /* max frame size for memory allocations */
 177 static int maxframe = 4096;
 178
 179 /* TTY callbacks */
 180
 181 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 182                            __u8 __user *buf, size_t nr);
 183 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 184                             const unsigned char *buf, size_t nr);
 185 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 186                             unsigned int cmd, unsigned long arg);
 187 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
 188                                     poll_table *wait);
 189 static int n_hdlc_tty_open(struct tty_struct *tty);
 190 static void n_hdlc_tty_close(struct tty_struct *tty);
 191 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *cp,
 192                                char *fp, int count);
 193 static void n_hdlc_tty_wakeup(struct tty_struct *tty);
 194
 195 #define bset(p,b)       ((p)[(b) >> 5] |= (1 << ((b) & 0x1f)))
 196
 197 #define tty2n_hdlc(tty) ((struct n_hdlc *) ((tty)->disc_data))
 198 #define n_hdlc2tty(n_hdlc)      ((n_hdlc)->tty)
 199
 200 static void flush_rx_queue(struct tty_struct *tty)
 201 {
 202         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 203         struct n_hdlc_buf *buf;
 204
 205         while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))
 206                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);
 207 }
 208
 209 static void flush_tx_queue(struct tty_struct *tty)
 210 {
 211         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 212         struct n_hdlc_buf *buf;
 213         unsigned long flags;
 214
 215         while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))
 216                 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);
 217         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 218         if (n_hdlc->tbuf) {
 219                 n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, n_hdlc->tbuf);
 220                 n_hdlc->tbuf = NULL;
 221         }
 222         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 223 }
 224
 225 static struct tty_ldisc_ops n_hdlc_ldisc = {
 226         .owner          = THIS_MODULE,
 227         .magic          = TTY_LDISC_MAGIC,
 228         .name           = "hdlc",
 229         .open           = n_hdlc_tty_open,
 230         .close          = n_hdlc_tty_close,
 231         .read           = n_hdlc_tty_read,
 232         .write          = n_hdlc_tty_write,
 233         .ioctl          = n_hdlc_tty_ioctl,
 234         .poll           = n_hdlc_tty_poll,
 235         .receive_buf    = n_hdlc_tty_receive,
 236         .write_wakeup   = n_hdlc_tty_wakeup,
 237         .flush_buffer   = flush_rx_queue,
 238 };
 239
 240 /**
 241  * n_hdlc_release - release an n_hdlc per device line discipline info structure
 242  * @n_hdlc - per device line discipline info structure
 243  */
 244 static void n_hdlc_release(struct n_hdlc *n_hdlc)
 245 {
 246         struct tty_struct *tty = n_hdlc2tty (n_hdlc);
 247         struct n_hdlc_buf *buf;
 248
 249         if (debuglevel >= DEBUG_LEVEL_INFO)
 250                 printk("%s(%d)n_hdlc_release() called\n",__FILE__,__LINE__);
 251
 252         /* Ensure that the n_hdlcd process is not hanging on select()/poll() */
 253         wake_up_interruptible (&tty->read_wait);
 254         wake_up_interruptible (&tty->write_wait);
 255
 256         if (tty->disc_data == n_hdlc)
 257                 tty->disc_data = NULL;  /* Break the tty->n_hdlc link */
 258
 259         /* Release transmit and receive buffers */
 260         for(;;) {
 261                 buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
 262                 if (buf) {
 263                         kfree(buf);
 264                 } else
 265                         break;
 266         }
 267         for(;;) {
 268                 buf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);
 269                 if (buf) {
 270                         kfree(buf);
 271                 } else
 272                         break;
 273         }
 274         for(;;) {
 275                 buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
 276                 if (buf) {
 277                         kfree(buf);
 278                 } else
 279                         break;
 280         }
 281         for(;;) {
 282                 buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 283                 if (buf) {
 284                         kfree(buf);
 285                 } else
 286                         break;
 287         }
 288         kfree(n_hdlc->tbuf);
 289         kfree(n_hdlc);
 290
 291 }       /* end of n_hdlc_release() */
 292
 293 /**
 294  * n_hdlc_tty_close - line discipline close
 295  * @tty - pointer to tty info structure
 296  *
 297  * Called when the line discipline is changed to something
 298  * else, the tty is closed, or the tty detects a hangup.
 299  */
 300 static void n_hdlc_tty_close(struct tty_struct *tty)
 301 {
 302         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 303
 304         if (debuglevel >= DEBUG_LEVEL_INFO)
 305                 printk("%s(%d)n_hdlc_tty_close() called\n",__FILE__,__LINE__);
 306
 307         if (n_hdlc != NULL) {
 308                 if (n_hdlc->magic != HDLC_MAGIC) {
 309                         printk (KERN_WARNING"n_hdlc: trying to close unopened tty!\n");
 310                         return;
 311                 }
 312 #if defined(TTY_NO_WRITE_SPLIT)
 313                 clear_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
 314 #endif
 315                 tty->disc_data = NULL;
 316                 if (tty == n_hdlc->backup_tty)
 317                         n_hdlc->backup_tty = NULL;
 318                 if (tty != n_hdlc->tty)
 319                         return;
 320                 if (n_hdlc->backup_tty) {
 321                         n_hdlc->tty = n_hdlc->backup_tty;
 322                 } else {
 323                         n_hdlc_release (n_hdlc);
 324                 }
 325         }
 326
 327         if (debuglevel >= DEBUG_LEVEL_INFO)
 328                 printk("%s(%d)n_hdlc_tty_close() success\n",__FILE__,__LINE__);
 329
 330 }       /* end of n_hdlc_tty_close() */
 331
 332 /**
 333  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
 334  * @tty - pointer to tty info structure
 335  *
 336  * Returns 0 if success, otherwise error code
 337  */
 338 static int n_hdlc_tty_open (struct tty_struct *tty)
 339 {
 340         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 341
 342         if (debuglevel >= DEBUG_LEVEL_INFO)
 343                 printk("%s(%d)n_hdlc_tty_open() called (device=%s)\n",
 344                 __FILE__,__LINE__,
 345                 tty->name);
 346
 347         /* There should not be an existing table for this slot. */
 348         if (n_hdlc) {
 349                 printk (KERN_ERR"n_hdlc_tty_open:tty already associated!\n" );
 350                 return -EEXIST;
 351         }
 352
 353         n_hdlc = n_hdlc_alloc();
 354         if (!n_hdlc) {
 355                 printk (KERN_ERR "n_hdlc_alloc failed\n");
 356                 return -ENFILE;
 357         }
 358
 359         tty->disc_data = n_hdlc;
 360         n_hdlc->tty    = tty;
 361         tty->receive_room = 65536;
 362
 363 #if defined(TTY_NO_WRITE_SPLIT)
 364         /* change tty_io write() to not split large writes into 8K chunks */
 365         set_bit(TTY_NO_WRITE_SPLIT,&tty->flags);
 366 #endif
 367
 368         /* flush receive data from driver */
 369         tty_driver_flush_buffer(tty);
 370
 371         if (debuglevel >= DEBUG_LEVEL_INFO)
 372                 printk("%s(%d)n_hdlc_tty_open() success\n",__FILE__,__LINE__);
 373
 374         return 0;
 375
 376 }       /* end of n_tty_hdlc_open() */
 377
 378 /**
 379  * n_hdlc_send_frames - send frames on pending send buffer list
 380  * @n_hdlc - pointer to ldisc instance data
 381  * @tty - pointer to tty instance data
 382  *
 383  * Send frames on pending send buffer list until the driver does not accept a
 384  * frame (busy) this function is called after adding a frame to the send buffer
 385  * list and by the tty wakeup callback.
 386  */
 387 static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
 388 {
 389         register int actual;
 390         unsigned long flags;
 391         struct n_hdlc_buf *tbuf;
 392
 393         if (debuglevel >= DEBUG_LEVEL_INFO)
 394                 printk("%s(%d)n_hdlc_send_frames() called\n",__FILE__,__LINE__);
 395  check_again:
 396
 397         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 398         if (n_hdlc->tbusy) {
 399                 n_hdlc->woke_up = 1;
 400                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 401                 return;
 402         }
 403         n_hdlc->tbusy = 1;
 404         n_hdlc->woke_up = 0;
 405         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 406
 407         /* get current transmit buffer or get new transmit */
 408         /* buffer from list of pending transmit buffers */
 409
 410         tbuf = n_hdlc->tbuf;
 411         if (!tbuf)
 412                 tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 413
 414         while (tbuf) {
 415                 if (debuglevel >= DEBUG_LEVEL_INFO)
 416                         printk("%s(%d)sending frame %p, count=%d\n",
 417                                 __FILE__,__LINE__,tbuf,tbuf->count);
 418
 419                 /* Send the next block of data to device */
 420                 tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
 421                 actual = tty->ops->write(tty, tbuf->buf, tbuf->count);
 422
 423                 /* rollback was possible and has been done */
 424                 if (actual == -ERESTARTSYS) {
 425                         n_hdlc->tbuf = tbuf;
 426                         break;
 427                 }
 428                 /* if transmit error, throw frame away by */
 429                 /* pretending it was accepted by driver */
 430                 if (actual < 0)
 431                         actual = tbuf->count;
 432
 433                 if (actual == tbuf->count) {
 434                         if (debuglevel >= DEBUG_LEVEL_INFO)
 435                                 printk("%s(%d)frame %p completed\n",
 436                                         __FILE__,__LINE__,tbuf);
 437
 438                         /* free current transmit buffer */
 439                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);
 440
 441                         /* this tx buffer is done */
 442                         n_hdlc->tbuf = NULL;
 443
 444                         /* wait up sleeping writers */
 445                         wake_up_interruptible(&tty->write_wait);
 446
 447                         /* get next pending transmit buffer */
 448                         tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
 449                 } else {
 450                         if (debuglevel >= DEBUG_LEVEL_INFO)
 451                                 printk("%s(%d)frame %p pending\n",
 452                                         __FILE__,__LINE__,tbuf);
 453
 454                         /* buffer not accepted by driver */
 455                         /* set this buffer as pending buffer */
 456                         n_hdlc->tbuf = tbuf;
 457                         break;
 458                 }
 459         }
 460
 461         if (!tbuf)
 462                 tty->flags  &= ~(1 << TTY_DO_WRITE_WAKEUP);
 463
 464         /* Clear the re-entry flag */
 465         spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
 466         n_hdlc->tbusy = 0;
 467         spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
 468
 469         if (n_hdlc->woke_up)
 470           goto check_again;
 471
 472         if (debuglevel >= DEBUG_LEVEL_INFO)
 473                 printk("%s(%d)n_hdlc_send_frames() exit\n",__FILE__,__LINE__);
 474
 475 }       /* end of n_hdlc_send_frames() */
 476
 477 /**
 478  * n_hdlc_tty_wakeup - Callback for transmit wakeup
 479  * @tty - pointer to associated tty instance data
 480  *
 481  * Called when low level device driver can accept more send data.
 482  */
 483 static void n_hdlc_tty_wakeup(struct tty_struct *tty)
 484 {
 485         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 486
 487         if (debuglevel >= DEBUG_LEVEL_INFO)
 488                 printk("%s(%d)n_hdlc_tty_wakeup() called\n",__FILE__,__LINE__);
 489
 490         if (!n_hdlc)
 491                 return;
 492
 493         if (tty != n_hdlc->tty) {
 494                 tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
 495                 return;
 496         }
 497
 498         n_hdlc_send_frames (n_hdlc, tty);
 499
 500 }       /* end of n_hdlc_tty_wakeup() */
 501
 502 /**
 503  * n_hdlc_tty_receive - Called by tty driver when receive data is available
 504  * @tty - pointer to tty instance data
 505  * @data - pointer to received data
 506  * @flags - pointer to flags for data
 507  * @count - count of received data in bytes
 508  *
 509  * Called by tty low level driver when receive data is available. Data is
 510  * interpreted as one HDLC frame.
 511  */
 512 static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
 513                                char *flags, int count)
 514 {
 515         register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 516         register struct n_hdlc_buf *buf;
 517
 518         if (debuglevel >= DEBUG_LEVEL_INFO)
 519                 printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
 520                         __FILE__,__LINE__, count);
 521
 522         /* This can happen if stuff comes in on the backup tty */
 523         if (!n_hdlc || tty != n_hdlc->tty)
 524                 return;
 525
 526         /* verify line is using HDLC discipline */
 527         if (n_hdlc->magic != HDLC_MAGIC) {
 528                 printk("%s(%d) line not using HDLC discipline\n",
 529                         __FILE__,__LINE__);
 530                 return;
 531         }
 532
 533         if ( count>maxframe ) {
 534                 if (debuglevel >= DEBUG_LEVEL_INFO)
 535                         printk("%s(%d) rx count>maxframesize, data discarded\n",
 536                                __FILE__,__LINE__);
 537                 return;
 538         }
 539
 540         /* get a free HDLC buffer */
 541         buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
 542         if (!buf) {
 543                 /* no buffers in free list, attempt to allocate another rx buffer */
 544                 /* unless the maximum count has been reached */
 545                 if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
 546                         buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
 547         }
 548
 549         if (!buf) {
 550                 if (debuglevel >= DEBUG_LEVEL_INFO)
 551                         printk("%s(%d) no more rx buffers, data discarded\n",
 552                                __FILE__,__LINE__);
 553                 return;
 554         }
 555
 556         /* copy received data to HDLC buffer */
 557         memcpy(buf->buf,data,count);
 558         buf->count=count;
 559
 560         /* add HDLC buffer to list of received frames */
 561         n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
 562
 563         /* wake up any blocked reads and perform async signalling */
 564         wake_up_interruptible (&tty->read_wait);
 565         if (n_hdlc->tty->fasync != NULL)
 566                 kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);
 567
 568 }       /* end of n_hdlc_tty_receive() */
 569
 570 /**
 571  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
 572  * @tty - pointer to tty instance data
 573  * @file - pointer to open file object
 574  * @buf - pointer to returned data buffer
 575  * @nr - size of returned data buffer
 576  *
 577  * Returns the number of bytes returned or error code.
 578  */
 579 static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
 580                            __u8 __user *buf, size_t nr)
 581 {
 582         struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
 583         int ret;
 584         struct n_hdlc_buf *rbuf;
 585
 586         if (debuglevel >= DEBUG_LEVEL_INFO)
 587                 printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
 588
 589         /* Validate the pointers */
 590         if (!n_hdlc)
 591                 return -EIO;
 592
 593         /* verify user access to buffer */
 594         if (!access_ok(VERIFY_WRITE, buf, nr)) {
 595                 printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
 596                 "buffer\n", __FILE__, __LINE__);
 597                 return -EFAULT;
 598         }
 599
 600         lock_kernel();
 601
 602         for (;;) {
 603                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
 604                         unlock_kernel();
 605                         return -EIO;
 606                 }
 607
 608                 n_hdlc = tty2n_hdlc (tty);
 609                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
 610                          tty != n_hdlc->tty) {
 611                         unlock_kernel();
 612                         return 0;
 613                 }
 614
 615                 rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
 616                 if (rbuf)
 617                         break;
 618
 619                 /* no data */
 620                 if (file->f_flags & O_NONBLOCK) {
 621                         unlock_kernel();
 622                         return -EAGAIN;
 623                 }
 624
 625                 interruptible_sleep_on (&tty->read_wait);
 626                 if (signal_pending(current)) {
 627                         unlock_kernel();
 628                         return -EINTR;
 629                 }
 630         }
 631
 632         if (rbuf->count > nr)
 633                 /* frame too large for caller's buffer (discard frame) */
 634                 ret = -EOVERFLOW;
 635         else {
 636                 /* Copy the data to the caller's buffer */
 637                 if (copy_to_user(buf, rbuf->buf, rbuf->count))
 638                         ret = -EFAULT;
 639                 else
 640                         ret = rbuf->count;
 641         }
 642
 643         /* return HDLC buffer to free list unless the free list */
 644         /* count has exceeded the default value, in which case the */
 645         /* buffer is freed back to the OS to conserve memory */
 646         if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
 647                 kfree(rbuf);
 648         else
 649                 n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
 650         unlock_kernel();
 651         return ret;
 652
 653 }       /* end of n_hdlc_tty_read() */
 654
 655 /**
 656  * n_hdlc_tty_write - write a single frame of data to device
 657  * @tty - pointer to associated tty device instance data
 658  * @file - pointer to file object data
 659  * @data - pointer to transmit data (one frame)
 660  * @count - size of transmit frame in bytes
 661  *
 662  * Returns the number of bytes written (or error code).
 663  */
 664 static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
 665                             const unsigned char *data, size_t count)
 666 {
 667         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 668         int error = 0;
 669         DECLARE_WAITQUEUE(wait, current);
 670         struct n_hdlc_buf *tbuf;
 671
 672         if (debuglevel >= DEBUG_LEVEL_INFO)
 673                 printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
 674                         __FILE__,__LINE__,count);
 675
 676         /* Verify pointers */
 677         if (!n_hdlc)
 678                 return -EIO;
 679
 680         if (n_hdlc->magic != HDLC_MAGIC)
 681                 return -EIO;
 682
 683         /* verify frame size */
 684         if (count > maxframe ) {
 685                 if (debuglevel & DEBUG_LEVEL_INFO)
 686                         printk (KERN_WARNING
 687                                 "n_hdlc_tty_write: truncating user packet "
 688                                 "from %lu to %d\n", (unsigned long) count,
 689                                 maxframe );
 690                 count = maxframe;
 691         }
 692
 693         lock_kernel();
 694
 695         add_wait_queue(&tty->write_wait, &wait);
 696         set_current_state(TASK_INTERRUPTIBLE);
 697
 698         /* Allocate transmit buffer */
 699         /* sleep until transmit buffer available */
 700         while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
 701                 if (file->f_flags & O_NONBLOCK) {
 702                         error = -EAGAIN;
 703                         break;
 704                 }
 705                 schedule();
 706
 707                 n_hdlc = tty2n_hdlc (tty);
 708                 if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
 709                     tty != n_hdlc->tty) {
 710                         printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
 711                         error = -EIO;
 712                         break;
 713                 }
 714
 715                 if (signal_pending(current)) {
 716                         error = -EINTR;
 717                         break;
 718                 }
 719         }
 720
 721         set_current_state(TASK_RUNNING);
 722         remove_wait_queue(&tty->write_wait, &wait);
 723
 724         if (!error) {
 725                 /* Retrieve the user's buffer */
 726                 memcpy(tbuf->buf, data, count);
 727
 728                 /* Send the data */
 729                 tbuf->count = error = count;
 730                 n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
 731                 n_hdlc_send_frames(n_hdlc,tty);
 732         }
 733         unlock_kernel();
 734         return error;
 735
 736 }       /* end of n_hdlc_tty_write() */
 737
 738 /**
 739  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
 740  * @tty - pointer to tty instance data
 741  * @file - pointer to open file object for device
 742  * @cmd - IOCTL command code
 743  * @arg - argument for IOCTL call (cmd dependent)
 744  *
 745  * Returns command dependent result.
 746  */
 747 static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
 748                             unsigned int cmd, unsigned long arg)
 749 {
 750         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 751         int error = 0;
 752         int count;
 753         unsigned long flags;
 754
 755         if (debuglevel >= DEBUG_LEVEL_INFO)
 756                 printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
 757                         __FILE__,__LINE__,cmd);
 758
 759         /* Verify the status of the device */
 760         if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
 761                 return -EBADF;
 762
 763         switch (cmd) {
 764         case FIONREAD:
 765                 /* report count of read data available */
 766                 /* in next available frame (if any) */
 767                 spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
 768                 if (n_hdlc->rx_buf_list.head)
 769                         count = n_hdlc->rx_buf_list.head->count;
 770                 else
 771                         count = 0;
 772                 spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
 773                 error = put_user(count, (int __user *)arg);
 774                 break;
 775
 776         case TIOCOUTQ:
 777                 /* get the pending tx byte count in the driver */
 778                 count = tty_chars_in_buffer(tty);
 779                 /* add size of next output frame in queue */
 780                 spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
 781                 if (n_hdlc->tx_buf_list.head)
 782                         count += n_hdlc->tx_buf_list.head->count;
 783                 spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
 784                 error = put_user(count, (int __user *)arg);
 785                 break;
 786
 787         case TCFLSH:
 788                 switch (arg) {
 789                 case TCIOFLUSH:
 790                 case TCOFLUSH:
 791                         flush_tx_queue(tty);
 792                 }
 793                 /* fall through to default */
 794
 795         default:
 796                 error = n_tty_ioctl_helper(tty, file, cmd, arg);
 797                 break;
 798         }
 799         return error;
 800
 801 }       /* end of n_hdlc_tty_ioctl() */
 802
 803 /**
 804  * n_hdlc_tty_poll - TTY callback for poll system call
 805  * @tty - pointer to tty instance data
 806  * @filp - pointer to open file object for device
 807  * @poll_table - wait queue for operations
 808  *
 809  * Determine which operations (read/write) will not block and return info
 810  * to caller.
 811  * Returns a bit mask containing info on which ops will not block.
 812  */
 813 static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
 814                                     poll_table *wait)
 815 {
 816         struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
 817         unsigned int mask = 0;
 818
 819         if (debuglevel >= DEBUG_LEVEL_INFO)
 820                 printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
 821
 822         if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
 823                 /* queue current process into any wait queue that */
 824                 /* may awaken in the future (read and write) */
 825
 826                 poll_wait(filp, &tty->read_wait, wait);
 827                 poll_wait(filp, &tty->write_wait, wait);
 828
 829                 /* set bits for operations that won't block */
 830                 if (n_hdlc->rx_buf_list.head)
 831                         mask |= POLLIN | POLLRDNORM;    /* readable */
 832                 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
 833                         mask |= POLLHUP;
 834                 if (tty_hung_up_p(filp))
 835                         mask |= POLLHUP;
 836                 if (!tty_is_writelocked(tty) &&
 837                                 n_hdlc->tx_free_buf_list.head)
 838                         mask |= POLLOUT | POLLWRNORM;   /* writable */
 839         }
 840         return mask;
 841 }       /* end of n_hdlc_tty_poll() */
 842
 843 /**
 844  * n_hdlc_alloc - allocate an n_hdlc instance data structure
 845  *
 846  * Returns a pointer to newly created structure if success, otherwise %NULL
 847  */
 848 static struct n_hdlc *n_hdlc_alloc(void)
 849 {
 850         struct n_hdlc_buf *buf;
 851         int i;
 852         struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);
 853
 854         if (!n_hdlc)
 855                 return NULL;
 856
 857         memset(n_hdlc, 0, sizeof(*n_hdlc));
 858
 859         n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
 860         n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
 861         n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
 862         n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
 863
 864         /* allocate free rx buffer list */
 865         for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
 866                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
 867                 if (buf)
 868                         n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
 869                 else if (debuglevel >= DEBUG_LEVEL_INFO)
 870                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
 871         }
 872
 873         /* allocate free tx buffer list */
 874         for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
 875                 buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
 876                 if (buf)
 877                         n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
 878                 else if (debuglevel >= DEBUG_LEVEL_INFO)
 879                         printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
 880         }
 881
 882         /* Initialize the control block */
 883         n_hdlc->magic  = HDLC_MAGIC;
 884         n_hdlc->flags  = 0;
 885
 886         return n_hdlc;
 887
 888 }       /* end of n_hdlc_alloc() */
 889
 890 /**
 891  * n_hdlc_buf_list_init - initialize specified HDLC buffer list
 892  * @list - pointer to buffer list
 893  */
 894 static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
 895 {
 896         memset(list, 0, sizeof(*list));
 897         spin_lock_init(&list->spinlock);
 898 }       /* end of n_hdlc_buf_list_init() */
 899
 900 /**
 901  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
 902  * @list - pointer to buffer list
 903  * @buf - pointer to buffer
 904  */
 905 static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
 906                            struct n_hdlc_buf *buf)
 907 {
 908         unsigned long flags;
 909         spin_lock_irqsave(&list->spinlock,flags);
 910
 911         buf->link=NULL;
 912         if (list->tail)
 913                 list->tail->link = buf;
 914         else
 915                 list->head = buf;
 916         list->tail = buf;
 917         (list->count)++;
 918
 919         spin_unlock_irqrestore(&list->spinlock,flags);
 920
 921 }       /* end of n_hdlc_buf_put() */
 922
 923 /**
 924  * n_hdlc_buf_get - remove and return an HDLC buffer from list
 925  * @list - pointer to HDLC buffer list
 926  *
 927  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
 928  * list.
 929  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
 930  */
 931 static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
 932 {
 933         unsigned long flags;
 934         struct n_hdlc_buf *buf;
 935         spin_lock_irqsave(&list->spinlock,flags);
 936
 937         buf = list->head;
 938         if (buf) {
 939                 list->head = buf->link;
 940                 (list->count)--;
 941         }
 942         if (!list->head)
 943                 list->tail = NULL;
 944
 945         spin_unlock_irqrestore(&list->spinlock,flags);
 946         return buf;
 947
 948 }       /* end of n_hdlc_buf_get() */
 949
 950 static char hdlc_banner[] __initdata =
 951         KERN_INFO "HDLC line discipline maxframe=%u\n";
 952 static char hdlc_register_ok[] __initdata =
 953         KERN_INFO "N_HDLC line discipline registered.\n";
 954 static char hdlc_register_fail[] __initdata =
 955         KERN_ERR "error registering line discipline: %d\n";
 956 static char hdlc_init_fail[] __initdata =
 957         KERN_INFO "N_HDLC: init failure %d\n";
 958
 959 static int __init n_hdlc_init(void)
 960 {
 961         int status;
 962
 963         /* range check maxframe arg */
 964         if (maxframe < 4096)
 965                 maxframe = 4096;
 966         else if (maxframe > 65535)
 967                 maxframe = 65535;
 968
 969         printk(hdlc_banner, maxframe);
 970
 971         status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
 972         if (!status)
 973                 printk(hdlc_register_ok);
 974         else
 975                 printk(hdlc_register_fail, status);
 976
 977         if (status)
 978                 printk(hdlc_init_fail, status);
 979         return status;
 980
 981 }       /* end of init_module() */
 982
 983 static char hdlc_unregister_ok[] __exitdata =
 984         KERN_INFO "N_HDLC: line discipline unregistered\n";
 985 static char hdlc_unregister_fail[] __exitdata =
 986         KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";
 987
 988 static void __exit n_hdlc_exit(void)
 989 {
 990         /* Release tty registration of line discipline */
 991         int status = tty_unregister_ldisc(N_HDLC);
 992
 993         if (status)
 994                 printk(hdlc_unregister_fail, status);
 995         else
 996                 printk(hdlc_unregister_ok);
 997 }
 998
 999 module_init(n_hdlc_init);
1000 module_exit(n_hdlc_exit);
1001
1002 MODULE_LICENSE("GPL");
1003 MODULE_AUTHOR("Paul Fulghum paulkf@microgate.com");
1004 module_param(debuglevel, int, 0);
1005 module_param(maxframe, int, 0);
1006 MODULE_ALIAS_LDISC(N_HDLC);